Science.gov

Sample records for warm magnetized atomic

  1. Warm Vapor Atom Interferometer

    NASA Astrophysics Data System (ADS)

    Biedermann, Grant; Wheeler, David; Jau, Yuan-Yu; McGuinness, Hayden

    2014-05-01

    We present a light pulse atom interferometer using room temperature rubidium vapor. Doppler sensitive stimulated Raman transitions forming the atom optical elements inherently select a cold velocity group for the interferometer. The interferometer is configured to be sensitive to accelerations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Gradient Echo Quantum Memory in Warm Atomic Vapor

    PubMed Central

    Pinel, Olivier; Hosseini, Mahdi; Sparkes, Ben M.; Everett, Jesse L.; Higginbottom, Daniel; Campbell, Geoff T.; Lam, Ping Koy; Buchler, Ben C.

    2013-01-01

    Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain. PMID:24300586

  3. Warm inflation in presence of magnetic fields

    SciTech Connect

    Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia

    2013-07-23

    We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales which rises de possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger's proper time method.

  4. Magnetic Control of Atomic Motion

    NASA Astrophysics Data System (ADS)

    Mazur, Tom; Bannerman, Travis; Chavez, Isaac; Clark, Rob; Libson, Adam; Raizen, Mark

    2010-03-01

    Using a sequence of pulsed electromagnetic coils, known as the atomic coilgun, we slowed supersonic beams of atomic neon and molecular oxygen. We report our progress toward adapting the atomic coilgun for magnetically trapping hydrogen isotopes. This work has motivated us to investigate other methods for magnetic control of atomic motion. We describe these techniques, and present calculations suggesting their utility in controlling atomic motion. We then outline our plans for using these methods in certain applications.

  5. Magnetic remanence in single atoms.

    PubMed

    Donati, F; Rusponi, S; Stepanow, S; Wäckerlin, C; Singha, A; Persichetti, L; Baltic, R; Diller, K; Patthey, F; Fernandes, E; Dreiser, J; Šljivančanin, Ž; Kummer, K; Nistor, C; Gambardella, P; Brune, H

    2016-04-15

    A permanent magnet retains a substantial fraction of its saturation magnetization in the absence of an external magnetic field. Realizing magnetic remanence in a single atom allows for storing and processing information in the smallest unit of matter. We show that individual holmium (Ho) atoms adsorbed on ultrathin MgO(100) layers on Ag(100) exhibit magnetic remanence up to a temperature of 30 kelvin and a relaxation time of 1500 seconds at 10 kelvin. This extraordinary stability is achieved by the realization of a symmetry-protected magnetic ground state and by decoupling the Ho spin from the underlying metal by a tunnel barrier. PMID:27081065

  6. Mass loss from warm giants: Magnetic effects

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1980-01-01

    Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles.

  7. The first single atom magnet

    NASA Astrophysics Data System (ADS)

    Donati, Fabio; Rusponi, Stefano; Wäckerlin, Christian; Singha, Aparajita; Baltic, Romana; Diller, Katharina; Patthey, François; Fernandes, Edgar; Brune, Harald; Dreiser, Jan; Sljivancanin, Zeljko; Kummer, Kurt; Stepanow, Sebastian; Persichetti, Luca; Nistor, Corneliu; Gambardella, Pietro

    The prime feature of a magnet is to retain a significant fraction of its saturation magnetization in the absence of an external magnetic field. Realizing magnetic remanence in a single atom would allow storing and processing information in the smallest unit of matter. Here we show that individual rare-earth atoms on ultrathin insulating layers grown on non-magnetic metal substrates exhibit magnetic remanence and, therefore, are the first magnets formed by a single surface adsorbed atom. These magnets have a magnetic lifetime of 1500 s and a coercive field of 3.7 T at 10 K. In addition, their hysteresis loop remains open up to 30 K. This first example of a single atom magnet shows bistability at a temperature which is significantly higher than the best single molecule magnets reported so far. Its extraordinary stability is achieved by a suitable combination of magnetic ground state and adsorption site symmetry, and by decoupling the 4 f spin from the underlying metal by a tunnel barrier.

  8. Magnetic trap for thulium atoms

    SciTech Connect

    Sukachev, D D; Sokolov, A V; Chebakov, K A; Akimov, A V; Kolachevskii, N N; Sorokin, Vadim N

    2011-08-31

    For the first time ultra-cold thulium atoms were trapped in a magnetic quadrupole trap with a small field gradient (20 Gs cm{sup -1}). The atoms were loaded from a cloud containing 4x10{sup 5} atoms that were preliminarily cooled in a magneto-optical trap to the sub-Doppler temperature of 80 {mu}K. As many as 4x10{sup 4} atoms were trapped in the magnetic trap at the temperature of 40 {mu}K. By the character of trap population decay the lifetime of atoms was determined (0.5 s) and an upper estimate was obtained for the rate constant of inelastic binary collisions for spin-polarised thulium atoms in the ground state (g{sub in} < 10{sup -11}cm{sup 3} s{sup -1}). (magnetic traps)

  9. Atomic and optical properties of warm dense copper.

    PubMed

    Miloshevsky, Gennady; Hassanein, Ahmed

    2015-09-01

    The emission of x rays from warm dense matter is of great interest for both spectroscopic diagnostics and development of intense x-ray sources. We report the results from the collisional-radiative steady-state (CRSS) modeling of atomic and optical properties of copper plasmas at near-solid and solid-state density for a range of temperatures. The CRSS model is validated against the available data on the average charge state and shifts of energy levels in aluminum and the opacity and emissivity spectra of carbon and aluminum plasmas. The average charge states, number density of ion species, and free electrons as a function of temperature are investigated for the solid-density copper plasma. Due to the dense plasma environment the four outer electrons are found to be unbounded even in the low-temperature limit ∼1eV. As the temperature changes from 1 to 100 eV, the predominant species vary from fivefold- to twelvefold-ionized copper ions. The opacity and emissivity spectra of dense copper plasmas are studied using the local thermodynamic equilibrium (LTE) and non-LTE approaches. It is found that the non-LTE effects are important in the spectral region of soft x rays emitted from the K shell. The emissivity in spectral lines is completely suppressed, indicating the importance of the energy-dissipating radiative processes in this soft x-ray region. Line broadening and redshifts of the K- and L-shell spectral lines toward higher wavelengths are observed with the increase of plasma density. These results have important implications for understanding the radiative properties of warm dense copper and can be useful for future experimental studies. PMID:26465577

  10. Topological Superconductivity with Magnetic Atoms

    NASA Astrophysics Data System (ADS)

    Glazman, Leonid

    2015-03-01

    Chains of magnetic impurities embedded in a conventional s-wave superconductor may induce the formation of a topologically non-trivial superconducting phase. If such a phase is formed along a chain, then its ends carry Majorana fermions. We investigate this possibility theoretically by developing a tight-binding Bogoliubov-de Gennes description, starting from the Shiba bound states induced by the individual magnetic impurities. While the resulting Hamiltonian has similarities with the Kitaev model for one-dimensional spinless p-wave superconductors, there are also important differences, most notably the long-range (power-law) nature of hopping and pairing as well as the complex hopping amplitudes. We develop an analytical theory, complemented by numerical approaches, which accounts for the electron long-range pairing and hopping along the chain, inhomogeneous magnetic order in the chain of embedded impurities or spin-orbit coupling in the host superconductor, and the possibility of direct electron hopping between the impurity atoms. This allows us to elucidate the domain of parameters favoring the formation of a topological phase and to find the spatial structure of Majorana states appearing in that phase. This talk is based on joint work with F. von Oppen, Falko Pientka, and Yang Peng.

  11. Warm inflation in the presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Piccinelli, Gabriella; Sánchez, Ángel; Ayala, Alejandro; Mizher, Ana Julia

    2014-10-01

    We study the effects of primordial magnetic fields on the inflationary potential in the context of a warm inflation scenario. The model, based on global supersymmetry with a new-inflation-type potential and a coupling between the inflaton and a heavy intermediate superfield, is already known to preserve the flatness required for slow-roll conditions even after including thermal contributions. Here we show that the magnetic field makes the potential even flatter, retarding the transition and rendering it smoother.

  12. Surface electromagnetic wave equations in a warm magnetized quantum plasma

    SciTech Connect

    Li, Chunhua; Yang, Weihong; Wu, Zhengwei; Chu, Paul K.

    2014-07-15

    Based on the single-fluid plasma model, a theoretical investigation of surface electromagnetic waves in a warm quantum magnetized inhomogeneous plasma is presented. The surface electromagnetic waves are assumed to propagate on the plane between a vacuum and a warm quantum magnetized plasma. The quantum magnetohydrodynamic model includes quantum diffraction effect (Bohm potential), and quantum statistical pressure is used to derive the new dispersion relation of surface electromagnetic waves. And the general dispersion relation is analyzed in some special cases of interest. It is shown that surface plasma oscillations can be propagated due to quantum effects, and the propagation velocity is enhanced. Furthermore, the external magnetic field has a significant effect on surface wave's dispersion equation. Our work should be of a useful tool for investigating the physical characteristic of surface waves and physical properties of the bounded quantum plasmas.

  13. Warm and dense stellar matter under strong magnetic fields

    SciTech Connect

    Rabhi, A.; Panda, P. K.; Providencia, C.

    2011-09-15

    We investigate the effects of strong magnetic fields on the equation of state of warm stellar matter as it may occur in a protoneutron star. Both neutrino-free and neutrino-trapped matter at a fixed entropy per baryon are analyzed. A relativistic mean-field nuclear model, including the possibility of hyperon formation, is considered. A density-dependent magnetic field with a magnitude of 10{sup 15} G at the surface and not more than 3x10{sup 18} G at the center is considered. The magnetic field gives rise to a neutrino suppression, mainly at low densities, in matter with trapped neutrinos. It is shown that a hybrid protoneutron star will not evolve into a low-mass black hole if the magnetic field is strong enough and the magnetic field does not decay. However, the decay of the magnetic field after cooling may give rise to the formation of a low-mass black hole.

  14. Magnetic measurements with atomic-plane resolution.

    PubMed

    Rusz, Ján; Muto, Shunsuke; Spiegelberg, Jakob; Adam, Roman; Tatsumi, Kazuyoshi; Bürgler, Daniel E; Oppeneer, Peter M; Schneider, Claus M

    2016-01-01

    Rapid development of magnetic nanotechnologies calls for experimental techniques capable of providing magnetic information with subnanometre spatial resolution. Available probes of magnetism either detect only surface properties, such as spin-polarized scanning tunnelling microscopy, magnetic force microscopy or spin-polarized low-energy electron microscopy, or they are bulk probes with limited spatial resolution or quantitativeness, such as X-ray magnetic circular dichroism or classical electron magnetic circular dichroism (EMCD). Atomic resolution EMCD methods have been proposed, although not yet experimentally realized. Here, we demonstrate an EMCD technique with an atomic size electron probe utilizing a probe-corrected scanning transmission electron microscope in its standard operation mode. The crucial element of the method is a ramp in the phase of the electron beam wavefunction, introduced by a controlled beam displacement. We detect EMCD signals with atomic-plane resolution, thereby bringing near-atomic resolution magnetic circular dichroism spectroscopy to hundreds of laboratories worldwide. PMID:27578421

  15. Cold atom reflection from curved magnetic mirrors

    NASA Astrophysics Data System (ADS)

    Hughes, Ifan G.; Barton, P. A.; Boshier, M. G.; Hinds, Edward A.

    1997-05-01

    Multiple bounces of cold rubidium atoms have been observed for times up to one second in a trap formed by gravity and a 2 cm-diameter spherical mirror made from a sinusoidally magnetized floppy disk. We have studied the dynamics of the atoms bouncing in this trap from several different heights up to 40.5 mm and we conclude that the atoms are reflected specularly and with reflectivity 1.01(3). Slight roughness of the mirror is caused by harmonics in the magnetization of the surface and by discontinuities at the boundaries between recorded tracks. As the next step in this atom optics program we propose using a magnetic mirror to create a 2D atomic gas. We discuss how cold atoms can be loaded into the ground state of a static magnetic potential well that exists above the surface of the mirror as a consequence of the intermediate-field Zeeman effect.

  16. Large spin magnetism with cold atoms

    NASA Astrophysics Data System (ADS)

    Laburthe-Tolra, Bruno

    2016-05-01

    The properties of quantum gases made of ultra-cold atoms strongly depend on the interactions between atoms. These interactions lead to condensed-matter-like collective behavior, so that quantum gases appear to be a new platform to study quantum many-body physics. In this seminar, I will focus on the case where the atoms possess an internal (spin) degrees of freedom. The spin of atoms is naturally larger than that of electrons. Therefore, the study of the magnetic properties of ultra-cold gases allows for an exploration of magnetism beyond the typical situation in solid-state physics where magnetism is associated to the s = 1/2 spin of the electron. I will describe three specific cases: spinor Bose-Einstein condensates, where spin-dependent contact interactions introduce new quantum phases and spin dynamics; large spin magnetic atoms where strong dipole-dipole interactions lead to exotic quantum magnetism; large spin Fermi gases.

  17. Magnetic whispering-gallery mirror for atoms

    NASA Astrophysics Data System (ADS)

    Bertram, R. P.; Merimeche, H.; Mützel, M.; Metcalf, H.; Haubrich, D.; Meschede, D.; Rosenbusch, P.; Hinds, E. A.

    2001-05-01

    Videotape with a sinusoidal magnetization of 31 μm wavelength is used to reflect Cs atoms with unit reflectivity in a 75 m/s atomic beam. The atoms serve as a probe, allowing us to measure the magnetic field at the surface. A technique is presented for mounting the videotape so that its surface can be curved to a specific shape or made flexible. We show that such a reflector provides high-quality grazing-incidence atom optics and we demonstrate deflections as large as 23 ° in a whispering-gallery geometry.

  18. Warm Magnetic Field Measurements of LARP HQ Magnet

    SciTech Connect

    Caspi, S; Cheng, D; Deitderich, D; Felice, H; Ferracin, P; Hafalia, R; Joseph, J; Lizarazo, J; Martchevskii, M; Nash, C; Sabbi, G L; Vu, C; Schmalzle, J; Ambrosio, G; Bossert, R; Chlachidze, G; DiMarco, J; Kashikhin, V

    2011-03-28

    The US-LHC Accelerator Research Program is developing and testing a high-gradient quadrupole (HQ) magnet, aiming at demonstrating the feasibility of Nb{sub 3}Sn technologies for the LHC luminosity upgrade. The 1 m long HQ magnet has a 120 mm bore with a conductor-limited gradient of 219 T/m at 1.9 K and a peak field of 15 T. HQ includes accelerator features such as alignment and field quality. Here we present the magnetic measurement results obtained at LBNL with a constant current of 30 A. A 100 mm long circuit-board rotating coil developed by FNAL was used and the induced voltage and flux increment were acquired. The measured b{sub 6} ranges from 0.3 to 0.5 units in the magnet straight section at a reference radius of 21.55 mm. The data reduced from the numerical integration of the raw voltage agree with those from the fast digital integrators.

  19. Atom optics with permanent magnetic components

    NASA Astrophysics Data System (ADS)

    Meschede, Dieter; Bloch, Immanuel; Goepfert, A.; Haubrich, D.; Kreis, M.; Lison, F.; Schuetze, R.; Wynands, Robert

    1997-05-01

    We have fabricated and investigated efficient magnetic lenses, waveguides, and mirrors from rare earth permanent materials. They are affordable and maintenance free. In contrast to corresponding light force components they do not need any supplies, they have large apertures, high reflectivity, and there is no spontaneous emission. The cylindrical shape of magnetic components is furthermore well suited to steer atomic beams.

  20. Ladder-type electromagnetically induced transparency using nanofiber-guided light in a warm atomic vapor

    NASA Astrophysics Data System (ADS)

    Jones, D. E.; Franson, J. D.; Pittman, T. B.

    2015-10-01

    We demonstrate ladder-type electromagnetically induced transparency (EIT) using an optical nanofiber suspended in a warm rubidium vapor. The signal and control fields are both guided along the nanofiber, which enables strong nonlinear interactions with the surrounding atoms at relatively low powers. Transit-time broadening is found to be a significant EIT decoherence mechanism in this tightly confined waveguiding geometry. Nonetheless, we observe significant EIT and controlled polarization rotation using control-field powers of only a few microwatts in this relatively robust warm-atom nanofiber system.

  1. Analysis of a magnetically trapped atom clock

    SciTech Connect

    Kadio, D.; Band, Y. B.

    2006-11-15

    We consider optimization of a rubidium atom clock that uses magnetically trapped Bose condensed atoms in a highly elongated trap, and determine the optimal conditions for minimum Allan variance of the clock using microwave Ramsey fringe spectroscopy. Elimination of magnetic field shifts and collisional shifts are considered. The effects of spin-dipolar relaxation are addressed in the optimization of the clock. We find that for the interstate interaction strength equal to or larger than the intrastate interaction strengths, a modulational instability results in phase separation and symmetry breaking of the two-component condensate composed of the ground and excited hyperfine clock levels, and this mechanism limits the clock accuracy.

  2. Application of atomic magnetometry in magnetic particledetection

    SciTech Connect

    Xu, Shoujun; Donaldson, Marcus H.; Pines, Alexander; Rochester,Simon M.; Budker, Dmitry; Yashchuk, Valeriy V.

    2006-09-17

    We demonstrate the detection of magnetic particles carriedby water in a continuous flow using an atomic magnetic gradiometer.Studies on three types of magnetic particles are presented: a singlecobalt particle (diameter ~;150 mum, multi-domain), a suspension ofsuperparamagnetic magnetite particles (diameter ~;1 mum), andferromagnetic cobalt nanoparticles (diameter ~;10 nm, 120 kA/mmagnetization). Estimated detection limits are 20 mum diameter for asingle cobalt particle at a water flow rate 30 ml/min, 5x103 magnetiteparticles at 160 ml/min, and 50 pl for the specific ferromagnetic fluidat 130 ml/min. Possible applications of our method arediscussed.

  3. Cold Rydberg atoms in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Guest, J. R.; Choi, J.-H.; Povilus, A.; Raithel, G.

    2003-05-01

    The combination of laser-cooling and trapping methods with Rydberg-atom spectroscopy has opened the door to the study of novel ultracold atomic and plasma systems. In particular, the study of Rydberg atoms in strong magnetic fields, which has previously been restricted to optically accessible low azimuthal quantum numbers |m|, has been expanded to include high azimuthal quantum numbers |m| through new collisional and recombinative processes which can play a role in this regime. We describe our efforts to realize this new regime experimentally with a superconducting atom and plasma trap. In theoretical work, we have implemented an efficient method to calculate the spectra of Rydberg atoms in strong magnetic fields. We use adiabatic basis sets that reflect the disparate time scales of the electronic motion parallel and transverse to the magnetic field. We find that, with increasing absolute value of |m|, non-adiabatic corrections become negligible, the adiabatic basis states and their energies become exact solutions, and the level statistics evolve from a Wigner to a Possonian distribution of the nearest-neighbor energy separations. The analogy between the adiabatically separable regime of large |m| and the behavior of charged particles in Penning traps will be discussed.

  4. Atomization methods for forming magnet powders

    SciTech Connect

    Sellers, C.H.; Branagan, D.J.; Hyde, T.A.

    2000-02-08

    The invention encompasses methods of utilizing atomization, methods for forming magnet powders, methods for forming magnets, and methods for forming bonded magnets. The invention further encompasses methods for simulating atomization conditions. In one aspect, the invention includes an atomization method for forming a magnet powder comprising: (a) forming a melt comprising R{sub 2.1}Q{sub 13.9}B{sub 1}, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; (b) atomizing the melt to form generally spherical alloy powder granules having an internal structure comprising at least one of a substantially amorphous phase or a substantially nanocrystalline phase; and (c) heat treating the alloy powder to increase an energy product of the alloy powder; after the heat treatment, the alloy powder comprising an energy product of at least 10 MGOe. In another aspect, the invention includes a magnet comprising R, Q, B, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; the magnet comprising an internal structure comprising R{sub 2.1}Q{sub 13.9}B{sub 1}.

  5. Atomization methods for forming magnet powders

    DOEpatents

    Sellers, Charles H.; Branagan, Daniel J.; Hyde, Timothy A.

    2000-01-01

    The invention encompasses methods of utilizing atomization, methods for forming magnet powders, methods for forming magnets, and methods for forming bonded magnets. The invention further encompasses methods for simulating atomization conditions. In one aspect, the invention includes an atomization method for forming a magnet powder comprising: a) forming a melt comprising R.sub.2.1 Q.sub.13.9 B.sub.1, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; b) atomizing the melt to form generally spherical alloy powder granules having an internal structure comprising at least one of a substantially amorphous phase or a substantially nanocrystalline phase; and c) heat treating the alloy powder to increase an energy product of the alloy powder; after the heat treatment, the alloy powder comprising an energy product of at least 10 MGOe. In another aspect, the invention includes a magnet comprising R, Q, B, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; the magnet comprising an internal structure comprising R.sub.2.1 Q.sub.13.9 B.sub.1.

  6. Atomic Calculations and Laboratory Measurements Relevant to X-ray Warm Absorbers

    NASA Technical Reports Server (NTRS)

    Kallman, Tim; Bautista, M.; Palmeri, P.

    2007-01-01

    This viewgraph document reviews the atomic calculations and the measurements from the laboratory that are relevant to our understanding of X-Ray Warm Absorbers. Included is a brief discussion of the theoretical and the experimental tools. Also included is a discussion of the challenges, and calculations relevant to dielectronic recombination, photoionization cross sections, and collisional ionization. A review of the models is included, and the sequence that the models were applied.

  7. A new miniaturized atomic magnetic gradiometer

    NASA Astrophysics Data System (ADS)

    Sheng, Dong; Perry, Abigail; Krzyzewski, Sean; Geller, Shawn; Knappe, Svenja; Kitching, John

    2016-05-01

    We report the development of a new miniaturized magnetic gradiometer using alkali atoms. The gradiometer, with the length of 5 cm and cross section diameter of 11 mm, is made of two chip-scale atomic magnetometers placed on a printed optical bench with a defined separation. Both magnetometers work in the spin-exchange relaxation free regime, share the same beam for pumping and probing to reduce the common mode noises from the lasers, and atom temperature is independently controlled by heating beams at telecom wavelength. With 2 cm baseline, 1 mW pumping beam power, and less than 400 mW input heating beam power, we measure a noise level of 15 fT/ Hz1/2 from the subtraction of two magnetometer outputs, which corresponds to a gradient field sensitivity of 7.5 fT/ Hz1/2/cm. The maximum common mode magnetic field noise rejection is up to 1000 within the gradiometer bandwidth. This device is useful in many fields that require both sensitive gradient field information and high common mode noise cancellation. We are also developing a new hybrid system based on this device to improve its dynamical range.

  8. Tailoring the chiral magnetic interaction between two individual atoms

    PubMed Central

    Khajetoorians, A. A.; Steinbrecher, M.; Ternes, M.; Bouhassoune, M.; dos Santos Dias, M.; Lounis, S.; Wiebe, J.; Wiesendanger, R.

    2016-01-01

    Chiral magnets are a promising route towards dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii–Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron-mediated Dzyaloshinskii–Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunnelling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets. PMID:26902332

  9. Tailoring the chiral magnetic interaction between two individual atoms.

    PubMed

    Khajetoorians, A A; Steinbrecher, M; Ternes, M; Bouhassoune, M; dos Santos Dias, M; Lounis, S; Wiebe, J; Wiesendanger, R

    2016-01-01

    Chiral magnets are a promising route towards dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii-Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron-mediated Dzyaloshinskii-Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunnelling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets. PMID:26902332

  10. Tailoring the chiral magnetic interaction between two individual atoms

    NASA Astrophysics Data System (ADS)

    Khajetoorians, A. A.; Steinbrecher, M.; Ternes, M.; Bouhassoune, M.; Dos Santos Dias, M.; Lounis, S.; Wiebe, J.; Wiesendanger, R.

    2016-02-01

    Chiral magnets are a promising route towards dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii-Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron-mediated Dzyaloshinskii-Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunnelling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets.

  11. Hydrogen atom in intense magnetic field.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Kelly, D. C.

    1972-01-01

    The structure of a hydrogen atom situated in an intense magnetic field is investigaged. Three approaches are employed. An elementary Bohr picture establishes a crucial magnetic field strength, H sub a approximately equal to 5 x 10 to the 9th G. Fields in excess of H sub a are intense in that they are able to modify the characteristic atomic scales of length and binding energy. A second approach solves the Schrodinger equation by a combination of variational methods and perturbation theory. It yields analytic expressions for the wave functions and energy eigenvalues. A third approach determines the energy eigenvalues by reducing the Schrodinger equation to a one-dimensional wave equation, which is then solved numerically. Energy eigenvalues are tabulated for field strengths of 2 x 10 to the 10th G and 2 x 10 to the 12th G. It is found that at 2 x 10 to the 12th G the lowest energy eigenvalue is changed from -13.6 to about -180 eV in agreement with previous variational computations.

  12. Studies of Interstellar and Circumstellar Magnetic Field with Aligned Atoms

    NASA Astrophysics Data System (ADS)

    Lazarian, A.; Yan, H.

    2004-12-01

    Population of levels of the hyperfine and fine split ground state of an atom is affected by radiative transitions induced by anisotropic radiation flux. Such aligned atoms precess in the external magnetic field and this affects properties of polarized radiation arising from both scattering and absorption by atoms. As the result the degree of light polarization depends on the direction of the magnetic field. This provides a new tool for studies of astrophysical magnetic fields using optical and UV polarimetry. We provide calculations for several atoms and ions that can be used to study magnetic fields in interplanetary medium, interstellar medius, circumstellar regions and quasars.

  13. Average-atom model combined with the hypernetted chain approximation applied to warm dense matter.

    PubMed

    Hou, Yong; Bredow, Richard; Yuan, Jianmin; Redmer, Ronald

    2015-03-01

    We have combined the average-atom model with the hypernetted chain approximation (AAHNC) to describe the electronic and ionic structure in the warm dense matter regime. On the basis of the electronic and ionic structures, the x-ray Thomson scattering (XRTS) spectrum is calculated using the random-phase approximation. While the electronic structure is described within the average-atom model, the effects of other ions on the electronic structure are considered using an integral equation method of the theory of liquids, namely the hypernetted chain approximation. The ion-ion pair potential is calculated using the modified Gordon-Kim model based on the electronic density distribution. Finally, the electronic and ionic structures are determined self-consistently. The XRTS spectrum is calculated according to the Chihara formula, where the scattering contributions are divided into three components: elastic, bound-free, and free-free. Comparison of the present AAHNC results with other theoretical models and experimental data shows very good agreement. Thus the AAHNC model can give a reasonable description of the electronic and ionic structure in warm dense matter. PMID:25871231

  14. Observation of Magnetically Induced Trap Loss of Ultracold Thulium Atoms

    NASA Astrophysics Data System (ADS)

    Kalganova, E. S.; Vishnyakova, G. A.; Golovizin, A. A.; Tregubov, D. O.; Sukachev, D. D.; Akimov, A. V.; Kolachevsky, N. N.; Khabarova, K. Yu.; Sorokin, V. N.

    2015-09-01

    We report the observation of influence of homogeneous magnetic field on an optical lattice losses of ultracold thulium atoms. The atomic cloud temperature was T = 15 mK. The dependence of trap population on a value of magnetic field has a broad resonance in the low-field region with a center at B = 0.4 G. We also have measured a decrease of optical lattice lifetime in a presence of resonance magnetic field. The observed magnetically-induced trap losses are assumed to be Feshbach resonance which is a dependence of an atomic scattering length on magnetic field.

  15. Atomic-scale control of graphene magnetism by using hydrogen atoms

    NASA Astrophysics Data System (ADS)

    González-Herrero, Héctor; Gómez-Rodríguez, José M.; Mallet, Pierre; Moaied, Mohamed; Palacios, Juan José; Salgado, Carlos; Ugeda, Miguel M.; Veuillen, Jean-Yves; Yndurain, Félix; Brihuega, Iván

    2016-04-01

    Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate that the adsorption of a single hydrogen atom on graphene induces a magnetic moment characterized by a ~20–millielectron volt spin-split state at the Fermi energy. Our scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, show that such a spin-polarized state is essentially localized on the carbon sublattice opposite to the one where the hydrogen atom is chemisorbed. This atomically modulated spin texture, which extends several nanometers away from the hydrogen atom, drives the direct coupling between the magnetic moments at unusually long distances. By using the STM tip to manipulate hydrogen atoms with atomic precision, it is possible to tailor the magnetism of selected graphene regions.

  16. Atomic-scale control of graphene magnetism by using hydrogen atoms.

    PubMed

    González-Herrero, Héctor; Gómez-Rodríguez, José M; Mallet, Pierre; Moaied, Mohamed; Palacios, Juan José; Salgado, Carlos; Ugeda, Miguel M; Veuillen, Jean-Yves; Yndurain, Félix; Brihuega, Iván

    2016-04-22

    Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate that the adsorption of a single hydrogen atom on graphene induces a magnetic moment characterized by a ~20-millielectron volt spin-split state at the Fermi energy. Our scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, show that such a spin-polarized state is essentially localized on the carbon sublattice opposite to the one where the hydrogen atom is chemisorbed. This atomically modulated spin texture, which extends several nanometers away from the hydrogen atom, drives the direct coupling between the magnetic moments at unusually long distances. By using the STM tip to manipulate hydrogen atoms with atomic precision, it is possible to tailor the magnetism of selected graphene regions. PMID:27102478

  17. Magnetism and spin-polarized transport in carbon atomic wires

    NASA Astrophysics Data System (ADS)

    Li, Z. Y.; Sheng, W.; Ning, Z. Y.; Zhang, Z. H.; Yang, Z. Q.; Guo, H.

    2009-09-01

    We report ab initio calculations of magnetic and spin-polarized quantum transport properties of pure and nitrogen-doped carbon atomic wires. For finite-sized wires with even number of carbon atoms, total magnetic moment of 2μB is found. On the other hand, wires with odd number atoms have no net magnetic moment. Doped with one or two nitrogen atom(s), the carbon atomic wires exhibit a spin-density-wave-like state. The magnetic properties can be rationalized through bonding patterns and unpaired states. When the wire is sandwiched between Au electrodes to form a transport junction, perfect spin filtering effect can be induced by slightly straining the wire.

  18. Effect of Transverse Magnetic Fields on Cold-Atom Nonlinear Magneto-Optical Rotation

    NASA Astrophysics Data System (ADS)

    Meyer, David; Kunz, Paul; Fatemi, Fredrik; Quraishi, Qudsia

    2016-05-01

    We investigate nonlinear magneto-optical rotation (NMOR) in cold atoms in the presence of a transverse magnetic field where alignment-to-orientation conversion (AOC) dominates. The AOC mechanism, which relies on AC-Stark shifts generated by a strong, off-resonant probe beam, significantly alters the NMOR resonance. When an additional magnetic field is present, parallel to the electric field of the light, a nested feature within this NMOR resonance manifests. Unlike similar features observed with lower optical power in warm vapors, attributed to optical pumping through nearby hyperfine levels, this feature is due solely to the AOC mechanism. Using numerical simulations, a perturbative solution, and experimental observations we characterize the feature with respect to optical power, optical polarization, magnetic field strength, and magnetic field direction. These results shed further light on the AOC mechanism common to NMOR-based experiments and we demonstrate a potential application to measure transverse DC magnetic fields and spatial gradients.

  19. Angular Momentum of a Magnetically Trapped Atomic Condensate

    SciTech Connect

    Zhang, P.; Jen, H. H.; Sun, C. P.; You, L.

    2007-01-19

    For an atomic condensate in an axially symmetric magnetic trap, the sum of the axial components of the orbital angular momentum and the hyperfine spin is conserved. Inside an Ioffe-Pritchard trap (IPT) whose magnetic field (B field) is not axially symmetric, the difference of the two becomes surprisingly conserved. In this Letter we investigate the relationship between the values of the sum or difference angular momentums for an atomic condensate inside a magnetic trap and the associated gauge potential induced by the adiabatic approximation. Our result provides significant new insight into the vorticity of magnetically trapped atomic quantum gases.

  20. Dynamical Generation of Topological Magnetic Lattices for Ultracold Atoms.

    PubMed

    Yu, Jinlong; Xu, Zhi-Fang; Lü, Rong; You, Li

    2016-04-01

    We propose a scheme to dynamically synthesize a space-periodic effective magnetic field for neutral atoms by time-periodic magnetic field pulses. When atomic spin adiabatically follows the direction of the effective magnetic field, an adiabatic scalar potential together with a geometric vector potential emerges for the atomic center-of-mass motion, due to the Berry phase effect. While atoms hop between honeycomb lattice sites formed by the minima of the adiabatic potential, complex Peierls phase factors in the hopping coefficients are induced by the vector potential, and these phase factors facilitate a topological Chern insulator. With further tuning of external parameters, both a topological phase transition and topological flat bands can be achieved, highlighting realistic prospects for studying strongly correlated phenomena in this system. Our Letter presents an alternative pathway towards creating and manipulating topological states of ultracold atoms by magnetic fields. PMID:27104703

  1. Dynamical Generation of Topological Magnetic Lattices for Ultracold Atoms

    NASA Astrophysics Data System (ADS)

    Yu, Jinlong; Xu, Zhi-Fang; Lü, Rong; You, Li

    2016-04-01

    We propose a scheme to dynamically synthesize a space-periodic effective magnetic field for neutral atoms by time-periodic magnetic field pulses. When atomic spin adiabatically follows the direction of the effective magnetic field, an adiabatic scalar potential together with a geometric vector potential emerges for the atomic center-of-mass motion, due to the Berry phase effect. While atoms hop between honeycomb lattice sites formed by the minima of the adiabatic potential, complex Peierls phase factors in the hopping coefficients are induced by the vector potential, and these phase factors facilitate a topological Chern insulator. With further tuning of external parameters, both a topological phase transition and topological flat bands can be achieved, highlighting realistic prospects for studying strongly correlated phenomena in this system. Our Letter presents an alternative pathway towards creating and manipulating topological states of ultracold atoms by magnetic fields.

  2. Spin sensing and magnetic design at the single atom level

    NASA Astrophysics Data System (ADS)

    Khajetoorians, Alexander

    2015-03-01

    Unraveling many of the current dilemmas in nanoscience hinges on the advancement of techniques which can probe the spin degrees of freedom with high spatial, energy, and ultimately high temporal resolution. With the development of sub-Kelvin high-magnetic field STM, two complementary methods, namely spin-polarized scanning tunneling spectroscopy (SP-STS) and inelastic STS (ISTS), can address single spins at the atomic scale with unprecedented precession. While SP-STS reads out the projection of the impurity magnetization, ISTS detects the excitations of this magnetization as a function of an external magnetic field. They are thus the analogs of magnetometry and spin resonance measurements pushed to the single atom limit. I have recently demonstrated that it is possible to reliably combine single atom magnetometry with an atom-by-atom bottom-up fabrication to realize complex atomic-scale magnets with tailored properties on metallic surfaces. I will discuss the current state of the art of this growing field as it pertains to single spin information storage, and how the functionality of coupled magnetic adatoms can be tailored on surfaces. Finally, I will present an outlook on future perspectives in the field of single atom magnetism and the promising application of single spin detection to broader scopes in nanoscience as a whole.

  3. Manipulating Neutral Atoms in Chip-Based Magnetic Traps

    NASA Technical Reports Server (NTRS)

    Aveline, David; Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Yu, Nan; Kohel, James

    2009-01-01

    Several techniques for manipulating neutral atoms (more precisely, ultracold clouds of neutral atoms) in chip-based magnetic traps and atomic waveguides have been demonstrated. Such traps and waveguides are promising components of future quantum sensors that would offer sensitivities much greater than those of conventional sensors. Potential applications include gyroscopy and basic research in physical phenomena that involve gravitational and/or electromagnetic fields. The developed techniques make it possible to control atoms with greater versatility and dexterity than were previously possible and, hence, can be expected to contribute to the value of chip-based magnetic traps and atomic waveguides. The basic principle of these techniques is to control gradient magnetic fields with suitable timing so as to alter a trap to exert position-, velocity-, and/or time-dependent forces on atoms in the trap to obtain desired effects. The trap magnetic fields are generated by controlled electric currents flowing in both macroscopic off-chip electromagnet coils and microscopic wires on the surface of the chip. The methods are best explained in terms of examples. Rather than simply allowing atoms to expand freely into an atomic waveguide, one can give them a controllable push by switching on an externally generated or a chip-based gradient magnetic field. This push can increase the speed of the atoms, typically from about 5 to about 20 cm/s. Applying a non-linear magnetic-field gradient exerts different forces on atoms in different positions a phenomenon that one can exploit by introducing a delay between releasing atoms into the waveguide and turning on the magnetic field.

  4. Quantum molecular dynamics study of expanded beryllium: Evolution from warm dense matter to atomic fluid

    PubMed Central

    Li, Dafang; Liu, Haitao; Zeng, Siliang; Wang, Cong; Wu, Zeqing; Zhang, Ping; Yan, Jun

    2014-01-01

    By performing quantum molecular dynamics (QMD) simulations, we investigate the equation of states, electrical and optical properties of the expanded beryllium at densities two to one-hundred lower than the normal solid density, and temperatures ranging from 5000 to 30000 K. With decreasing the density of Be, the optical response evolves from the one characteristic of a simple metal to the one of an atomic fluid. By fitting the optical conductivity spectra with the Drude-Smith model, it is found that the conducting electrons become localized at lower densities. In addition, the negative derivative of the electrical resistivity on temperature at density about eight lower than the normal solid density demonstrates that the metal to nonmetal transition takes place in the expanded Be. To interpret this transition, the electronic density of states is analyzed systematically. Furthermore, a direct comparison of the Rosseland opacity obtained by using QMD and the standard opacity code demonstrates that QMD provides a powerful tool to validate plasma models used in atomic physics approaches in the warm dense matter regime. PMID:25081816

  5. Induce magnetism into silicene by embedding transition-metal atoms

    SciTech Connect

    Sun, Xiaotian; Wang, Lu E-mail: yyli@suda.edu.cn; Lin, Haiping; Hou, Tingjun; Li, Youyong E-mail: yyli@suda.edu.cn

    2015-06-01

    Embedding transition-metal (TM) atoms into nonmagnetic nanomaterials is an efficient way to induce magnetism. Using first-principles calculations, we systematically investigated the structural stability and magnetic properties of TM atoms from Sc to Zn embedded into silicene with single vacancy (SV) and double vacancies (DV). The binding energies for different TM atoms correlate with the TM d-shell electrons. Sc, Ti, and Co show the largest binding energies of as high as 6 eV, while Zn has the lowest binding energy of about 2 eV. The magnetic moment of silicene can be modulated by embedding TM atoms from V to Co, which mainly comes from the 3d orbitals of TM along with partly contributions from the neighboring Si atoms. Fe atom on SV and Mn atom on DV have the largest magnetic moment of more than 3 μB. In addition, we find that doping of N or C atoms on the vacancy site could greatly enhance the magnetism of the systems. Our results provide a promising approach to design silicene-based nanoelectronics and spintronics device.

  6. Tailoring the chiral magnetic interaction between two individual atoms

    NASA Astrophysics Data System (ADS)

    Wiebe, J.; Khajetoorians, A. A.; Steinbrecher, M.; Ternes, M.; Bouhassoune, M.; Dos Santos Dias, M.; Lounis, S.; Wiesendanger, R.

    Chiral magnets are a promising route toward dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii-Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron mediated Dzyaloshinskii-Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunneling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets. Acknowledgements: SFB668, GrK1286, SFB767, LO 1659 5-1, Emmy Noether Program of the DFG, FOM of NWO, VH-NG-717.

  7. Detection of brain magnetic fields with an atomic magnetometer

    NASA Astrophysics Data System (ADS)

    Xia, Hui; Hoffman, Dan; Baranga, Andrei; Romalis, Michael

    2006-05-01

    We report detection of magnetic fields generated by evoked brain activity with an atomic magnetometer. The measurements are performed with a high-density potassium magnetometer operating in a spin-exchange relaxation free regime. Compared to SQUID magnetometers which so far have been the only detectors capable of measuring the magnetic fields from the brain, atomic magnetometers have the advantages of higher sensitivity and spatial resolution, simple multi-channel recording, and no need for cryogenics. Using a multi-channel photodetector array we recorded magnetic fields from the brain correlated with an audio tone administered with a non-magnetic earphone. The spatial map of the magnetic field gives information about the location of the brain region responding to the auditory stimulation. Our results demonstrate the atomic magnetometer as an alternative and low cost technique for brain imaging applications, without using cryogenic apparatus.

  8. Improved trapping and transport of cold atoms for magnetic microscopy

    NASA Astrophysics Data System (ADS)

    Gadge, Amruta; James, T.; Li, X.; Lu, Bo; Garridogonzalez, N.; Finke, A.; Mellor, C.; Fromhold, M.; Koller, C.; Orucevic, F.; Kruger, Peter

    2016-05-01

    Using cold atoms, a very sensitive and high resolution magnetic and electric field sensor can be realised. Ultra-close trapping of atoms would improve the resolution of cold-atom based surface probes. The limitation on the trapping distance arises from strongly distance-dependent effects such as Casimir force, Johnson noise etc. We are constructing an experimental system to trap atoms at surface separations of less than a micron. We will demonstrate the possibility of using special surfaces such as silicon nitride membranes and graphene for sub-micron trapping. We have designed a 10-layer printed circuit board, which can magnetically trap the cold atom cloud and transport it precisely to a desired location. This gives us the ability to study multiple samples within the same vacuum environment. In order to achieve higher atom number in the initial trapping stages, we use a dual-color MOT technique for Rb-87 atoms. Using this technique we achieve a significant increase in atom number and decrease in temperature. In this talk, I will present the results of the dual color MOT. I will also report on results related to magnetic transport and sub-micron trapping of atoms.

  9. Single-impulse magnetic focusing of launched cold atoms

    NASA Astrophysics Data System (ADS)

    Pritchard, Matthew J.; Arnold, Aidan S.; Smith, David A.; Hughes, Ifan G.

    2004-11-01

    We have theoretically investigated the focusing of a launched cloud of cold atoms. Time-dependent spatially-varying magnetic fields are used to impart impulses leading to a three-dimensional focus of the launched cloud. We discuss possible coil arrangements for a new focusing regime: isotropic 3D focusing of atoms with a single-impulse magnetic lens. We investigate focusing aberrations and find that, for typical experimental parameters, the widely used assumption of a purely harmonic lens is often inaccurate. The baseball lens offers the best possibility for isotropically focusing a cloud of weak-field-seeking atoms in 3D.

  10. Quantum magnetism of alkali Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Malinovskaya, Svetlana; Liu, Gengyuan

    2016-05-01

    We discuss a method to control dynamics in many-body spin states of 87Rb Rydberg atoms. The method permits excitation of cold gases and form ordered structures of alkali atoms. It makes use of a two-photon excitation scheme with circularly polarized and linearly chirped pulses. The method aims for controlled quantum state preparation in large ensembles. It is actual for experiments studding the spin hopping dynamics and realization of quantum random walks.

  11. Detecting magnetic ordering with atomic size electron probes

    DOE PAGESBeta

    Idrobo, Juan Carlos; Rusz, Ján; Spiegelberg, Jakob; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Cantoni, Claudia; Lupini, Andrew R.

    2016-05-27

    While magnetism originates at the atomic scale, the existing spectroscopic techniques sensitive to magnetic signals only produce spectra with spatial resolution on a larger scale. However, recently, it has been theoretically argued that atomic size electron probes with customized phase distributions can detect magnetic circular dichroism. Here, we report a direct experimental real-space detection of magnetic circular dichroism in aberration-corrected scanning transmission electron microscopy (STEM). Using an atomic size-aberrated electron probe with a customized phase distribution, we reveal the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The novel experimental setupmore » presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution.« less

  12. Emerging magnetic order in platinum atomic contacts and chains

    PubMed Central

    Strigl, Florian; Espy, Christopher; Bückle, Maximilian; Scheer, Elke; Pietsch, Torsten

    2015-01-01

    The development of atomic-scale structures revealing novel transport phenomena is a major goal of nanotechnology. Examples include chains of atoms that form while stretching a transition metal contact or the predicted formation of magnetic order in these chains, the existence of which is still debated. Here we report an experimental study of the magneto-conductance (MC) and anisotropic MC with atomic-size contacts and mono-atomic chains of the nonmagnetic metal platinum. We find a pronounced and diverse MC behaviour, the amplitude and functional dependence change when stretching the contact by subatomic distances. These findings can be interpreted as a signature of local magnetic order in the chain, which may be of particular importance for the application of atomic-sized contacts in spintronic devices of the smallest possible size. PMID:25649440

  13. Atomic micromotion and geometric forces in a triaxial magnetic trap

    PubMed

    Muller; Morsch; Ciampini; Anderlini; Mannella; Arimondo

    2000-11-20

    Nonadiabatic motion of Bose-Einstein condensates of rubidium atoms arising from the dynamical nature of a time-orbiting-potential (TOP) trap was observed experimentally. The orbital micromotion of the condensate in velocity space at the frequency of the rotating bias field of the TOP was detected by a time-of-flight method. A dependence of the equilibrium position of the atoms on the sense of rotation of the bias field was observed. We have compared our experimental findings with numerical simulations. The nonadiabatic following of the atomic spin in the trap rotating magnetic field produces geometric forces acting on the trapped atoms. PMID:11082569

  14. Magnetism and surface structure of atomically controlled ultrathin metal films.

    SciTech Connect

    Shiratsuchi, Yu.; Yamamoto, M.; Bader, S. D.; Materials Science Division; Osaka Univ.

    2007-01-01

    We review the correlation of magnetism and surface structure in ultrathin metal films, including the tailoring of novel magnetic properties using atomic scale control of the nanostructure. We provide an overview of modern fabrication and characterization techniques used to create and explore these fascinating materials, and highlight important phenomena of interest. We also discuss techniques that control and characterize both the magnetic and structural properties on an atomic scale. Recent advances in the development and applications of these techniques allow nanomagnetism to be investigated in an unprecedented manner. A system cannot necessarily retain a two-dimensional structure as it enters the ultrathin region, but it can transform into a three-dimensional, discontinuous structure due to the Volmer-Weber growth mechanism. This structural transformation can give rise to superparamagnetism. During this evolution, competing factors such as interparticle interactions and the effective magnetic anisotropy govern the magnetic state. These magnetic parameters are influenced by the nanostructure of the film. In particular, controlling the magnetic anisotropy is critical for determining the magnetic properties. Surface effects play especially important roles in influencing both the magnitude and direction of the magnetic anisotropy in ultrathin films. By properly altering the surface structure, the strength and direction of the magnetic anisotropy are controlled via spin-orbit and/or dipole interactions.

  15. Magnetohydrodynamic Simulations of Disk GalaxyFormation: the Magnetization of The Cold and Warm Medium

    SciTech Connect

    Wang, Peng; Abel, Tom; /KIPAC, Menlo Park /Santa Barbara, KITP

    2007-12-18

    Using magnetohydrodynamic (MHD) adaptive mesh refinement simulations, we study the formation and early evolution of disk galaxies with a magnetized interstellar medium. For a 10{sup 10} M{sub {circle_dot}} halo with initial NFW dark matter and gas profiles, we impose a uniform 10{sup -9} G magnetic field and follow its collapse, disk formation and evolution up to 1 Gyr. Comparing to a purely hydrodynamic simulation with the same initial condition, we find that a protogalactic field of this strength does not significantly influence the global disk properties. At the same time, the initial magnetic fields are quickly amplified by the differentially rotating turbulent disk. After the initial rapid amplification lasting {approx} 500 Myr, subsequent field amplification appears self-regulated. As a result, highly magnetized material begin to form above and below the disk. Interestingly, the field strengths in the self-regulated regime agrees well with the observed fields in the Milky Way galaxy both in the warm and the cold HI phase and do not change appreciably with time. Most of the cold phase shows a dispersion of order ten in the magnetic field strength. The global azimuthal magnetic fields reverse at different radii and the amplitude declines as a function of radius of the disk. By comparing the estimated star formation rate (SFR) in hydrodynamic and MHD simulations, we find that after the magnetic field strength saturates, magnetic forces provide further support in the cold gas and lead to a decline of the SFR.

  16. Neutral Atom Nanolithography Using a Pulsed Magnetic Lens

    NASA Astrophysics Data System (ADS)

    Anciaux, Erik; Castillo-Garza, Rodrigo; Gardner, Jamie; Raizen, Mark

    2015-03-01

    We present the status of a method of neutral atom lithography that achieves sub-10nm resolution. This method is based on the nanoscale imaging of a beam of metastable atoms with an aberration-corrected hexapole lens. The lens creates a magnetic field gradient that increases with the distance from the center of the lens so as to focus divergent low field seeking atoms toward a single focal spot past the lens. The scheme takes advantage of the narrow velocity distribution of a pulsed supersonic beam as well as an optical pumping and cooling scheme that selects the magnetic state of the atoms and further reduces its velocity dispersion. This method can be used not only to pattern but to spectroscopically probe surfaces with spatial resolution below 10nm. . M. G. R. acknowledges support from the U.S. National Science Foundation, the R. A. Welch Foundation (Grant F-1258), and the Sid W. Richardson Foundation.

  17. Hexapole magnet system for thermal energy 3He atom manipulation

    NASA Astrophysics Data System (ADS)

    Jardine, A. P.; Fouquet, P.; Ellis, J.; Allison, W.

    2001-10-01

    We present design and construction details for a novel high field, small bore permanent hexapole magnet. The design is intended for focusing atomic beams of 3He at thermal energies. The magnet uses an optimized polepiece design which includes vacuum gaps to enable its use with high intensity atomic and molecular beams. The 0.3 m long, 1 mm internal radius magnet achieves a polepiece tip field of 1.1 T using NdFeB permanent magnets and Permendur 49 polepieces. The polepiece shanks are designed to saturate so that the hexapole properties are determined predominantly by the shape of the polepiece tip. The performance of the hexapole assembly is demonstrated with an 8 meV 3He beam in the beam source of the Cambridge spin echo spectrometer and the measured focused beam results show excellent agreement with theoretical predictions and negligible beam attenuation.

  18. Permanent magnetic lattices for ultracold atoms and quantum degenerate gases

    NASA Astrophysics Data System (ADS)

    Ghanbari, Saeed; Kieu, Tien D.; Sidorov, Andrei; Hannaford, Peter

    2006-02-01

    We propose the use of periodic arrays of permanent magnetic films for producing magnetic lattices of microtraps for confining, manipulating and controlling small clouds of ultracold atoms and quantum degenerate gases. Using analytical expressions and numerical calculations we show that periodic arrays of magnetic films can produce one-dimensional (1D) and two-dimensional (2D) magnetic lattices with non-zero potential minima, allowing ultracold atoms to be trapped without losses due to spin flips. In particular, we show that two crossed layers of periodic arrays of parallel rectangular magnets plus bias fields, or a single layer of periodic arrays of square-shaped magnets with three different thicknesses plus bias fields, can produce 2D magnetic lattices of microtraps having non-zero potential minima and controllable trap depth. For arrays with micron-scale periodicity, the magnetic microtraps can have very large trap depths (~0.5 mK for the realistic parameters chosen for the 2D lattice) and very tight confinement.

  19. Enhanced Magnetic Trap Loading for Alkaline-Earth Atoms

    NASA Astrophysics Data System (ADS)

    Reschovsky, Benjamin J.; Barker, Daniel S.; Pisenti, Neal C.; Campbell, Gretchen K.

    2016-05-01

    We report on a technique to improve the continuous loading of atomic strontium into a magnetic trap from a Magneto-Optical Trap (MOT). This is achieved by adding a depumping laser addressing the 3P1 level. For the 3P1 -->3S1 (688-nm) transition in strontium, the depumping laser increases atom number in the magnetic trap and subsequent cooling stages by up to 65 % for the bosonic isotopes and up to 30 % for the fermionic isotope. We optimize this trap loading strategy with respect to the 688-nm laser detuning, intensity, and beam size. To understand the results, we develop a one-dimensional rate equation model of the system, which is in good agreement with the data. We discuss the use of other transitions in strontium for accelerated trap loading and the application of the technique to other alkaline-earth-like atoms.

  20. A Warm Bore Anticryostat for Series Magnetic Measurements of LHC Superconducting Dipole and Short-Straight-Section Magnets

    NASA Astrophysics Data System (ADS)

    Dunkel, O.; Legrand, P.; Sievers, P.

    2004-06-01

    All LHC twin aperture magnets will be tested under operating conditions to verify their performance. The field measurement equipment works at ambient temperature and pressure. Each magnet is therefore equipped with two warm bore anticryostats. As a consequence a total of nearly 80 anticryostats of different lengths have to be assembled, handled and serviced during the test period. Two main constraints determine the frame for the design of these anticryostats: inside a given beam pipe aperture of 50 mm kept at 1.9 K, a warm bore aperture of 40 mm must provide the highest possible mechanical stability and robustness for numerous mounting cycles as well as the lowest possible heat losses towards the cryogenic system. In addition, compatibility with high magnetic fields and an insulation vacuum of about 10-7 mbar have to be maintained. This paper describes how a satisfactory mechanical stability as well as heat losses in the order of 0.8 W/m are achieved with a design based on very careful space and material optimization. Other aspects like assembly, installation, thermal behavior and temperature control during the operation are described.

  1. Magnetic shielding of the cold atom space clock PHARAO

    NASA Astrophysics Data System (ADS)

    Moric, Igor; Laurent, Philippe; Chatard, Philippe; de Graeve, Charles-Marie; Thomin, Stephane; Christophe, Vincent; Grosjean, Olivier

    2014-09-01

    The space clock PHARAO is an atomic clock based on laser cooled cesium atoms. In order to attenuate magnetic field fluctuation in orbit, PHARAO clock uses three concentric Mumetal magnetic shields combined with several coils to improve the field homogeneity. We have characterized the attenuation and magnetic field homogeneity of the shields used to build the flight model. The average value of attenuation inside the three shields is around 18,000 when the external field is similar to the orbit field (30 μT) and the field homogeneity is lower than 10 nT. These values have not changed after vibrations and thermal tests for the space qualification. Permeability variation of the shields as a function of the intercepted flux has been analyzed.

  2. Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter

    NASA Astrophysics Data System (ADS)

    Johnson, W. R.; Nilsen, J.

    2016-03-01

    The influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity and also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.

  3. Spin nutation induced by atomic motion in a magnetic lattice

    SciTech Connect

    Kobayashi, Y.; Shiraishi, Y.; Hatakeyama, A.

    2010-12-15

    An atom moving in a spatially periodic field experiences a temporally periodic perturbation and undergoes a resonance transition between atomic internal states when the transition frequency is equal to the atomic velocity divided by the field period. We demonstrated that spin nutation was induced by this resonant transition in a polarized rubidium (Rb) atomic beam passing through a magnetic lattice. The lattice was produced by current flowing through an array of parallel wires crossing the beam. This array structure, reminiscent of a multiwire chamber for particle detection, allowed the Rb beam to pass through the lattice at a variety of incident angles. The dephasing of spin nutation was reduced by varying the incident angle.

  4. Magnetic-field-assisted atomic polarization spectroscopy of 4 He

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Wang, Haidong; Wu, Teng; Peng, Xiang; Guo, Hong; Cream Team

    2016-05-01

    Atomic polarization spectroscopy (PS) is a high resolution sub-Doppler atomic spectroscopic technique with free modulation. It is always desirable to obtain a PS signal with zero background as it can provide a more preferable laser frequency stabilization performance. There are many factors that can affect the PS signal background, i.e., the laser power, the laser polarization and the magnetic field. Here, we demonstrate a method for observing and analyzing the effects on the PS signal of 4 He under different magnetic fields. At the beginning, under nearly zero magnetic field, the large asymmetrical PS signal background has been observed and cannot be eliminated by only optically adjusting. Then, we find that the PS signal profile can be changed and controlled by varying the magnetic field with transverse or longitudinal direction and different intensity. The optimized PS signal with symmetrical dispersive profile and zero background is obtained when the magnetic field is chosen and controlled in the transverse direction and more than 20000nT intensity. Similar phenomenon cannot be observed under the longitudinal magnetic field. A theoretical model is also presented, which explains and agrees well with our experimental results.

  5. Dynamics of neutral atoms in artificial magnetic field

    NASA Astrophysics Data System (ADS)

    Yu, Zi-Fa; Hu, Fang-Qi; Zhang, Ai-Xia; Xue, Ju-Kui

    2016-02-01

    Cyclotron dynamics of neutral atoms in a harmonic trap potential with artificial magnetic field is studied theoretically. The cyclotron orbit is obtained analytically and confirmed numerically. When the external harmonic potential is absent, artificial magnetic field can result in the singly periodic circular motion of Bose gas with the emergence of a Lorentz-like force, which is similar to particles with electric charge moving in a magnetic field. However, the coupling between artificial magnetic field and harmonic trap potential leads to rich and complex cyclotron trajectory, which depends on √{B2 + 1 }, where B is the rescaled artificial magnetic field. When √{B2 + 1 } is a rational number, the cyclotron orbit is multiply periodic and closed. However, when √{B2 + 1 } is an irrational number, the cyclotron orbit is quasiperiodic, i.e., the cyclotron motion of Bose gas is limited in a annular region, and eventually, the motion is ergodic in this region. Furthermore, the cyclotron orbits also depend on the initial conditions of Bose gas. Thus, the cyclotron dynamics of Bose gas can be manipulated in a controllable way by changing the artificial magnetic field, harmonic trap potential and initial conditions. Our results provide a direct theoretical evidence for the cyclotron dynamics of neutral atoms in the artificial gauge field.

  6. Influence of noise on a magnetically sensitive atom interferometer

    NASA Astrophysics Data System (ADS)

    Desavage, Sara A.; Srinivasan, Arvind; Davis, Jon P.; Zimmermann, Matthias; Efremov, Maxim; Rasel, Ernst; Schleich, Wolfgang; Welch, George R.; Mimih, Jihane; Narducci, Frank A.

    2016-05-01

    The inherent sensitivity of atom interferometer sensors has been well established and much progress has been made in the development of atom interferometer gravimeters, gravity gradiometers and gyroscopes e.g.. These interferometers use the ``clock'' transition which is magnetically insensitive. When considering interferometers with magnetically sensitive transitions operating in unshielded environments additional noise sources must be considered. The frequency content of the noise from these sources can vary dramatically, depending on the environment. In this talk, we will discuss these various noise sources and their impact on the performance of magnetically sensitive interferometers. Specifically, we identify three ways by which noise can be introduced into the system and their effect: fluctuating detuning, leading to a randomness of the interference pattern; fluctuating Rabi frequency, leading to pulse errors; non-uniformity of the magnetic field across the atom cloud, which can, under certain circumstances lead to a complete washing out of the interference pattern. Implications for our current experiments will be discussed. Sponsored by the Office of Naval Research.

  7. Ultrasensitive magnetic field detection using a single artificial atom.

    PubMed

    Bal, M; Deng, C; Orgiazzi, J-L; Ong, F R; Lupascu, A

    2012-01-01

    Efficient detection of magnetic fields is central to many areas of research and technology. High-sensitivity detectors are commonly built using direct-current superconducting quantum interference devices or atomic systems. Here we use a single artificial atom to implement an ultrasensitive magnetometer with micron range size. The artificial atom, a superconducting two-level system, is operated similarly to atom and diamond nitrogen-vacancy centre-based magnetometers. The high sensitivity results from quantum coherence combined with strong coupling to magnetic field. We obtain a sensitivity of 3.3 pT Hz(-1/2) for a frequency at 10 MHz. We discuss feasible improvements to increase sensitivity by one order of magnitude. The intrinsic sensitivity of this detector at frequencies in the 100 kHz-10 MHz range compares favourably with direct-current superconducting quantum interference devices and atomic magnetometers of equivalent spatial resolution. This result illustrates the potential of artificial quantum systems for sensitive detection and related applications. PMID:23271657

  8. Atomically thin dilute magnetism in Co-doped phosphorene

    NASA Astrophysics Data System (ADS)

    Seixas, L.; Carvalho, A.; Castro Neto, A. H.

    2015-04-01

    Two-dimensional dilute magnetic semiconductors can provide fundamental insights into the very nature of magnetic order and their manipulation through electron and hole doping. Besides the fundamental interest, due to the possibility of control of charge density, they can be extremely important in spintronics applications such as spin valve and spin-based transistors. In this paper, we studied a two-dimensional dilute magnetic semiconductor consisting of a phosphorene monolayer doped with cobalt atoms in substitutional and interstitial defects. We show that these defects can be stabilized and are electrically active. Furthermore, by including holes or electrons by a potential gate, the exchange interaction and magnetic order can be engineered, and may even induce a ferromagnetic-to-antiferromagnetic phase transition in p -doped phosphorene. At a Co concentration of 2.7%, we estimate a Curie temperature of TCMF A=466 K in the mean-field approximation.

  9. Reinventing atomic magnetic simulations with spin-orbit coupling

    DOE PAGESBeta

    Perera, Meewanage Dilina N.; Eisenbach, Markus; Nicholson, Don M.; Stocks, George Malcolm; Landau, David P.

    2016-02-10

    We propose a powerful extension to the combined molecular and spin dynamics method that fully captures the coupling between the atomic and spin subsystems via spin-orbit interactions. Moreover, the foundation of this method lies in the inclusion of the local magnetic anisotropies that arise as a consequence of the lattice symmetry breaking due to phonons or crystallographic defects. By using canonical simulations of bcc iron with the system coupled to a phonon heat bath, we show that our extension enables the previously unachievable angular momentum exchange between the atomic and spin degrees of freedom.

  10. Environmental magnetic evidence for a dynamic Taylor Glacier during the mid-Pliocene warm period

    NASA Astrophysics Data System (ADS)

    Ohneiser, Christian; Wilson, Gary; Florindo, Fabio

    2010-05-01

    of McMurdo Volcanic material to the signal. At ~200 meters in DVDP-11 and ~155 m in DVDP-10 a major mid-Pliocene hiatus truncates a ~40 meter thick interval (Interval II) of muds and diamicts which represents the mid-Pliocene warm period. Magnetically, this interval is unique within the cores because it has relatively low concentrations of magnetite and an upward fining of the magnetic grainsize. We suggest that this interval represents a retreated Taylor Glacier system under warm conditions followed by a re-advance under cooler conditions. The glacial advance immediately prior to the unconformity is marked by increasing magnetite concentration in parallel with decreasing magnetic grain size. The unconformity itself marks a switch from Taylor Valley or EAIS-derived sediments below to Ross Sea Ice or WAIS-derived sediments above. Below Interval II and to the base of each core are mid-Pliocene to latest Miocene Taylor Valley derived diamicts. Magnetic grainsizes and concentrations are variable over this interval indicating a dynamic Taylor Glacier which underwent multiple advances and retreats. Efforts are underway to correlate the magnetic properties of these cores with comparable interval in the ANDRILL MIS and SMS cores in order to build a more comprehensive regional understanding of this period.

  11. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    SciTech Connect

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-07

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 {mu}{Omega} cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  12. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    NASA Astrophysics Data System (ADS)

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-01

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 μΩ cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  13. Atomic magnetometer-based ultra-sensitive magnetic microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Young Jin; Savukov, Igor

    2016-03-01

    An atomic magnetometer (AM) based on lasers and alkali-metal vapor cells is currently the most sensitive non-cryogenic magnetic-field sensor. Many applications in neuroscience and other fields require high resolution, high sensitivity magnetic microscopic measurements. In order to meet this need we combined a cm-size spin-exchange relaxation-free AM with a flux guide (FG) to produce an ultra-sensitive FG-AM magnetic microscope. The FG serves to transmit the target magnetic flux to the AM thus enhancing both the sensitivity and resolution for tiny magnetic objects. In this talk, we will describe a prototype FG-AM device and present experimental and numerical tests of its sensitivity and resolution. We also demonstrate that an optimized FG-AM achieves high resolution and high sensitivity sufficient to detect a magnetic field of a single neuron in a few seconds, which would be an important milestone in neuroscience. We anticipate that this unique device can be applied to the detection of a single neuron, the detection of magnetic nano-particles, which in turn are very important for detection of target molecules in national security and medical diagnostics, and non-destructive testing.

  14. Optical atomic magnetometry for magnetic induction tomography of the heart

    NASA Astrophysics Data System (ADS)

    Deans, Cameron; Marmugi, Luca; Hussain, Sarah; Renzoni, Ferruccio

    2016-04-01

    We report on the use of radio-frequency optical atomic magnetometers for magnetic induction tomography measurements. We demonstrate the imaging of dummy targets of varying conductivities placed in the proximity of the sensor, in an unshielded environment at room-temperature and without background subtraction. The images produced by the system accurately reproduce the characteristics of the actual objects. Furthermore, we perform finite element simulations in order to assess the potential for measuring low-conductivity biological tissues with our system. Our results demonstrate the feasibility of an instrument based on optical atomic magnetometers for magnetic induction tomography imaging of biological samples, in particular for mapping anomalous conductivity in the heart.

  15. Designing Frustrated Quantum Magnets with Laser-Dressed Rydberg Atoms

    NASA Astrophysics Data System (ADS)

    Glaetzle, Alexander W.; Dalmonte, Marcello; Nath, Rejish; Gross, Christian; Bloch, Immanuel; Zoller, Peter

    2015-05-01

    We show how a broad class of lattice spin-1 /2 models with angular- and distance-dependent couplings can be realized with cold alkali atoms stored in optical or magnetic trap arrays. The effective spin-1 /2 is represented by a pair of atomic ground states, and spin-spin interactions are obtained by admixing van der Waals interactions between fine-structure split Rydberg states with laser light. The strengths of the diagonal spin interactions as well as the "flip-flop," and "flip-flip" and "flop-flop" interactions can be tuned by exploiting quantum interference, thus realizing different spin symmetries. The resulting energy scales of interactions compare well with typical temperatures and decoherence time scales, making the exploration of exotic forms of quantum magnetism, including emergent gauge theories and compass models, accessible within state-of-the-art experiments.

  16. Designing frustrated quantum magnets with laser-dressed Rydberg atoms.

    PubMed

    Glaetzle, Alexander W; Dalmonte, Marcello; Nath, Rejish; Gross, Christian; Bloch, Immanuel; Zoller, Peter

    2015-05-01

    We show how a broad class of lattice spin-1/2 models with angular- and distance-dependent couplings can be realized with cold alkali atoms stored in optical or magnetic trap arrays. The effective spin-1/2 is represented by a pair of atomic ground states, and spin-spin interactions are obtained by admixing van der Waals interactions between fine-structure split Rydberg states with laser light. The strengths of the diagonal spin interactions as well as the "flip-flop," and "flip-flip" and "flop-flop" interactions can be tuned by exploiting quantum interference, thus realizing different spin symmetries. The resulting energy scales of interactions compare well with typical temperatures and decoherence time scales, making the exploration of exotic forms of quantum magnetism, including emergent gauge theories and compass models, accessible within state-of-the-art experiments. PMID:25978228

  17. Helium atoms and molecules in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Mori, K.

    Recent theoretical studies have shown that the neutron star surface may be composed of helium or heavier elements as hydrogen may be quickly depleted by diffuse nuclear burning Chang Bildsten However while Hydrogen atmospheres have been studied in great details atomic data for helium is available only for He ion Pavlov Bezchastnov 2005 We performed Hartree-Fock type calculation for Helium atom and molecules and computed their binding ionization and dissociation energies in strong magnetic fields B sim10 12 -- 10 15 G We will present ionization balance of Helium atmospheres at typical magnetic field strengths and temperatures to radio-quiet neutron stars and AXPs We will also discuss several implications of helium atmosphere to X-ray data of isolated neutron stars focusing on the detected spectral features

  18. Atomic magnetic gradiometer for room temperature high sensitivity magnetic field detection

    DOEpatents

    Xu,Shoujun; Lowery, Thomas L.; Budker, Dmitry; Yashchuk, Valeriy V.; Wemmer, David E.; Pines, Alexander

    2009-08-11

    A laser-based atomic magnetometer (LBAM) apparatus measures magnetic fields, comprising: a plurality of polarization detector cells to detect magnetic fields; a laser source optically coupled to the polarization detector cells; and a signal detector that measures the laser source after being coupled to the polarization detector cells, which may be alkali cells. A single polarization cell may be used for nuclear magnetic resonance (NMR) by prepolarizing the nuclear spins of an analyte, encoding spectroscopic and/or spatial information, and detecting NMR signals from the analyte with a laser-based atomic magnetometer to form NMR spectra and/or magnetic resonance images (MRI). There is no need of a magnetic field or cryogenics in the detection step, as it is detected through the LBAM.

  19. Understanding atomic disorder in polar and magnetic oxides

    NASA Astrophysics Data System (ADS)

    Shoemaker, Daniel P.

    The functional properties of materials rely upon the composition, coordination, and connectivity of their constituent atoms. Understanding the atomic structure of condensed materials permits an understanding of how that structure influences macroscopic properties. The field of crystallography seeks to define the repeating lattice of periodic materials using a unit cell model with the minimum number of specified atomic positions. For magnetic and electronic materials, the arrangement of atoms and dipoles are often both ordered over long ranges and amenable to a traditional crystallographic description. However, interesting phenomena emerge when materials experience disorder due to chemical substitution, phase competition, nanostructuring, interfaces, or valence disproportionation. In those cases, the long-range symmetry of the material is interrupted and traditional crystallographic methods struggle to incorporate disorder into the unit cell model. I will discuss how disorder can be identified and quantified in functional materials. Each study includes examination of the real-space pair distribution function (PDF), which provides a weighted histogram of all atom-atom distances in a sample. Models are created by simultaneous fits to the Bragg profile and the PDF, thereby constraining the atomic positions by reciprocal- and real-space scattering descriptions. The reverse Monte Carlo method drives stochastic fits to scattering data using tens of thousands of atoms. Once simulation is complete, crystallographic metrics can be extracted from the supercell in real space. This approach is discussed in the case of site mixing and valence disproportionation in the Jahn-Teller active spinel CuMn2O4, local Jahn-Teller distortions of CuO4 tetrahedra in the solid solution Mg 1-xCuxCr 2O4, nanoscale phase co-existence at the metal-insulator transition in VO2, and static displacements and lone-pair activity in the pyrochlores Bi2Ti2O6O' and Bi 2Ru2O6O'.

  20. Atom interferometry in space: Thermal management and magnetic shielding

    SciTech Connect

    Milke, Alexander; Kubelka-Lange, André; Gürlebeck, Norman Rievers, Benny; Herrmann, Sven; Schuldt, Thilo; Braxmaier, Claus

    2014-08-15

    Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6 × 10{sup −4} % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 10{sup 5}. We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space.

  1. Atom interferometry in space: thermal management and magnetic shielding.

    PubMed

    Milke, Alexander; Kubelka-Lange, André; Gürlebeck, Norman; Rievers, Benny; Herrmann, Sven; Schuldt, Thilo; Braxmaier, Claus

    2014-08-01

    Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6 × 10(-4) % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 10(5). We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space. PMID:25173244

  2. Atom interferometry in space: Thermal management and magnetic shielding

    NASA Astrophysics Data System (ADS)

    Milke, Alexander; Kubelka-Lange, André; Gürlebeck, Norman; Rievers, Benny; Herrmann, Sven; Schuldt, Thilo; Braxmaier, Claus

    2014-08-01

    Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6 × 10-4 % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 105. We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space.

  3. Atomic spin chains as testing ground for quantum magnetism

    NASA Astrophysics Data System (ADS)

    Otte, Sander

    2015-03-01

    The field of quantum magnetism aims to capture the rich emergent physics that arises when multiple spins interact, in terms of elementary models such as the spin 1/2 Heisenberg chain. Experimental platforms to verify these models are rare and generally do not provide the possibility to detect spin correlations locally. In my lab we use low-temperature scanning tunneling microscopy to design and build artificial spin lattices with atomic precision. Inelastic electron tunneling spectroscopy enables us to identify the ground state and probe spin excitations as a function of system size, location inside the lattice and coupling parameter values. Two types of collective excitations that play a role in many dynamic magnetic processes are spin waves (magnons) and spinons. Our experiments enable us to study both types of excitations. First, we have been able to map the standing spin wave modes of a ferromagnetic bit of six atoms, and to determine their role in the collective reversal process of the bit (Spinelli et al., Nature Materials 2014). More recently, we have crafted antiferromagnetic spin 1/2 XXZ chains, which allow us to observe spinon excitations, as well as the stepwise transition to a fully aligned phase beyond the critical magnetic field (Toskovic et al., in preparation). These findings create a promising experimental environment for putting quantum magnetic models to the test. Research funded by NWO and FOM.

  4. Nonlocal electron transport in magnetized plasmas with arbitrary atomic number

    SciTech Connect

    Bennaceur-Doumaz, D.; Bendib, A.

    2006-09-15

    The numerical solution of the steady-state electron Fokker-Planck equation perturbed with respect to a global equilibrium is presented in magnetized plasmas with arbitrary atomic number Z. The magnetic field is assumed to be constant and the electron-electron collisions are described by the Landau collision operator. The solution is derived in the Fourier space and in the framework of the diffusive approximation which captures the spatial nonlocal effects. The transport coefficients are deduced and used to close a complete set of nonlocal electron fluid equations. This work improves the results of A. Bendib et al. [Phys. Plasmas 9, 1555 (2002)] and of A. V. Brantov et al. [Phys. Plasmas 10, 4633 (2003)] restricted to the local and nonlocal high-Z plasma approximations, respectively. The influence of the magnetic field on the nonlocal effects is discussed. We propose also accurate numerical fits of the relevant transport coefficients with respect to the collisionality parameter {lambda}{sub ei}/L and the atomic number Z, where L is the typical scale length and {lambda}{sub ei} is the electron-ion mean-free-path.

  5. Nanoscale magnetic resonance imaging and magnetic sensing using atomic defects in diamond

    NASA Astrophysics Data System (ADS)

    Grinolds, Michael

    Magnetic resonance imaging (MRI) has revolutionized modern medicine by providing non-invasive, chemically selective, three-dimensional imaging of living organisms. Industrial-scale MRI has the capability to image with millimeter-scale spatial resolution and has the sensitivity to detect as few as 1014 nuclear spins. Increasing spatial resolution to the atomic scale and sensitivity to the single-spin level would enable a wide array of applications most notably including imaging molecular structur. However, conventional MRI methods are already highly optimized, and further order-of-magnitude-scale improvements cannot be reasonably expected without employing fundamentally different technologies. This thesis presents an alternative approach to conventional MRI that pushes resolution and sensitivity to the individual atom and molecular level. The guiding principle for achieving multiple order-of-magnitude improvements is to miniaturize the key components of MRI: the detector and the source of magnetic-field gradients. By scaling down the physical size of these components to the nano- and atomic- scales, the signals from individual spins become measurable and resolvable. To miniature the detector, we employ an optically-active, paramagnetic atomic defect in diamond---a nitrogen-vacancy (NV) center---as our sensor. Owing to its optical readout, long coherence times, atomic-size, and room-temperature compatibility, NV centers in diamond have the capability to measure the magnetic fields from individual spins, provided the sensor can be placed sufficiently close to a target to be measured. This thesis describes the experimental realization of a microscope that can perform sensitive magnetometry experiments using a single NV center that magnetically images by spatially scanning the NV center within a few nanometers of magnetic targets. With this technique we are able to demonstrate the first room-temperature magnetic imaging of individual electron spins. For miniaturizing

  6. Spin-polarized currents generated by magnetic Fe atomic chains.

    PubMed

    Lin, Zheng-Zhe; Chen, Xi

    2014-06-13

    Fe-based devices are widely used in spintronics because of high spin-polarization and magnetism. In this work, freestanding Fe atomic chains, the thinnest wires, were used to generate spin-polarized currents due to the spin-polarized energy bands. By ab initio calculations, the zigzag structure was found to be more stable than the wide-angle zigzag structure and had a higher ratio of spin-up and spin-down currents. By our theoretical prediction, Fe atomic chains have a sufficiently long thermal lifetime only at T ≦̸ 150 K, while C atomic chains are very stable even at T = 1000 K. This means that the spintronic devices based on Fe chains could work only at low temperatures. A system constructed by a short Fe chain sandwiched between two graphene electrodes could be used as a spin-polarized current generator, while a C chain could not be used in this way. The present work may be instructive and meaningful to further practical applications based on recent technical developments on the preparation of metal atomic chains (Proc. Natl. Acad. Sci. USA 107 9055 (2010)). PMID:24849670

  7. First principles calculation of the structural, electronic, and magnetic properties of Au-Pd atomic chains

    SciTech Connect

    Dave, Mudra R.; Sharma, A. C.

    2015-06-24

    The structural, electronic and magnetic properties of free standing Au-Pd bimetallic atomic chain is studied using ab-initio method. It is found that electronic and magnetic properties of chains depend on position of atoms and number of atoms. Spin polarization factor for different atomic configuration of atomic chain is calculated predicting a half metallic behavior. It suggests a total spin polarised transport in these chains.

  8. Extended Bose-Hubbard models with ultracold magnetic atoms

    NASA Astrophysics Data System (ADS)

    Baier, S.; Mark, M. J.; Petter, D.; Aikawa, K.; Chomaz, L.; Cai, Z.; Baranov, M.; Zoller, P.; Ferlaino, F.

    2016-04-01

    The Hubbard model underlies our understanding of strongly correlated materials. Whereas its standard form only comprises interactions between particles at the same lattice site, extending it to encompass long-range interactions is predicted to profoundly alter the quantum behavior of the system. We realize the extended Bose-Hubbard model for an ultracold gas of strongly magnetic erbium atoms in a three-dimensional optical lattice. Controlling the orientation of the atomic dipoles, we reveal the anisotropic character of the onsite interaction and hopping dynamics and their influence on the superfluid-to-Mott insulator quantum phase transition. Moreover, we observe nearest-neighbor interactions, a genuine consequence of the long-range nature of dipolar interactions. Our results lay the groundwork for future studies of exotic many-body quantum phases.

  9. Extended Bose-Hubbard models with ultracold magnetic atoms.

    PubMed

    Baier, S; Mark, M J; Petter, D; Aikawa, K; Chomaz, L; Cai, Z; Baranov, M; Zoller, P; Ferlaino, F

    2016-04-01

    The Hubbard model underlies our understanding of strongly correlated materials. Whereas its standard form only comprises interactions between particles at the same lattice site, extending it to encompass long-range interactions is predicted to profoundly alter the quantum behavior of the system. We realize the extended Bose-Hubbard model for an ultracold gas of strongly magnetic erbium atoms in a three-dimensional optical lattice. Controlling the orientation of the atomic dipoles, we reveal the anisotropic character of the onsite interaction and hopping dynamics and their influence on the superfluid-to-Mott insulator quantum phase transition. Moreover, we observe nearest-neighbor interactions, a genuine consequence of the long-range nature of dipolar interactions. Our results lay the groundwork for future studies of exotic many-body quantum phases. PMID:27124454

  10. Magnetic blackbody shift of hyperfine transitions for atomic clocks

    SciTech Connect

    Berengut, J. C.; Flambaum, V. V.; King-Lacroix, J.

    2009-12-15

    We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T{sup 2} dependence only in the high-temperature limit. We also calculate the shift of ground-state p{sub 1/2} hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p{sub 3/2} fine-structure multiplet may be the dominant effect.

  11. Microfabricated atomic vapor cell arrays for magnetic field measurements

    SciTech Connect

    Woetzel, S.; Schultze, V.; IJsselsteijn, R.; Schulz, T.; Anders, S.; Stolz, R.; Meyer, H.-G.

    2011-03-15

    We describe a method for charging atomic vapor cells with cesium and buffer gas. By this, it is possible to adjust the buffer gas pressure in the cells with good accuracy. Furthermore, we present a new design of microfabricated vapor cell arrays, which combine silicon wafer based microfabrication and ultrasonic machining to achieve the arrays of thermally separated cells with 50 mm{sup 3} volume. With cells fabricated in the outlined way, intrinsic magnetic field sensitivities down to 300 fT/Hz{sup 1/2} are reached.

  12. Resonant interaction of trapped cold atoms with a magnetic cantilever tip

    NASA Astrophysics Data System (ADS)

    Montoya, Cris; Valencia, Jose; Geraci, Andrew A.; Eardley, Matthew; Moreland, John; Hollberg, Leo; Kitching, John

    2015-06-01

    Magnetic resonance in an ensemble of laser-cooled trapped Rb atoms is excited using a microcantilever with a magnetic tip. The cantilever is mounted on a multilayer chip designed to capture, cool, and magnetically transport cold atoms. The coupling is observed by measuring the loss from a magnetic trap as the oscillating cantilever induces Zeeman-state transitions in the atoms. Interfacing cold atoms with mechanical devices could enable probing and manipulating atomic spins with nanometer spatial resolution and single-spin sensitivity, leading to new capabilities in quantum computation, quantum simulation, and precision sensing.

  13. Magnetic induction measurements using an all-optical {sup 87}Rb atomic magnetometer

    SciTech Connect

    Wickenbrock, Arne; Tricot, François; Renzoni, Ferruccio

    2013-12-09

    In this work we propose, and experimentally demonstrate, the use of a self-oscillating all-optical atomic magnetometer for magnetic induction measurements. Given the potential for miniaturization of atomic magnetometers, and their extreme sensitivity, the present work shows that atomic magnetometers may play a key role in the development of instrumentation for magnetic induction tomography.

  14. Precession Control on Precipitation in the Western Pacific Warm Pool Inferred from Environmental Magnetism

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.

    2014-12-01

    The Western Pacific Warm Pool (WPWP) has highest water temperature in the global ocean, and its spatiotemporal variations have significant impacts on large-scale atmospheric circulation and global hydrology. An environmental magnetic study was conducted on sediment cores of late Pleistocene age taken from the West Caroline Basin (WCB) offshore northern New Guinea in order to constrain hydrological variability over the WPWP on orbital timescales. Magnetite dominates magnetic mineral assemblages of the sediments. This is evidenced by that IRM acquisition curves are mostly explained by a low-coercivity component, and that the Verwey transition was obvious in low-temperature measurements. Existence of the sharp central ridges on FORC diagrams and TEM images indicate the occurrence of biogenic magnetite. Compared with pelagic sediments from other regions, however, FORC diagrams show a larger contribution of an interacting PSD and MD component, and the ratios of ARM susceptibility to SIRM (kARM/SIRM) are lower, which suggests a larger proportion of the terrigenous component. This is probably due to a large terrigenous sediment input from nearby land, New Guinea, induced by high precipitation in the intertropical convergence zone. Magnetic susceptibility (k) and kARM/SIRM well correlate with northern-hemisphere summer insolation. Maxima in k and minima in kARM/SIRM correspond to insolation minima, which suggests a larger terrigenous input caused by higher precipitation at these times. Interestingly, in the western part of WCB, k variations are dominated by the eccentricity periodicity and mimic δ18O curves, but the precession periodicity prevails in kARM/SIRM. These cores were taken at depths close to the CCD, and thus the k variations cannot be explained by dilution with carbonates. Sedimentation influenced by global sea-level changes may control the k variations; this part of the basin is adjacent to a wider continental shelf compared with the eastern part of WCB.

  15. A Strongly-Coupled Average Atom Model for Warm Dense Mixtures

    NASA Astrophysics Data System (ADS)

    Stanton, Liam; Murillo, Michael; Cimarron Project Collaboration

    2013-10-01

    We present a new average atom model to determine the properties of dense, multi-component plasmas. Strong ion correlations are taken into account through the quantum Ornstein-Zernike relations and hypernetted-chain closures, while an orbital-free density functional theory is employed to calculate electronic structure. The formalism is derived without reference to a mean ionization state of the system which allows for a more consistent generalization to mixtures. Applications to EOS and XRTS are discussed, and numerical simulations are compared with other methods and experimental data. Prepared by LLNL under Contract DE-AC52-07NA27344.

  16. Artificial Staggered Magnetic Field for Ultracold Atoms in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Morais Smith, Cristiane

    2011-03-01

    Uniform magnetic fields are ubiquitous in nature, but this is not the case for staggered magnetic fields. In this talk, I will discuss an experimental set-up for cold atoms recently proposed by us, which allows for the realization of a ``staggered gauge field'' in a 2D square optical lattice. If the lattice is loaded with bosons, it may be described by an effective Bose-Hubbard Hamiltonian, with complex and anisotropic hopping coefficients. A very rich phase diagram emerges: besides the usual Mott-insulator and zero-momentum condensate, a new phase with a finite momentum condensate becomes the ground-state at strong gauge fields. By using the technique of Feshbach resonance, the dynamics of a coherent superposition of a vortex-carrying atomic condensate and a conventional zero-momentum molecular condensate can also be studied within the same scheme. On the other hand, if the lattice is loaded with fermions, a highly tunable, graphene-like band structure can be realized, without requiring the honeycomb lattice symmetry. When the system is loaded with a mixture of bosons and two-species fermions, several features of the high-Tc phase diagram can be reproduced. A dome-shaped unconventional superconducting region arises, surrounded by a non-Fermi liquid and a Fermi liquid at low and high doping, respectively. We acknowledge financial support from the Netherlands Organization for Scientific Research (NWO).

  17. Magnetic nanodots from atomic Fe: can it be done?

    PubMed

    te Sligte, E; Bosch, R C M; Smeets, B; van der Straten, P; Beijerinck, H C W; van Leeuwen, K A H

    2002-04-30

    Laser focusing of Fe atoms offers the possibility of creating separate magnetic structures on a scale of 10 nm with exact periodicity. This can be done by using the parabolic minima of the potential generated by a standing light wave as focusing lenses. To achieve the desired 10-nm resolution, we need to suppress chromatic and spherical aberrations, as well as prevent structure broadening caused by the divergence of the incoming beam. Chromatic aberrations are suppressed by the development of a supersonic Fe beam source with speed ratio S = 11 +/- 1. This beam has an intensity of 3 x 10(15) atoms sr(-1) s(-1). The spherical aberrations of the standing light wave will be suppressed by aperturing with beam masks containing 100-nm slits at 744-nm intervals. The beam divergence can be reduced by application of laser cooling to reduce the transverse velocity. We have constructed a laser system capable of delivering over 500 mW of laser light at 372 nm, the wavelength of the (5)D(4) --> (5)F(5) atomic transition of (56)Fe we intend to use for laser cooling. Application of polarization spectroscopy to a hollow cathode discharge results in a locking system holding the laser continuously within 2 MHz of the desired frequency. PMID:11917133

  18. Magnetic nanodots from atomic Fe: Can it be done?

    PubMed Central

    te Sligte, E.; Bosch, R. C. M.; Smeets, B.; van der Straten, P.; Beijerinck, H. C. W.; van Leeuwen, K. A. H.

    2002-01-01

    Laser focusing of Fe atoms offers the possibility of creating separate magnetic structures on a scale of 10 nm with exact periodicity. This can be done by using the parabolic minima of the potential generated by a standing light wave as focusing lenses. To achieve the desired 10-nm resolution, we need to suppress chromatic and spherical aberrations, as well as prevent structure broadening caused by the divergence of the incoming beam. Chromatic aberrations are suppressed by the development of a supersonic Fe beam source with speed ratio S = 11 ± 1. This beam has an intensity of 3 × 1015 atoms sr−1 s−1. The spherical aberrations of the standing light wave will be suppressed by aperturing with beam masks containing 100-nm slits at 744-nm intervals. The beam divergence can be reduced by application of laser cooling to reduce the transverse velocity. We have constructed a laser system capable of delivering over 500 mW of laser light at 372 nm, the wavelength of the 5D4 → 5F5 atomic transition of 56Fe we intend to use for laser cooling. Application of polarization spectroscopy to a hollow cathode discharge results in a locking system holding the laser continuously within 2 MHz of the desired frequency. PMID:11917133

  19. Cold and Warm Atomic Gas around the Perseus Molecular Cloud. I. Basic Properties

    NASA Astrophysics Data System (ADS)

    Stanimirović, Snežana; Murray, Claire E.; Lee, Min-Young; Heiles, Carl; Miller, Jesse

    2014-10-01

    Using the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (Ts ) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ~15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with >~ 85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear candidates for

  20. Cold and warm atomic gas around the Perseus molecular cloud. I. Basic properties

    SciTech Connect

    Stanimirović, Snežana; Murray, Claire E.; Miller, Jesse; Lee, Min-Young

    2014-10-01

    Using the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (T{sub s} ) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ∼15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with ≳ 85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear

  1. Reaching the magnetic anisotropy limit of a 3d metal atom.

    PubMed

    Rau, Ileana G; Baumann, Susanne; Rusponi, Stefano; Donati, Fabio; Stepanow, Sebastian; Gragnaniello, Luca; Dreiser, Jan; Piamonteze, Cinthia; Nolting, Frithjof; Gangopadhyay, Shruba; Albertini, Oliver R; Macfarlane, Roger M; Lutz, Christopher P; Jones, Barbara A; Gambardella, Pietro; Heinrich, Andreas J; Brune, Harald

    2014-05-30

    Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism. PMID:24812206

  2. Magnetic conveyor belt transport of ultracold atoms to a superconducting atomchip

    NASA Astrophysics Data System (ADS)

    Minniberger, Stefan; Diorico, Fritz; Haslinger, Stefan; Hufnagel, Christoph; Novotny, Christian; Lippok, Nils; Majer, Johannes; Koller, Christian; Schneider, Stephan; Schmiedmayer, Jörg

    2014-09-01

    We report the realization of a robust magnetic transport scheme to bring >3 × 108 ultracold 87Rb atoms into a cryostat. The sequence starts with standard laser cooling and trapping of 87Rb atoms, transporting first horizontally and then vertically through the radiation shields into a cryostat by a series of normal- and superconducting magnetic coils. Loading the atoms in a superconducting microtrap paves the way for studying the interaction of ultracold atoms with superconducting surfaces and quantum devices requiring cryogenic temperatures.

  3. Determination of the line shapes of atomic nitrogen resonance lines by magnetic scans

    NASA Technical Reports Server (NTRS)

    Lawrence, G. M.; Stone, E. J.; Kley, D.

    1976-01-01

    A technique is given for calibrating an atomic nitrogen resonance lamp for use in determining column densities of atoms in specific states. A discharge lamp emitting the NI multiplets at 1200 A and 1493 A is studied by obtaining absorption by atoms in a magnetic field (0-2.5 T). This magnetic scanning technique enables the determination of the absorbing atom column density, and an empirical curve of growth is obtained because the atomic f-value is known. Thus, the calibrated lamp can be used in the determination of atomic column densities.

  4. Chern Insulators from Heavy Atoms on Magnetic Substrates

    NASA Astrophysics Data System (ADS)

    Garrity, Kevin

    2014-03-01

    Chern insulators, or quantum anomalous Hall insulators, would display a variety interesting and potentially useful properties; however, existing methods for constructing Chern insulators have proven challenging, and have thus far been limited to low temperatures. We propose a new method for searching for Chern insulators by depositing atomic layers of elements with large spin-orbit coupling (e.g., Bi) on the surface of a magnetic insulator. We argue that such systems will typically have isolated surface bands with nonzero Chern numbers. If these bands overlap in energy, a metallic surface with large anomalous Hall conductivity will result; if not, a Chern-insulator state will typically occur. We use first principles calculations to verify this search strategy by considering heavy atoms on the surfaces of MnTe, MnSe, and EuS, as well as more recent results on several promising oxide and nitride surfaces. We find many Chern insulators in both cases, including examples with large band gaps.

  5. Magnetic Slowing Down of Spin Relaxation due to Binary Collisions of Alkali-Metal Atoms with Buffer-Gas Atoms

    NASA Astrophysics Data System (ADS)

    Walter, D. K.; Griffith, W. M.; Happer, W.

    2002-03-01

    We report the first studies of magnetic decoupling of the spin relaxation of alkali-metal atoms due to binary collisions with buffer gases. When binary collisions are the dominant relaxation mechanism, the relaxation and its magnetic decoupling are well described by the S-damping rate ΓSD due to the spin-rotation interaction γN˙S, the spin exchange rate ΓEX for collisions between alkali atoms, and a new ``Carver rate'' ΓC, due to the pressure-shift interaction δAİS, which can substantially broaden the magnetic decoupling curve while having no influence on the zero-field rates.

  6. Mapping magnetism with atomic resolution using aberrated electron probes

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan; Rusz, Ján; McGuire, Michael A.; Symons, Christopher T.; Vatsavai, Ranga Raju; Lupini, Andrew R.

    2015-03-01

    In this talk, we report a direct experimental real-space mapping of magnetic circular dichroism with atomic resolution in aberration-corrected scanning transmission electron microscopy (STEM). Using an aberrated electron probe with customized phase distribution, we reveal with electron energy-loss (EEL) spectroscopy the checkerboard antiferromagnetic ordering of Mn moments in LaMnAsO by observing a dichroic signal in the Mn L-edge. The aberrated probes allow the collection of EEL spectra using the transmitted beam, which results in a magnetic circular dichroic signal with intrinsically larger signal-to-noise ratios than those obtained via nanodiffraction techniques (where most of the transmitted electrons are discarded). The novel experimental setup presented here, which can easily be implemented in aberration-corrected STEM, opens new paths for probing dichroic signals in materials with unprecedented spatial resolution. This research was supported by DOE SUFD MSED, by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the US DOE, and by the Swedish Research Council and Swedish National Infrastructure for Computing (NSC center)

  7. Three-dimensional magnetic trap lattice on an atom chip with an optically induced fictitious magnetic field

    SciTech Connect

    Yan Hui

    2010-05-15

    A robust type of three-dimensional magnetic trap lattice on an atom chip combining optically induced fictitious magnetic field with microcurrent-carrying wires is proposed. Compared to the regular optical lattice, the individual trap in this three-dimensional magnetic trap lattice can be easily addressed and manipulated.

  8. Magnetic levitation for effective loading of cold cesium atoms in a crossed dipole trap

    NASA Astrophysics Data System (ADS)

    Li, Yuqing; Feng, Guosheng; Xu, Rundong; Wang, Xiaofeng; Wu, Jizhou; Chen, Gang; Dai, Xingcan; Ma, Jie; Xiao, Liantuan; Jia, Suotang

    2015-05-01

    We report a detailed study of effective magnetically levitated loading of cold atoms in a crossed dipole trap: an appropriate magnetic field gradient precisely compensates for the destructive gravitational force of the atoms and an additional bias field simultaneously eliminates the antitrapping potential induced by the magnetic field gradient. The magnetic levitation is required for a large-volume crossed dipole trap to form a shallow but very effective loading potential, making it a promising method for loading and trapping more cold atoms. For cold cesium atoms in the F =3 , m F =3 state prepared by three-dimensional degenerated Raman sideband cooling, a large number of atoms ˜3.2 ×106 have been loaded into a large-volume crossed dipole trap with the help of the magnetic levitation technique. The dependence of the number of atoms loaded and trapped in the dipole trap on the magnetic field gradient and bias field, respectively, is in good agreement with the theoretical analysis. The optimum magnetic field gradient of 31.13 G/cm matches the theoretical value of 31.3 G/cm well. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for many atomic species in high-field seeking states.

  9. Atomic site sensitivity of the energy loss magnetic chiral dichroic spectra of complex oxides

    SciTech Connect

    Calmels, L.; Rusz, J.

    2011-04-01

    The quantitative analysis of magnetic oxide core level spectra can become complicated when the magnetic atoms are located at several nonequivalent atomic sites in the crystal. This is, for instance, the case for Fe atoms in magnetite, which are located in tetrahedral and octahedral atomic sites; in this case, the x-ray magnetic circular dichroic (XMCD) spectra recorded at the L{sub 2,3} edge of Fe contain contributions from the different nonequivalent atomic sites, which unfortunately cannot be separated. Energy loss magnetic chiral dichroic (EMCD) spectra are the transmission electron microscope analogies of the XMCD spectra. One of the important differences between these two techniques of magnetic analysis is that EMCD uses a fast electron beam instead of polarized light. The fast electrons behave like Bloch states in the sample, and the fine structure of the EMCD spectra is strongly influenced by channeling and dynamical diffraction effects. These effects can be adjusted by changing the experimental configuration. We use theoretical calculations, which include dynamical diffraction effects and in which electronic transitions are treated in the atomic multiplet formalism, to show that the relative weight of the Fe atoms in different nonequivalent atomic sites can be changed by a proper choice of the position of the detector and of the magnetite sample orientation and thickness. We conclude that EMCD spectra could be used to isolate the magnetic contribution of atoms in each of the nonequivalent atomic sites, which would not be possible with XMCD techniques.

  10. Effect of magnetism and atomic order on static atomic displacements in the Invar alloy Fe-27 at.% Pt

    NASA Astrophysics Data System (ADS)

    Sax, C. R.; Schönfeld, B.; Ruban, A. V.

    2015-08-01

    Fe-27 at.% Pt was aged at 1123 K and quenched to room temperature (RT) to set up a state of thermal equilibrium. The local atomic arrangement was studied by diffuse x-ray scattering above (at 427 K) and below (at RT) the Curie temperature as well as at RT under a saturating magnetic field. The separated short-range order scattering remained unchanged for all three states, with maxima at 100 positions. Effective pair interaction parameters determined by the inverse Monte Carlo method gave an order-disorder transition temperature of about 1088 K, close to direct experimental findings. The species-dependent static atomic displacements for the first two shells show large differences, with a strong increase in magnitude from the state at 427 K over RT to the state under saturating magnetic field. This outcome is in agreement with an increase in atomic volume of Fe with increasing local magnetic moment. Electronic-structure calculations closely reproduce the values for the static atomic displacements in the ferromagnetic state, and predict their dependence on the atomic configuration. They also reveal a strong dependence of the magnetic exchange interactions in Fe-Pt on the atomic configuration state and lattice parameter. In particular, the increase of the Curie temperature in a random state relative to that in the ordered one is demonstrated to be related to the corresponding change of the magnetic exchange interactions due to the different local atomic chemical environment. There exists a similar strong concentration dependence of the chemical interactions as in the case of magnetic exchange interactions. Theoretical effective interactions for Fe-27 at.% Pt alloy are in good agreement with experimental results, and they also reproduce well the L1 2-A1 transition temperature.

  11. Manipulation of magnetic anisotropy in Irn+1 clusters by Co atom

    NASA Astrophysics Data System (ADS)

    Ge, Gui-Xian; Yan, Hong-Xia; Yang, Jue-Ming; Zhou, Long; Wan, Jian-Guo; Zhao, Ji-Jun; Wang, Guang-Hou

    2016-07-01

    Based on the first principles calculations, we have investigated the magnetic properties of Irn+1 clusters modulated by Co atoms. The research conclusions show that the amplitude of magnetic anisotropy energy (MAE) and magnetization direction of the small Irn+1 can be manipulated by Co atom if we can control the size very precisely. Such regulatory mechanism of MAE is ascribed to the distributing variation of Ir-5d orbits around the Fermi level induced by Co atom. More importantly, the colossal MAE values, 67.4 meV/atom, 40.26 meV/atom and 91.37 meV/atom, can be obtained for Ir2, Ir4, and CoIr clusters, respectively. Such high values provide a promising avenue for developing high-density magnetic storage units at sub-nanometer size.

  12. Observation of individual neutral atoms in magnetic and magneto-optical traps

    NASA Astrophysics Data System (ADS)

    Haubrich, D.; Schadwinkel, H.; Strauch, F.; Ueberholz, B.; Wynands, R.; Meschede, D.

    1996-06-01

    We have identified and photographed individual cesium atoms in a magneto-optical trap with steep magnetic gradients. By switching off the trapping light fields, single atoms were released to a bound state of the magnetic potential. A storage time of 38 s was measured for purely magnetic trapping, whereas a storage time of 147 s was observed in the corresponding magneto-optical trap.

  13. Magnetic-sublevel atomic kinetics modeling for line polarization spectroscopy

    SciTech Connect

    Hakel, P.; Mancini, R. C.

    2004-01-01

    We discuss the mechanism of polarized X-ray line emission in plasmas, its connection to plasma anisotropy, and introduce an atomic kinetics model and code (POLAR) based on the population kinetics of magnetic sublevels. POLAR represents a multi-level, multi-process approach to the problem of polarized spectra in plasmas, and hence it is well suited for plasma applications where cascade effects and alignment transfer can become important. Polarization degrees of X-ray spectral lines computed with POLAR were successfully benchmarked against calculations done with other formalisms, and experimental results obtained at the EBIT facility of Lawrence Livermore National Laboratory. We also investigated the polarization of He-like Si X-ray satellite lines as spectral signatures of anisotropy in the electron distribution function. A comprehensive modeling study was performed taking into account hydrodynamics and electron kinetics. We find that two satellite lines connecting singlet states develop a noticeable polarization while the triplet lines remain unpolarized. These results suggest a scenario where triplet lines could be used as a reference while the singlets could be used as polarized markers of plasma anisotropy.

  14. Trapping cold molecules and atoms: Simultaneous magnetic deceleration and trapping of cold molecular Oxygen with Lithium atoms

    NASA Astrophysics Data System (ADS)

    Akerman, Nitzan; Karpov, Michael; Segev, Yair; Bibelink, Natan; Narevicius, Julia; Narevicius, Edvardas

    2016-05-01

    Cooling molecules to the ultra-cold regime remains a major challenge in the growing field of cold molecules. The molecular internal degrees of freedom complicate the effort of direct application of laser cooling. An alternative and general path towards ultra-cold molecules relies on sympathetic cooling via collisions with laser-cooled atoms. Here, we demonstrate the first step towards application of sympathetic cooling by co-trapping of molecular Oxygen with Lithium atoms in a magnetic trap at a temperature of 300 mK. Our experiment begins with a pulsed supersonic beam which is a general source for cold high-flux atomic and molecular beams. Although the supersonic expansion efficiently cools the beam to temperatures below 1K, it also accelerates the beam to high mean velocities. We decelerate a beam of O2 in a moving magnetic trap decelerator from 375 m/s to a stop. We entrained the molecular beam with Li atoms by laser ablation prior to deceleration. The deceleration ends with loading the molecules and atoms into a static quadrupole trap, which is generated by two permanent magnets. We estimate 109 trapped molecules with background limited lifetime of 0.6 Sec. Our achievement enables application of laser cooling on the Li atoms in order to sympathetically cool the O2.

  15. Effects of warm temper rolling on microstructure, texture and magnetic properties of strip-casting 6.5 wt% Si electrical steel

    NASA Astrophysics Data System (ADS)

    Li, Hao-Ze; Liu, Hai-Tao; Liu, Yi; Liu, Zhen-Yu; Cao, Guang-Ming; Luo, Zhong-Han; Zhang, Feng-Quan; Chen, Sheng-Lin; Lyu, Li; Wang, Guo-Dong

    2014-12-01

    6.5 wt% Si electrical steel thin sheets were produced by a processing route including strip casting, hot rolling, warm rolling, intermediate annealing, warm temper rolling and final annealing, in which the warm temper rolling reduction varied from 2.7% to 14.4%. A detailed study of the microstructural and textural evolutions through the whole processing route was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The findings revealed that the final recrystallization microstructure, texture and magnetic properties relied heavily on the warm temper rolling reduction. As the warm temper rolling reduction increased from 2.7% to 14.4%, the finally recrystallized microstructures were more homogeneous and the average grain size was decreased. At the warm temper rolling reduction lower than 7.0%, the occurrence of the exaggeratedly large annealing grains which dominated the whole sheet thickness resulted in strong <001>//ND fiber, parallel α-fiber, <111>//ND fiber and many other strong hard-magnetization texture components. By contrast, at the warm temper rolling reduction higher than 7.0%, the recrystallization textures were characterized by weak <001>//ND fiber, parallel α-fiber, <111>//ND texture, together with fewer and weak hard-magnetization texture components. The mechanism responsible for the finally microstructural and textural changes was explained by strain induced boundary migration. As warm temper rolling reduction increased, the magnetic properties at high frequency were gradually improved due to smaller grain sizes and more desirable textures. The highest magnetic inductions of 1.383 T (B8), 1.484 T (B25) and 1.571 T (B50) in combination with the lowest iron losses at high frequencies of 19.11 W/Kg (W10/400) and 3.824 W/Kg (W2/1000) were obtained at 14.4% warm temper rolling reduction under the applied condition.

  16. Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.

    PubMed

    Baumann, S; Donati, F; Stepanow, S; Rusponi, S; Paul, W; Gangopadhyay, S; Rau, I G; Pacchioni, G E; Gragnaniello, L; Pivetta, M; Dreiser, J; Piamonteze, C; Lutz, C P; Macfarlane, R M; Jones, B A; Gambardella, P; Heinrich, A J; Brune, H

    2015-12-01

    We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0±0.3  meV/atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment. PMID:26684139

  17. Magnetic coupling of laser-cooled atoms to a micro-resonator

    NASA Astrophysics Data System (ADS)

    Geraci, Andrew; Wang, Ying-Ju; Eardley, Matthew; Moreland, John; Kitching, John

    2009-05-01

    The direct coupling of the spin-degrees of freedom of an atomic vapor to the vibrational motion of a magnetic cantilever tip has recently been demonstrated [1], and prospects for coupling a BEC on an atom-chip to a nano- mechanical resonator have been recently discussed [2]. Possible applications include chip-scale atomic devices, in which localized interactions with magnetic cantilever tips selectively influence or probe atomic spins. As a next step towards the realization of a strongly coupled ultra-cold atom- resonator system, we have constructed an apparatus to study the direct coupling between the spins of trapped laser-cooled Rb atoms and a magnetic tip on a micro-cantilever. The atoms will be loaded into a magnetic trap formed by the cantilever tip and external magnetic fields. The cantilever will be driven capacitively at its resonance frequency, resulting in a coherent precession of the trapped atomic spins with a matching Larmor frequency. Prospects for measuring the back-action of the ensemble of atomic spins on a cantilever beam will also be discussed. [1] Y.-J. Wang,M. Eardley, S. Knappe, J. Moreland, L. Hollberg, and J. Kitching, PRL 97, 227602 (2006). [2] P. Treutlein,D. Hunger, S. Camerer, T. W. Hansch, and J. Reichel, PRL 99, 140403 (2007).

  18. Magnetic dipole-dipole sensing at atomic scale using electron spin resonance STM

    NASA Astrophysics Data System (ADS)

    Choi, T.; Paul, W.; Rolf-Pissarczyk, S.; MacDonald, A.; Yang, K.; Natterer, F. D.; Lutz, C. P.; Heinrich, A. J.

    Magnetometry having both high magnetic field sensitivity and atomic resolution has been an important goal for applications in diverse fields covering physics, material science, and biomedical science. Recent development of electron spin resonance STM (ESR-STM) promises coherent manipulation of spins and studies on magnetic interaction of artificially built nanostructures, leading toward quantum computation, simulation, and sensors In ESR-STM experiments, we find that the ESR signal from an Fe atom underneath a STM tip splits into two different frequencies when we position an additional Fe atom nearby. We measure an ESR energy splitting that decays as 1/r3 (r is the separation of the two Fe atoms), indicating that the atoms are coupled through magnetic dipole-dipole interaction. This energy and distance relation enables us to determine magnetic moments of atoms and molecules on a surface with high precision in energy. Unique and advantageous aspects of ESR-STM are the atom manipulation capabilities, which allow us to build atomically precise nanostructures and examine their interactions. For instance, we construct a dice cinque arrangement of five Fe atoms, and probe their interaction and energy degeneracy. We demonstrate the ESR-STM technique can be utilized for quantum magnetic sensors.

  19. Planar hydrogen-like atom in inhomogeneous magnetic fields: Exactly or quasi-exactly solvable models

    NASA Astrophysics Data System (ADS)

    Liu, Liyan; Hao, Qinghai

    2015-05-01

    We use a simple mathematical method to solve the problem of a two-dimensional hydrogen-like atom in the inhomogeneous magnetic fields B = ( k/ r)z and B = ( k/ r 3)z. We construct a Hamiltonian that takes the same form as the Hamiltonian of a hydrogen-like atom in the homogeneous magnetic fields and obtain the energy spectrum by comparing the Hamiltonians. The results show that the whole spectrum of the atom in the magnetic field B = ( k/ r)z can be obtained, and the problem is exactly solvable in this case. We find analytic solutions of the Schrödinger equation for the atom in the magnetic field B = ( k/ r 3)z for particular values of the magnetic strength k and thus present a quasi-exactly solvable model.

  20. Simultaneous differential measurement of a magnetic-field gradient by atom interferometry using double fountains

    SciTech Connect

    Hu Zhongkun; Duan Xiaochun; Zhou Minkang; Sun Buliang; Zhao Jinbo; Huang Maomao; Luo Jun

    2011-07-15

    Precisely measuring the magnetic-field gradient within a vacuum chamber is important for many precision experiments and can be realized by atom interferometry using magnetically sensitive sublevels at different times to make a differential measurement, which had been demonstrated in our previous work. In this paper, we demonstrate a differential method to measure the magnetic-field gradient by means of two simultaneously operated atom interferometers using double atomic fountains. By virtue of this simultaneous differential measurement to reject common-mode noise, the resolution can be improved by one order of magnitude for about a 1000-s integration time.

  1. The effect of grading the atomic number at resistive guide element interface on magnetic collimation

    NASA Astrophysics Data System (ADS)

    Alraddadi, R. A. B.; Robinson, A. P. L.; Woolsey, N. C.; Pasley, J.

    2016-07-01

    Using 3 dimensional numerical simulations, this paper shows that grading the atomic number and thus the resistivity at the interface between an embedded high atomic number guide element and a lower atomic number substrate enhances the growth of a resistive magnetic field. This can lead to a large integrated magnetic flux density, which is fundamental to confining higher energy fast electrons. This results in significant improvements in both magnetic collimation and fast-electron-temperature uniformity across the guiding. The graded interface target provides a method for resistive guiding that is tolerant to laser pointing.

  2. Efficient magnetic guiding and deflection of atomic beams with moderate velocities

    NASA Astrophysics Data System (ADS)

    Goepfert, A.; Lison, F.; Schütze, R.; Wynands, R.; Haubrich, D.; Meschede, D.

    We have studied guidance and deflection of a beam of cesium atoms by a strong toroidal magnetic quadrupole field. The beam guide is made from permanent magnets sustaining a radial field gradient of 2.8 T/cm. Atoms with moderate longitudinal velocities ranging from 30 m/s to 70 m/s were inserted across the 10-mm-diameter aperture of a 24.5° arc with radius 300 mm. We have measured transmission and beam divergence and find good agreement with ray-tracing calculations and analytical estimates. The magnetic beam guide allows for 100% transmission of heavy atoms over large angles.

  3. Extracting the differential phase in dual atom interferometers by modulating magnetic fields

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Ping; Zhong, Jia-Qi; Chen, Xi; Li, Run-Bing; Li, Da-Wei; Zhu, Lei; Song, Hong-Wei; Wang, Jin; Zhan, Ming-Sheng

    2016-09-01

    We present a new scheme for measuring the differential phase in dual atom interferometers. The magnetic field is modulated in one interferometer, and the differential phase can be extracted without measuring the amplitude of the magnetic field by combining the ellipse and linear fitting methods. The gravity gradient measurements are discussed based on dual atom interferometers. Numerical simulation shows that the systematic error of the differential phase measurement is largely decreased when the duration of the magnetic field is symmetrically modulated. This combined fitting scheme has a high accuracy for measuring an arbitrary differential phase in dual atom interferometers.

  4. Magnetic Resonance in an Atomic Vapor Excited by a Mechanical Resonator

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Ju; Eardley, Matthew; Knappe, Svenja; Moreland, John; Hollberg, Leo; Kitching, John

    2006-12-01

    We demonstrate a direct resonant interaction between the mechanical motion of a mesoscopic resonator and the spin degrees of freedom of a sample of neutral atoms in the gas phase. This coupling, mediated by a magnetic particle attached to the tip of the miniature mechanical resonator, excites a coherent precession of the atomic spins about a static magnetic field. The novel coupled atom-resonator system may enable development of low-power, high-performance sensors, and enhance research efforts connected with the manipulation of cold atoms, quantum control, and high-resolution microscopy.

  5. Laser cooling of an indium atomic beam enabled by magnetic fields

    NASA Astrophysics Data System (ADS)

    Klöter, B.; Weber, C.; Haubrich, D.; Meschede, D.; Metcalf, H.

    2008-03-01

    We demonstrate magnetic field enabled optical forces on a neutral indium atomic beam in a light field consisting of five frequencies. The role of dark magnetic ground state sublevels is studied and enables us to cool the atomic beam transversely to near the Doppler limit with laser frequencies tuned above the atomic resonance. The effect of laser cooling can be explained with transient effects in the light potential created by the standing wave light field where the atoms are optically pumped into the dark states and recycled by Larmor precession.

  6. Association of atoms into universal dimers using an oscillating magnetic field.

    PubMed

    Langmack, Christian; Smith, D Hudson; Braaten, Eric

    2015-03-13

    In a system of ultracold atoms near a Feshbach resonance, pairs of atoms can be associated into universal dimers by an oscillating magnetic field with a frequency near that determined by the dimer binding energy. We present a simple expression for the transition rate that takes into account many-body effects through a transition matrix element of the contact. In a thermal gas, the width of the peak in the transition rate as a function of the frequency is determined by the temperature. In a dilute Bose-Einstein condensate of atoms, the width is determined by the inelastic scattering rates of a dimer with zero-energy atoms. Near an atom-dimer resonance, there is a dramatic increase in the width from inelastic atom-dimer scattering and from atom-atom-dimer recombination. The recombination contribution provides a signature for universal tetramers that are Efimov states consisting of two atoms and a dimer. PMID:25815927

  7. EBIT in the Magnetic Trapping Mode: Mass Spectrometry, Atomic Lifetime Measurements, and Charge Transfer Reactions of Highly Charged Atomic Ions

    SciTech Connect

    Schweikhard, L; Beiersdorfer, P; Trabert, E

    2001-07-10

    Although it may sound like a contradiction in terms, the electron beam ion trap (EBIT) works as an ion trap even when the electron beam is switched off. We present various experiments that exploit the ''magnetic trapping mode'' for investigations of ion confinement, charge exchange processes, atomic lifetime and ion mass measurements.

  8. Designing and building a permanent magnet Zeeman slower for calcium atoms using a 3D printer

    NASA Astrophysics Data System (ADS)

    Parsagian, Alexandria; Kleinert, Michaela

    2015-10-01

    We present the design of a Zeeman slower for calcium atoms using permanent magnets instead of more traditional electromagnets and the novel technique of 3D printing to create a very robust and flexible structure for these magnets. Zeeman slowers are ideal tools to slow atoms from several hundreds of meters per second to just a few tens of meters per second. These slower atoms can then easily be trapped in a magneto-optical trap, making Zeeman slowers a very valuable tool in many cold atom labs. The use of permanent magnets and 3D printing results in a highly stable and robust slower that is suitable for undergraduate laboratories. In our design, we arranged 28 magnet pairs, 2.0 cm apart along the axis of the slower and at varying radial distances from the axis. We determined the radial position of the magnets by simulating the combined field of all magnet pairs using Mathematica and comparing it to the ideal theoretical field for a Zeeman slower. Finally, we designed a stable, robust, compact, and easy-to-align mounting structure for the magnets in Google Sketchup, which we then printed using a commercially available 3D printer by Solidoodle. The resulting magnetic field is well suited to slow calcium atoms from the 770 m/s rms velocity at a temperature of 950 K, down to the capture velocity of the magneto-optical trap.

  9. Characterization of laser cooling in a high-magnetic-field atom trap

    NASA Astrophysics Data System (ADS)

    Paradis, E.; Zigo, S.; Hu, K. Z.; Raithel, G.

    2012-08-01

    We describe cooling and trapping of both 85Rb and 87Rb in a range of magnetic fields up to 2.6 T. Atoms are injected from a low-field pyramidal magneto-optical trap and recaptured in a high-magnetic-field atom trap. The atoms are cooled and trapped by a six-beam optical molasses via the 5S1/2|mI,mJ= 1/2>→ 5P3/2|mI,mJ= 3/2> transition (mI= 5/2 for 85Rb and mI= 3/2 for 87Rb). We study the trap fluorescence spectra, atom temperatures, density distributions, and lifetimes as a function of magnetic field and detuning parameters. The trap fluorescence spectra are both narrow and asymmetric, as is characteristic for laser cooling of atoms in an external trapping potential. The trap is modeled using a Monte Carlo trajectory simulation technique.

  10. Optical Polarization From Aligned Atoms As A Diagnostic Of Interstellar And Circumstellar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Yan, H.; Lazarian, A.

    2005-12-01

    Population among sublevels of the ground state of an atom is affected by radiative transitions induced by anisotropic radiation flux. Such aligned atoms precess in the external magnetic field and this affects properties of polarized radiation arising from both scattering and absorption by atoms. As the result the degree of light polarization depends on the direction of the magnetic field. This provides a perspective tool for studies of astrophysical magnetic fields using optical and UV polarimetry. We discuss the process of alignment that can be used to study magnetic fields in interplanetary medium, interstellar medium, circumstellar regions and quasars. To exemplify what atomic alignment can provide to the observers we consider synthetic data obtained with MHD simulations of comet wake.

  11. Resonant interaction of trapped cold atoms with a magnetic cantilever tip

    NASA Astrophysics Data System (ADS)

    Montoya, Cris; Valencia, Jose; Geraci, Andrew; Eardley, Matthew; Kitching, John

    2015-05-01

    We report the resonant coupling of laser cooled trapped Rb atoms to a micro-cantilever with a magnetic tip. An atom chip is used to trap, cool, and transport the atoms to the tip of the cantilever. The capacitively-driven cantilever oscillation produces Zeeman state transitions which result in a loss of population in the trap. In a suitably scaled setup, mechanical resonators could be used to probe and manipulate atomic spins with nanometer spatial resolution and single-spin sensitivity; this technique may enable new approaches in neutral-atom quantum computation, quantum simulation, or precision sensing.

  12. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    DOE PAGESBeta

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-24

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. Here we present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  13. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    NASA Astrophysics Data System (ADS)

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-01

    It was recently proposed that electron magnetic circular dichroism can be measured in scanning transmission electron microscopy with atomic resolution by tuning the phase distribution of an electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. We present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  14. Effects of strong magnetic fields on the electron distribution and magnetisability of rare gas atoms

    NASA Astrophysics Data System (ADS)

    Pagola, G. I.; Caputo, M. C.; Ferraro, M. B.; Lazzeretti, P.

    2004-12-01

    Strong uniform static magnetic fields compress the electronic distribution of rare gas atoms and cause a 'spindle effect', which can be illustrated by plotting charge-density functions which depend quadratically on the flux density of the applied field. The fourth rank hypermagnetisabilities of He, Ne, Ar and Kr are predicted to have small positive values. Accordingly, the diamagnetism of rare gas atoms diminishes by a very little amount in the presence of intense magnetic field.

  15. The Saga of Light-Matter Interaction and Magneto-optical Effects Applications to Atomic Magnetometry, Laser-cooled Atoms, Atomic Clocks, Geomagnetism, and Plant Bio-magnetism

    NASA Astrophysics Data System (ADS)

    Corsini, Eric P.

    The quest to expand the limited sensorial domain, in particular to bridge the inability to gauge magnetic fields near and far, has driven the fabrication of remedial tools. The interaction of ferromagnetic material with a magnetic field had been the only available technique to gauge that field for several millennium. The advent of electricity and associated classical phenomena captured in the four Maxwell equations, were a step forward. In the early 1900s, the model of quantum mechanics provided a two-way leap forward. One came from the newly understood interaction of light and matter, and more specifically the three-way coupling of photons, atoms' angular momenta, and magnetic field, which are the foundations of atomic magnetometry. The other came from magnetically sensitive quantum effects in a fabricated energy-ladder form of matter cooled to a temperature below that of the energy steps; these quantum effects gave rise to the superconducting quantum interference device (SQUID). Research using atomic magnetometers and SQUIDs has resulted in thousands of publications, text books, and conferences. The current status in each field is well described in Refs. [48,49,38,42] and all references therein. In this work we develop and investigate techniques and applications pertaining to atomic magnetometry. [Full text: eric.corsini gmail.com].

  16. A simple model for optical capture of atoms in strong magnetic quadrupole fields

    NASA Astrophysics Data System (ADS)

    Haubrich, D.; Höpe, A.; Meschede, D.

    1993-10-01

    The radiative capture of cesium atoms from the gas phase in a magnetooptic trap with strong magnetic field gradients is studied. A simplified analytic model is used to derive an upper limit for capture velocities. The resulting scaling law agrees well with the observed number of atoms and with the density as a function of field gradient.

  17. Decoherence-governed magnetic-moment dynamics of supported atomic objects

    NASA Astrophysics Data System (ADS)

    Gauyacq, Jean-Pierre; Lorente, Nicolás

    2015-11-01

    Due to the quantum evolution of molecular magnetic moments, the magnetic state of nanomagnets can suffer spontaneous changes. This process can be completely quenched by environment-induced decoherence. However, we show that for typical small supported atomic objects, the substrate-induced decoherence does change the magnetic-moment evolution but does not quell it. To be specific and to compare with experiment, we analyze the spontaneous switching between two equivalent magnetization states of atomic structures formed by Fe on Cu2N/Cu (1 0 0), measured by Loth et al (2012 Science 335 196-9). Due to the substrate-induced decoherence, the Rabi oscillations proper to quantum tunneling between magnetic states are replaced by an irreversible decay of long characteristic times leading to the observed stochastic magnetization switching. We show that the corresponding switching rates are small, rapidly decreasing with system’s size, with a 1/T thermal behavior and in good agreement with experiments. Quantum tunneling is recovered as the switching mechanism at extremely low temperatures below the μK range for a six-Fe-atom system and exponentially lower for larger atomic systems. The unexpected conclusion of this work is that experiments could detect the switching of these supported atomic systems because their magnetization evolution is somewhere between complete decoherence-induced stability and unobservably fast quantum-tunneling switching.

  18. Decoherence-governed magnetic-moment dynamics of supported atomic objects.

    PubMed

    Gauyacq, Jean-Pierre; Lorente, Nicolás

    2015-11-18

    Due to the quantum evolution of molecular magnetic moments, the magnetic state of nanomagnets can suffer spontaneous changes. This process can be completely quenched by environment-induced decoherence. However, we show that for typical small supported atomic objects, the substrate-induced decoherence does change the magnetic-moment evolution but does not quell it. To be specific and to compare with experiment, we analyze the spontaneous switching between two equivalent magnetization states of atomic structures formed by Fe on Cu2N/Cu (1 0 0), measured by Loth et al (2012 Science 335 196-9). Due to the substrate-induced decoherence, the Rabi oscillations proper to quantum tunneling between magnetic states are replaced by an irreversible decay of long characteristic times leading to the observed stochastic magnetization switching. We show that the corresponding switching rates are small, rapidly decreasing with system's size, with a 1/T thermal behavior and in good agreement with experiments. Quantum tunneling is recovered as the switching mechanism at extremely low temperatures below the μK range for a six-Fe-atom system and exponentially lower for larger atomic systems. The unexpected conclusion of this work is that experiments could detect the switching of these supported atomic systems because their magnetization evolution is somewhere between complete decoherence-induced stability and unobservably fast quantum-tunneling switching. PMID:26471260

  19. Interlayer Exchange Coupling: A General Scheme Turning Chiral Magnets into Magnetic Multilayers Carrying Atomic-Scale Skyrmions.

    PubMed

    Nandy, Ashis Kumar; Kiselev, Nikolai S; Blügel, Stefan

    2016-04-29

    We report on a general principle using interlayer exchange coupling to extend the regime of chiral magnetic films in which stable or metastable magnetic Skyrmions can appear at a zero magnetic field. We verify this concept on the basis of a first-principles model for a Mn monolayer on a W(001) substrate, a prototype chiral magnet for which the atomic-scale magnetic texture is determined by the frustration of exchange interactions, impossible to unwind by laboratory magnetic fields. By means of ab initio calculations for the Mn/W_{m}/Co_{n}/Pt/W(001) multilayer system we show that for certain thicknesses m of the W spacer and n of the Co reference layer, the effective field of the reference layer fully substitutes the required magnetic field for Skyrmion formation. PMID:27176536

  20. Interlayer Exchange Coupling: A General Scheme Turning Chiral Magnets into Magnetic Multilayers Carrying Atomic-Scale Skyrmions

    NASA Astrophysics Data System (ADS)

    Nandy, Ashis Kumar; Kiselev, Nikolai S.; Blügel, Stefan

    2016-04-01

    We report on a general principle using interlayer exchange coupling to extend the regime of chiral magnetic films in which stable or metastable magnetic Skyrmions can appear at a zero magnetic field. We verify this concept on the basis of a first-principles model for a Mn monolayer on a W(001) substrate, a prototype chiral magnet for which the atomic-scale magnetic texture is determined by the frustration of exchange interactions, impossible to unwind by laboratory magnetic fields. By means of ab initio calculations for the Mn /Wm/Con/Pt /W (001 ) multilayer system we show that for certain thicknesses m of the W spacer and n of the Co reference layer, the effective field of the reference layer fully substitutes the required magnetic field for Skyrmion formation.

  1. Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Hong, Xia; Liu, Yanmei; Li, Jun; Guo, Wei; Bai, Yubai

    2009-09-01

    Atomic force (AFM) and magnetic force microscopy (MFM) were developed to detect biomolecular specific interaction. Goat anti-mouse immunoglobulin (anti-IgG) was covalently attached onto gold substrate modified by a self-assembly monolayer of thioctic acid via 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) activation. Magnetic-labeled IgG then specifically adsorbed onto anti-IgG surface. The morphological variation was identified by AFM. MFM was proved to be a fine assistant tool to distinguish the immunorecognized nanocomposites from the impurities by detection of the magnetic signal from magnetic-labeled IgG. It would enhance the understanding of biomolecular recognition process.

  2. Reflection of a slow cesium atomic beam from a naturally magnetized Nd-Fe-B surface

    NASA Astrophysics Data System (ADS)

    Lison, F.; Haubrich, D.; Schuh, P.; Meschede, D.

    We have demonstrated the partly directed reflection of a slow cesium atomic beam by using the natural magnetic stray field above a Nd-Fe-B surface. From these experiments we determine the reflectivity and a minimum value for the magnetic stray field directly at the surface.

  3. The UKB prescription and the heavy atom effects on the nuclear magnetic shielding of vicinal heavy atoms.

    PubMed

    Maldonado, Alejandro F; Aucar, Gustavo A

    2009-07-21

    Fully relativistic calculations of NMR magnetic shielding on XYH3 (X = C, Si, Ge and Sn; Y = Br, I), XHn (n = 1-4) molecular systems and noble gases performed with a fully relativistic polarization propagator formalism at the RPA level of approach are presented. The rate of convergence (size of basis set and time involved) for calculations with both kinetic balance prescriptions, RKB and UKB, were investigated. Calculations with UKB makes it feasible to obtain reliable results for two or more heavy-atom-containing molecules. For such XYH3 systems, the influence of heavy vicinal halogen atoms on sigma(X) is such that heavy atom effects on heavy atoms (vicinal plus their own effects or HAVHA + HAHA effects) amount to 30.50% for X = Sn and Y = I; being the HAHA effect of the order of 25%. So the vicinal effect alone is of the order of 5.5%. The vicinal heavy atom effect on light atoms (HALA effect) is of the order of 28% for X = C and Y = I. A similar behaviour, but of opposite sign, is observed for sigma(Y) for which sigmaR-NR (I; X = C) (HAHA effect) is around 27% and sigmaR-NR(I; X = Sn) (HAVHA + HAHA effects) is close to 21%. Its electronic origin is paramagnetic for halogen atoms but both dia- and paramagnetic for central atoms. The effect on two bond distant hydrogen atoms is such that the largest variation of sigma(H) within the same family of XYH3 molecules appears for X = Si and Y = I: around 20%. In this case sigma(H; X = Sn, Y = I) = 33.45 ppm and sigma(H; X = Sn, Y = H) = 27.82 ppm. PMID:19842479

  4. Atomic structure and magnetic properties of Fe1-xCox alloys

    SciTech Connect

    Nguyen, Manh Cuong; Zhao, Xin; Ji, Min; Wang, Cai-Zhuang; Harmon, Bruce; Ho, Kai-Ming

    2012-03-09

    Using genetic algorithm with first-principle calculations, we searched for low-energy crystal structures of Fe1−xCox alloys. We found that Fe1−xCox alloys are highly configurationally degenerate with many additional off-stoichiometric stable structures to the well-known B2 structure. The average magnetic moment of Fe atom increases with concentration of Co in the alloy, while that of Co atom is almost constant, which are consistent with experiments and earlier studies. The magnetic moment of Fe atom is strongly dependent on the number of Co nearest neighbor and it increases with this number.

  5. Giant perpendicular magnetic anisotropy of an individual atom on two-dimensional transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Odkhuu, Dorj

    2016-08-01

    Exploring magnetism and magnetic anisotropy in otherwise nonmagnetic two-dimensional materials, such as graphene and transition metal dichalcogenides, is at the heart of spintronics research. Herein, using first-principles calculations we explore the possibility of reaching an atomic-scale perpendicular magnetic anisotropy by carefully exploring the large spin-orbit coupling, orbital magnetism, and ligand field in a suitable choice of a two-dimensional structure with transition metal adatoms. More specifically, we demonstrate perpendicular magnetic anisotropy energies up to an order of 100 meV per atom in individual ruthenium and osmium adatoms at a monosulfur vacancy in molybdenum disulfide. We further propose a phenomenological model where a spin state transition that involves hybridization between molybdenum a1 and adatomic e' orbitals is a possible mechanism for magnetization reversal from an in-plane to perpendicular orientation.

  6. Direct visualization and identification of biofunctionalized nanoparticles using a magnetic atomic force microscope.

    PubMed

    Block, Stephan; Glöckl, Gunnar; Weitschies, Werner; Helm, Christiane A

    2011-09-14

    Because of its outstanding ability to image and manipulate single molecules, atomic force microscopy (AFM) established itself as a fundamental technique in nanobiotechnology. (1) We present a new modality that distinguishes single nanoparticles by the surrounding magnetic field gradient. Diamagnetic gold and superparamagnetic iron oxide nanoparticles become discernible under ambient conditions. Images of proteins, magnetolabeled with nanoparticles, demonstrate the first steps toward a magnetic analogue to fluorescence microscopy, which combines nanoscale lateral resolution of AFM with unambiguous detection of magnetic markers. PMID:21819124

  7. Properties of the warm magnetized ISM, as inferred from WSRT polarimetric imaging

    NASA Astrophysics Data System (ADS)

    Haverkorn, M.; Katgert, P.; de Bruyn, A. G.

    2004-11-01

    We describe a first attempt to derive properties of the regular and turbulent Galactic magnetic field from multi-frequency polarimetric observations of the diffuse Galactic synchrotron background. A single-cell-size model of the thin Galactic disk is constructed which includes random and regular magnetic fields and thermal and relativistic electrons. The disk is irradiated from behind with a uniform partially polarized background. Radiation from the background and from the thin disk is Faraday rotated and depolarized while propagating through the medium. The model parameters are estimated from a comparison with 350 MHz observations in two regions at intermediate latitudes done with the Westerbork Synthesis Radio Telescope. We obtain good agreement between the estimates for the random and regular magnetic field strengths and typical scales of structure in the two regions. The regular magnetic field strength found is a few μG, and the ratio of random to regular magnetic field strength Bran/Breg is 0.7 ± 0.5, for a typical scale of the random component of 15 ± 10 pc. Furthermore, the regular magnetic field is directed almost perpendicular to the line of sight. This modeling is a potentially powerful method to estimate the structure of the Galactic magnetic field, especially when more polarimetric observations of the diffuse synchrotron background at intermediate latitudes become available.

  8. Bidirectional propagation of cold atoms in a 'stadium'-shaped magnetic guide

    SciTech Connect

    Wu Saijun; Rooijakkers, Wilbert; Striehl, Pierre; Prentiss, Mara

    2004-07-01

    We demonstrate the bidirectional propagation of more than 10{sup 7} atoms ({sup 87}Rb) around a 'stadium'-shaped magnetic ring that encloses an area of 10.9 cm{sup 2}, with a flux density exceeding 10{sup 11} atom s{sup -1} cm{sup -2}. Atoms are loaded into the guide from a two-dimensional (and higher) magneto-optical trap at one side of the 'stadium'. An optical standing wave pulse is applied to increase the propagation velocity of atoms along the waveguide. The atom sample fills the entire ring in 200 ms when counterpropagating atom sections of the original atom cloud recombine at their initial positions after a full revolution.

  9. Magnetic state selection in atomic frequency and time standards. [hydrogen masers

    NASA Technical Reports Server (NTRS)

    Peters, H. E.

    1982-01-01

    Atomic standards such as those based upon cesium and hydrogen rely upon magnetic state selection to obtain population inversion in the hyperfine transition levels. Use of new design approaches and improved magnetic materials has made it possible to fabricate improved state selectors of small size, and thus the efficiency of utilization of beam flux is greatly improved and the size and weight of the standard is reduced. The sensitivity to magnetic perturbations is also decreased, so that the accuracy and stability of the standard is improved. Several new state selector designs are illustrated and the application to standards utilizing different atomic species is analyzed.

  10. Monte Carlo simulation of a cesium atom beam in a magnetic field

    SciTech Connect

    Chen, Jiang Zhu, Hongwei; Ma, Yinguang; Li, Detian; Liu, Zhidong; Wang, Ji

    2015-03-07

    We present Monte Carlo simulations of the deflection of a beam of {sup 133}Cs atoms in a two wire magnetic field. Our results reveal the relationship between transmission rate of the atoms and incident parameters. Incident angle and position of the beam with maximum transmission are obtained from the simulations. The effect of the deflection field on the spatial distribution (beam profile) of {sup 133}Cs is derived. The method will help with the design of magnetic deflection experiments and to extract the magnetic properties from such experiments.

  11. Magnetic-field-tunable Kondo effect in alkaline-earth cold atoms

    NASA Astrophysics Data System (ADS)

    Isaev, Leonid; Rey, Ana Maria

    We study quantum magnetism and emergent Kondo physics in strongly interacting fermionic alkaline-earth atoms in an optical lattice with two Bloch bands: one localized and one itinerant. For a fully filled narrow band (two atoms per lattice site) we demonstrate that an applied magnetic field provides an efficient control of the ground state degeneracy due to the field-induced crossing of singlet and triplet state of the localized atomic pairs. We exploit this singlet-triplet resonance, as well as magnetically tunable interactions of atoms in different electronic states via the recently-discovered inter-orbital Feshbach resonance, and demonstrate that the system exhibits a magnetic field-induced Kondo phase characterized by delocalization of local singlets and a large Fermi surface. We also determine the phase diagram of the system within an effective low-energy model that incorporates the above magnetic-field effect as well as atomic interactions in the two optical lattice bands. Our results can be tested with ultracold 173 Yb , and provide a model for the magnetic field-induced heavy-fermion state in filled skutterudites such as PrOs4Sb12 . This work was supported by the NSF (PIF-1211914 and PFC-1125844), AFOSR, AFOSR-MURI, NIST and ARO individual investigator awards.

  12. Cooling by Spontaneous Decay of Highly Excited Antihydrogen Atoms in Magnetic Traps

    SciTech Connect

    Pohl, T.; Sadeghpour, H. R.; Nagata, Y.; Yamazaki, Y.

    2006-11-24

    An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen (H) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of H atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of H magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of H confined in a cusp trap is shown to depend as {approx}2.2T{sub n{sub 0}}n{sub 0}{sup -2/3} on the initial Rydberg level n{sub 0} and temperature T{sub n{sub 0}}.

  13. Precisely mapping the magnetic field gradient in vacuum with an atom interferometer

    SciTech Connect

    Zhou Minkang; Hu Zhongkun; Duan Xiaochun; Sun Buliang; Zhao Jinbo; Luo Jun

    2010-12-15

    The magnetic field gradient has been measured with an atom interferometer using the magnetic sublevels of {sup 87}Rb atoms. The Doppler-insensitive measurement effectively eliminates the contribution from gravity and background vibration noise, and the differential measurement also can reject some systematic errors. A resolution of 300 pT/mm has been demonstrated with a 90-s integration time and a spatial resolution of 1.4 mm. The gradiometer was then used to measure the magnetic field gradient in an ultrahigh-vacuum environment. The technique will also be very useful to subtract the systematic error arising from the magnetic field inhomogeneity in precision atom-interferometry experiments, such as gravity measurement.

  14. Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Shi, Jun-Jie

    2014-01-01

    The electronic structure and magnetic properties of the transition-metal (TM) atoms (Sc—Zn, Pt and Au) doped zigzag GaN single-walled nanotubes (NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6-16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Co-doped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.

  15. Atomic structure, alloying behavior, and magnetism in small Fe-Pt clusters

    NASA Astrophysics Data System (ADS)

    Chittari, Bheema Lingam; Kumar, Vijay

    2015-09-01

    We report results of the atomic structure, alloying behavior, and magnetism in F emP tn(m +n =2 -10 ) clusters using projector augmented wave (PAW) pseudopotential method and spin-polarized generalized gradient approximation (GGA) for the exchange-correlation energy. These results are compared with those obtained by using HCTH exchange-correlation functional and LANL2DZ basis set in the Gaussian program and the overall trends are found to be similar. As in bulk Fe-Pt alloys, clusters with equal composition of Fe and Pt have the largest binding energy and the largest heat of nanoalloy formation for a given number of atoms in the cluster. There are some deviations due to the different symmetries in clusters and in cases where the total number of atoms is odd. The lowest energy isomers tend to maximize bonds between unlike atoms with Fe (Pt) atoms occupying high (low) coordination sites in the core (surface) of the cluster. The binding energy, heat of formation, and the second order difference of the total energy show F e2P t2 , F e4P t4 , and F e4P t6 clusters to be the most stable ones among the different clusters we have studied. The magnetic moments on Fe atoms are high in Pt-rich clusters as well as in small Fe-rich clusters and decrease as the aggregation of Fe atoms and the cluster size increases. The maximum value of the magnetic moments on Fe atoms is ˜3.8 μB , whereas for Pt atoms it is 1 μB. These are quite high compared with the values for bulk Fe as well as bulk FePt and F e3Pt phases while bulk Pt is nonmagnetic. There is significant charge transfer from those Fe atoms that interact directly with Pt atoms. We discuss the hybridization between the electronic states of Pt and Fe atoms as well as the variation in the magnetic moments on Fe and Pt atoms. Our results provide insight into the understanding of the nanoalloy behavior of Fe-Pt and we hope that this would help to design Fe based nanoalloys and their assemblies with high magnetic moments for

  16. Magnetic merging of ultracold atomic gases of {sup 85}Rb and {sup 87}Rb

    SciTech Connect

    Haendel, S.; Wiles, T. P.; Marchant, A. L.; Hopkins, S. A.; Adams, C. S.; Cornish, S. L.

    2011-05-15

    We report the magnetic merging of ultracold atomic gases of {sup 85}Rb and {sup 87}Rb by the controlled overlap of two initially spatially separated magnetic traps. We present a detailed analysis of the combined magnetic-field potential as the two traps are brought together that predicts a clear optimum trajectory for the merging. We verify this prediction experimentally using {sup 85}Rb and find that the final atom number in the merged trap is maximized with minimal heating by following the predicted optimum trajectory. Using the magnetic-merging approach allows us to create variable-ratio isotopic Rb mixtures with a single laser-cooling setup by simply storing one isotope in a magnetic trap before jumping the laser frequencies to the transitions necessary to laser cool the second isotope.

  17. An architecture for quantum computation with magnetically trapped Holmium atoms

    NASA Astrophysics Data System (ADS)

    Saffman, Mark; Hostetter, James; Booth, Donald; Collett, Jeffrey

    2016-05-01

    Outstanding challenges for scalable neutral atom quantum computation include correction of atom loss due to collisions with untrapped background gas, reduction of crosstalk during state preparation and measurement due to scattering of near resonant light, and the need to improve quantum gate fidelity. We present a scalable architecture based on loading single Holmium atoms into an array of Ioffe-Pritchard traps. The traps are formed by grids of superconducting wires giving a trap array with 40 μm period, suitable for entanglement via long range Rydberg gates. The states | F = 5 , M = 5 > and | F = 7 , M = 7 > provide a magic trapping condition at a low field of 3.5 G for long coherence time qubit encoding. The F = 11 level will be used for state preparation and measurement. The availability of different states for encoding, gate operations, and measurement, spectroscopically isolates the different operations and will prevent crosstalk to neighboring qubits. Operation in a cryogenic environment with ultra low pressure will increase atom lifetime and Rydberg gate fidelity by reduction of blackbody induced Rydberg decay. We will present a complete description of the architecture including estimates of achievable performance metrics. Work supported by NSF award PHY-1404357.

  18. Electronic and magnetic properties of nonmetal atoms adsorbed ReS{sub 2} monolayers

    SciTech Connect

    Zhang, Xiaoou; Li, Qingfang

    2015-08-14

    The stable configurations and electronic and magnetic properties of nonmetal atoms (H, N, P, O, S, F, and Cl) adsorbed ReS{sub 2} monolayers have been investigated by first-principles calculations. It is found that H, O, S, F, and Cl prefer to occupy the peak sites of S atoms, while both N and P atoms favor the valley sites of S atoms. The ReS{sub 2} sheet exhibits a good adsorption capability to nonmetal atoms. The reconstruction of the surface is pronounced in N- and P-adsorbed ReS{sub 2} monolayers. In H-adsorbed case, the Fermi level is pulled into the conduction band, which results in the semiconductor-metal transition. The same magnetic moment of 1μ{sub B} is found in the N-, P-, F-, and Cl-adsorbed ReS{sub 2} monolayers, while the mechanisms of forming magnetic moment for N (P)- and F (Cl)-adsorbed cases are different. In addition, the spatial extensions of spin density in P-, F-, and Cl-adsorbed cases are larger than that in N-adsorbed case, which is more suitable to achieve long-range magnetic coupling interaction at low defect concentrations. Our results provide insight for achieving metal-free magnetism and a tunable band gap for various electronic and spintronic devices based on ReS{sub 2}.

  19. Electronic structures and magnetic properties of rare-earth-atom-doped BNNTs

    NASA Astrophysics Data System (ADS)

    Ren, Juan; Zhang, Ning-Chao; Wang, Peng; Ning, Chao; Zhang, Hong; Peng, Xiao-Juan

    2016-04-01

    Stable geometries, electronic structures, and magnetic properties of (8,0) and (4,4) single-walled BN nanotubes (BNNTs) doped with rare-earth (RE) atoms are investigated using the first-principles pseudopotential plane wave method with density functional theory (DFT). The results show that these RE atoms can be effectively doped in BNNTs with favorable energies. Because of the curvature effect, the values of binding energy for RE-atom-doped (4,4) BNNTs are larger than those of the same atoms on (8,0) BNNTs. Electron transfer between RE-5 d, 6 s, and B-2 p, N-2 p orbitals was also observed. Furthermore, electronic structures and magnetic properties of BNNTs can be modified by such doping. The results show that the adsorption of Ce, Pm, Sm, and Eu atoms can induce magnetization, while no magnetism is observed when BNNTs are doped with La. These results are useful for spintronics applications and for developing magnetic nanostructures.

  20. Structure of magnetic resonance in 87Rb atoms

    NASA Astrophysics Data System (ADS)

    Kozlov, A. N.; Zibrov, S. A.; Zibrov, A. A.; Yudin, V. I.; Taichenachev, A. V.; Yakovlev, V. P.; Tsygankov, E. A.; Zibrov, A. S.; Vassiliev, V. V.; Velichansky, V. L.

    2016-05-01

    Magnetic resonance at the F g = 1 rightleftarrows F e = 1 transition of the D 1 line in 87Rb has been studied with pumping and detection by linearly polarized radiation and detection at the double frequency of the radiofrequency field. The intervals of allowed values of the static and alternating magnetic fields in which magnetic resonance has a single maximum have been found. The structure appearing beyond these intervals has been explained. It has been shown that the quadratic Zeeman shift is responsible for the three-peak structure of resonance; the radiofrequency shift results in the appearance of additional extrema in resonance, which can be used to determine the relaxation constant Γ2. The possibility of application in magnetometry has been discussed.

  1. Wireless power transfer based on magnetic metamaterials consisting of assembled ultra-subwavelength meta-atoms

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Li, Y. H.; Gao, N.; Yang, F.; Chen, Y. Q.; Fang, K.; Zhang, Y. W.; Chen, H.

    2015-03-01

    In this letter, a potential way to transfer power wirelessly based on magnetic metamaterials (MMs) assembled by ultra-subwavelength meta-atoms is proposed. Frequency-domain simulation and experiments are performed for accurately obtaining effective permeability of magnetic metamaterials. The results demonstrate that MMs possess great power for enhancing the wireless power transfer efficiency between two non-resonant coils. Further investigations on the magnetic-field distribution demonstrate that a large-area flattened magnetic field in near range can be effectively realized, exhibiting great flexibility in assembling.

  2. Realizing exactly solvable SU (N ) magnets with thermal atoms

    NASA Astrophysics Data System (ADS)

    Beverland, Michael E.; Alagic, Gorjan; Martin, Michael J.; Koller, Andrew P.; Rey, Ana M.; Gorshkov, Alexey V.

    2016-05-01

    We show that n thermal fermionic alkaline-earth-metal atoms in a flat-bottom trap allow one to robustly implement a spin model displaying two symmetries: the Sn symmetry that permutes atoms occupying different vibrational levels of the trap and the SU (N ) symmetry associated with N nuclear spin states. The symmetries make the model exactly solvable, which, in turn, enables the analytic study of dynamical processes such as spin diffusion in this SU (N ) system. We also show how to use this system to generate entangled states that allow for Heisenberg-limited metrology. This highly symmetric spin model should be experimentally realizable even when the vibrational levels are occupied according to a high-temperature thermal or an arbitrary nonthermal distribution.

  3. Excitation of simple atoms by slow magnetic monopoles

    SciTech Connect

    Kroll, N.M.; Parke, S.J.; Ganapathi, V.; Drell, S.D.

    1984-01-01

    We present a theory of excitation of simple atoms by slow moving massive monopoles. Previously presented results for a monopole of Dirac strength on hydrogen and helium are reviewed. The hydrogen theory is extended to include arbitrary integral multiples of the Dirac pole strength. The excitation of helium by double strength poles and by dyons is also discussed. It is concluded that a helium proportional counter is a reliable and effective detector for monopoles of arbitrary strength, and for negatively charged dyons.

  4. Ultra-sensitive Magnetic Microscopy with an Atomic Magnetometer

    SciTech Connect

    Kim, Young Jin

    2015-08-19

    The PowerPoint presentation focused on research goals, specific information about the atomic magnetometer, response and resolution factors of the SERF magnetometer, FC+AM systems, tests of field transfer and resolution on FC, gradient cancellation, testing of AM performance, ideas for a multi-channel AM, including preliminary sensitivity testing, and a description of a 6 channel DAQ system. A few ideas for future work ended the presentation.

  5. Atomic-Scale Interfacial Magnetism in Fe/Graphene Heterojunction

    PubMed Central

    Liu, W. Q.; Wang, W. Y.; Wang, J. J.; Wang, F. Q.; Lu, C.; Jin, F.; Zhang, A.; Zhang, Q. M.; Laan, G. van der; Xu, Y. B.; Li, Q. X.; Zhang, R.

    2015-01-01

    Successful spin injection into graphene makes it a competitive contender in the race to become a key material for quantum computation, or the spin-operation-based data processing and sensing. Engineering ferromagnetic metal (FM)/graphene heterojunctions is one of the most promising avenues to realise it, however, their interface magnetism remains an open question up to this day. In any proposed FM/graphene spintronic devices, the best opportunity for spin transport could only be achieved where no magnetic dead layer exists at the FM/graphene interface. Here we present a comprehensive study of the epitaxial Fe/graphene interface by means of X-ray magnetic circular dichroism (XMCD) and density functional theory (DFT) calculations. The experiment has been performed using a specially designed FM1/FM2/graphene structure that to a large extent restores the realistic case of the proposed graphene-based transistors. We have quantitatively observed a reduced but still sizable magnetic moments of the epitaxial Fe ML on graphene, which is well resembled by simulations and can be attributed to the strong hybridization between the Fe 3dz2 and the C 2pz orbitals and the sp-orbital-like behavior of the Fe 3d electrons due to the presence of graphene. PMID:26145155

  6. Coupled-cluster theory for atoms and molecules in strong magnetic fields.

    PubMed

    Stopkowicz, Stella; Gauss, Jürgen; Lange, Kai K; Tellgren, Erik I; Helgaker, Trygve

    2015-08-21

    An implementation of coupled-cluster (CC) theory to treat atoms and molecules in finite magnetic fields is presented. The main challenges for the implementation stem from the magnetic-field dependence in the Hamiltonian, or, more precisely, the appearance of the angular momentum operator, due to which the wave function becomes complex and which introduces a gauge-origin dependence. For this reason, an implementation of a complex CC code is required together with the use of gauge-including atomic orbitals to ensure gauge-origin independence. Results of coupled-cluster singles-doubles-perturbative-triples (CCSD(T)) calculations are presented for atoms and molecules with a focus on the dependence of correlation and binding energies on the magnetic field. PMID:26298118

  7. Magnetic-field-mediated hybridization of ultracold atoms and a nanostring

    NASA Astrophysics Data System (ADS)

    Tretiakov, Andrei; Saglamyurek, Erhan; Leblanc, Lindsay

    2016-05-01

    Through nanofabrication, mechanical elements can be engineered with vibration frequencies near the hyperfine and Zeeman resonances in an atomic system. By including magnetic elements as part of this mechanical object, we can couple the vibrational modes of the oscillator to the spin states of the atoms. The nanostring design offers new options for creating magnetic fields using dc and ac currents. Here, we consider and compare different ways to provide magnetic coupling between this mechanical motion and the spin states of an ultracold 87 Rb gas, and discuss methods of manipulating the quantum state of a mechanical oscillator using cold atoms, such as mechanical cooling. Finally, we discuss our progress towards the experimental realization of this system, including a system for optically transferring at cold 87 Rb gas from a remote 3D MOT, and constructing a versatile load-lock type UHV system for rapidly prototyping new devices.

  8. Coupled-cluster theory for atoms and molecules in strong magnetic fields

    SciTech Connect

    Stopkowicz, Stella Lange, Kai K.; Tellgren, Erik I.; Helgaker, Trygve; Gauss, Jürgen

    2015-08-21

    An implementation of coupled-cluster (CC) theory to treat atoms and molecules in finite magnetic fields is presented. The main challenges for the implementation stem from the magnetic-field dependence in the Hamiltonian, or, more precisely, the appearance of the angular momentum operator, due to which the wave function becomes complex and which introduces a gauge-origin dependence. For this reason, an implementation of a complex CC code is required together with the use of gauge-including atomic orbitals to ensure gauge-origin independence. Results of coupled-cluster singles–doubles–perturbative-triples (CCSD(T)) calculations are presented for atoms and molecules with a focus on the dependence of correlation and binding energies on the magnetic field.

  9. Automatic compensation of magnetic field for a rubidium space cold atom clock

    NASA Astrophysics Data System (ADS)

    Lin, Li; Jingwei, Ji; Wei, Ren; Xin, Zhao; Xiangkai, Peng; Jingfeng, Xiang; Desheng, Lü; Liang, Liu

    2016-07-01

    When the cold atom clock operates in microgravity around the near-earth orbit, its performance will be affected by the fluctuation of magnetic field. A strategy is proposed to suppress the fluctuation of magnetic field by additional coils, whose current is changed accordingly to compensate the magnetic fluctuation by the linear and incremental compensation. The flight model of the cold atom clock is tested in a simulated orbital magnetic environment and the magnetic field fluctuation in the Ramsey cavity is reduced from 17 nT to 2 nT, which implied the uncertainty due to the second order Zeeman shift is reduced to be less than 2×10‑16. In addition, utilizing the compensation, the magnetic field in the trapping zone can be suppressed from 7.5 μT to less than 0.3 μT to meet the magnetic field requirement of polarization gradients cooling of atoms. Project supported by the Ministry of Science and Technology of China (Grant No. 2013YQ09094304), the Youth Innovation Promotion Association, Chinese Academy of Sciences, and the National Natural Science Foundation of China (Grant Nos. 11034008 and 11274324).

  10. Control of light trapping in a large atomic system by a static magnetic field

    NASA Astrophysics Data System (ADS)

    Skipetrov, S. E.; Sokolov, I. M.; Havey, M. D.

    2016-07-01

    We propose to control light trapping in a large ensemble of cold atoms by an external, static magnetic field. For an appropriate choice of frequency and polarization of the exciting pulse, the field is expected to speed up the fluorescence of a dilute atomic system. In a dense ensemble, the field does not affect the early-time superradiant signal but amplifies intensity oscillations at intermediate times and induces a very slow, nonexponential long-time decay. The slowing down of fluorescence is due to the excitation of spatially localized collective atomic states that appear only under a strong magnetic field and have exponentially long lifetimes. Our results therefore pave a way towards experimental observation of the disorder-induced localization of light in cold atomic systems.

  11. Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms

    SciTech Connect

    Leung, V. Y. F.; Pijn, D. R. M.; Schlatter, H.; Torralbo-Campo, L.; La Rooij, A. L.; Mulder, G. B.; Naber, J.; Soudijn, M. L.; Tauschinsky, A.; Spreeuw, R. J. C.; Abarbanel, C.; Hadad, B.; Golan, E.; Folman, R.

    2014-05-15

    We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold {sup 87}Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation.

  12. Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms.

    PubMed

    Leung, V Y F; Pijn, D R M; Schlatter, H; Torralbo-Campo, L; La Rooij, A L; Mulder, G B; Naber, J; Soudijn, M L; Tauschinsky, A; Abarbanel, C; Hadad, B; Golan, E; Folman, R; Spreeuw, R J C

    2014-05-01

    We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold (87)Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation. PMID:24880348

  13. Magnetic-field-tunable Kondo effect in alkaline-earth cold atoms

    NASA Astrophysics Data System (ADS)

    Isaev, Leonid; Rey, Ana Maria

    2015-05-01

    We study quantum magnetism in strongly interacting fermionic alkaline-earth atoms (AEAs). Due to the decoupling of electronic and nuclear degrees of freedom, AEAs in two lowest electronic states (1S0 and 3P0) obey an accurate SU(N 2 I + 1) symmetry in their two-body collisions (I is the nuclear spin). We consider a system that realizes the simplest SU(2) case (for atoms prepared in two nuclear-spin states) in an optical lattice with two bands: one localized and one itinerant. For the fully filled narrow band (two atoms per lattice site) we demonstrate that an applied magnetic field provides an efficient control of the local ground state degeneracy due to mixing of spin and orbital two-body states. We derive an effective low-energy model that includes this magnetic-field effect as well as atomic interactions in the two optical lattice bands, and show that it exhibits a peculiar phenomenon of a magnetic field-induced Kondo effect, so far observed only in Coulomb blockaded quantum dots. We expect that our results can be tested with ultracold 173 Yb or 87 Sr atoms. Supported by JILA-NSF-PFC-1125844, NSF-PIF-1211914, ARO, AFOSR, AFOSR-MURI.

  14. An atomic coilgun: using pulsed magnetic fields to slow a supersonic beam

    NASA Astrophysics Data System (ADS)

    Narevicius, E.; Parthey, C. G.; Libson, A.; Narevicius, J.; Chavez, I.; Even, U.; Raizen, M. G.

    2007-10-01

    We report the experimental demonstration of a novel method to slow atoms and molecules with permanent magnetic moments using pulsed magnetic fields. In our experiments, we observe the slowing of a supersonic beam of metastable neon from 461.0 ± 7.7 to 403 ± 16 m s-1 in 18 stages, where the slowed peak is clearly separated from the initial distribution. This method has broad applications as it may easily be generalized, using seeding and entrainment into supersonic beams, to all paramagnetic atoms and molecules.

  15. Density-functional-theory calculations of matter in strong magnetic fields. I. Atoms and molecules

    SciTech Connect

    Medin, Zach; Lai Dong

    2006-12-15

    We present calculations of the electronic structure of various atoms and molecules in strong magnetic fields ranging from B=10{sup 12} G to 2x10{sup 15} G, appropriate for radio pulsars and magnetars. For these field strengths, the magnetic forces on the electrons dominate over the Coulomb forces, and to a good approximation the electrons are confined to the ground Landau level. Our calculations are based on the density functional theory, and use a local magnetic exchange-correlation function which is tested to be reliable in the strong field regime. Numerical results of the ground-state energies are given for H{sub N} (up to N=10), He{sub N} (up to N=8), C{sub N} (up to N=5), and Fe{sub N} (up to N=3), as well as for various ionized atoms. Fitting formulae for the B dependence of the energies are also given. In general, as N increases, the binding energy per atom in a molecule, vertical bar E{sub N}|/N, increases and approaches a constant value. For all the field strengths considered in this paper, hydrogen, helium, and carbon molecules are found to be bound relative to individual atoms (although for B less than a few x10{sup 12} G, carbon molecules are very weakly bound relative to individual atoms). Iron molecules are not bound at B < or approx. 10{sup 13} G, but become energetically more favorable than individual atoms at larger field strengths.

  16. Microrheology of cells with magnetic force modulation atomic force microscopy.

    PubMed

    Rebêlo, L M; de Sousa, J S; Mendes Filho, J; Schäpe, J; Doschke, H; Radmacher, M

    2014-04-01

    We propose a magnetic force modulation method to measure the stiffness and viscosity of living cells using a modified AFM apparatus. An oscillating magnetic field makes a magnetic cantilever oscillate in contact with the sample, producing a small AC indentation. By comparing the amplitude of the free cantilever motion (A0) with the motion of the cantilever in contact with the sample (A1), we determine the sample stiffness and viscosity. To test the method, the frequency-dependent stiffness of 3T3 fibroblasts was determined as a power law k(s)(f) = α + β(f/f¯)(γ) (α = 7.6 × 10(-4) N m(-1), β = 1.0 × 10(-4) N m(-1), f¯ = 1 Hz, γ = 0.6), where the coefficient γ = 0.6 is in good agreement with rheological data of actin solutions with concentrations similar to those in cells. The method also allows estimation of the internal friction of the cells. In particular we found an average damping coefficient of 75.1 μN s m(-1) for indentation depths ranging between 1.0 μm and 2.0 μm. PMID:24651941

  17. Twilight Observations of Thermospheric Atomic Oxygen Density during Magnetic Storms

    NASA Astrophysics Data System (ADS)

    Rogan, T.; Meriwether, J. W.; Brown, L. B.

    2005-12-01

    Fabry-Perot interferometer (FPI) observations of the 732-nm doublet emission during evening and morning twilights have been made regularly at Arequipa, Peru (16.5 S, 71.4 W) since April, 2005. Arequipa is a site located 4 degrees south of the magnetic equator. Excitation of this emission is a result of the EUV photoionization of [O] to generate the 2P metastable state of O+. Variation of this emission intensity during twilight occurs as the twilight terminator passes through the thermosphere during evening or morning twilights. Consequently, the 732-nm emission intensity is proportional to the [O] abundance illuminated by the Sun along the line-of-sight path from the Arequipa FPI through the thermosphere. Contamination of the FPI spectra by OH mesospheric emissons does appear but can be treated by appropriate scaling and subtraction of the OH emission spectrum. These twilight profiles can be compared with model predictions based upon the MSIS-00 empirical model, and absolute thermospheric [O] densities can be retrieved by comparison with the model predictions. Examination of these twilight profiles during periods of magnetic storm activity will show how the thermospheric [O] density responds to the initiation and recovery of the magnetic storm, and several examples of such behavior will be presented.

  18. Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

    NASA Astrophysics Data System (ADS)

    Huang, Xu-Guang

    2016-02-01

    The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects.

  19. Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases.

    PubMed

    Huang, Xu-Guang

    2016-01-01

    The chiral magnetic and chiral separation effects-quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma-have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

  20. Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

    PubMed Central

    Huang, Xu-Guang

    2016-01-01

    The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

  1. The response of thermospheric atomic nitrogen to magnetic storms

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Mauersberger, K.

    1983-01-01

    Neutral composition data obtained by the open-source neutral-mass spectrometer on the polar orbiting Atmosphere Explorer D satellite during the periods October 31 to November 15, 1975, and January 5 to 15, 1976, are used to characterize the response of thermospheric atomic nitrogen densities to geomagnetic activity. These periods provided nearly simultaneous polar and low-latitude data coverage. At low and middle latitudes near dawn and at all latitudes on the dayside, N densities at 400 km appear to vary like those of a species of atomic mass 14: N is observed to increase with increasing geomagnetic activity in a manner similar to that of O. At auroral latitudes near dawn, however, there is a more complex dependence on the amplitude of the disturbance. For substorm-scale activity, N tends to increase during periods of auroral heating but exhibits a sharp temporary decrease afterward. During large storms there is a significant but short-lived increase of N at auroral latitudes. The present results support current models showing that N is produced and transported out of the auroral zone during geomagnetic disturbances.

  2. Magnetic-sublevel-independent magic wavelengths: Application to Rb and Cs atoms

    NASA Astrophysics Data System (ADS)

    Singh, Sukhjit; Sahoo, B. K.; Arora, Bindiya

    2016-06-01

    A generic scheme to trap atoms at the magic wavelengths λmagic that are independent of vector and tensor components of the interactions of the atoms with the external electric field is presented. The λmagic for the laser cooling D2 lines in the Rb and Cs atoms are demonstrated and their corresponding polarizability values without vector and tensor contributions are given. Consequently, these λmagic are independent of magnetic sublevels and hyperfine levels of the atomic states involved in the transition, thus, they can offer unique approaches to carrying out many high-precision measurements with minimal systematics. Inevitably, the proposed technique can also be used for electronic or hyperfine transitions in other atomic systems.

  3. Optical lattice polarization effects on magnetically induced optical atomic clock transitions

    SciTech Connect

    Taichenachev, A. V.; Yudin, V. I.; Oates, C. W.

    2007-08-15

    We derive the frequency shift for a forbidden optical transition J=0{yields}J{sup '}=0 caused by the simultaneous actions of an elliptically polarized lattice field and a static magnetic field. We find that a simple configuration of lattice and magnetic fields leads to a cancellation of this shift to first order in lattice intensity and magnetic field. In this geometry, the second-order lattice intensity shift can be minimized as well by use of optimal lattice polarization. Suppression of these shifts could considerably enhance the performance of the next generation of atomic clocks.

  4. Electronic and magnetic properties of nonmetal atoms doped blue phosphorene: First-principles study

    NASA Astrophysics Data System (ADS)

    Zheng, Huiling; Yang, Hui; Wang, Hongxia; Du, Xiaobo; Yan, Yu

    2016-06-01

    Using first-principles calculations, we study the geometrical structure, electronic structure and magnetic properties of substitutionally doped blue phosphorene with a series of nonmetallic atoms, including F, Cl, B, N, C, Si and O. The calculated formation energies and molecular dynamics simulations indicate that F, Cl, B, N, C, Si and O doped blue phosphorene are stable. Moreover, the substitutional doping of F, Cl, B and N cannot induce the magnetism in blue phosphorene due to the saturation or pairing of the valence electron of dopant and its neighboring P atoms. In contrast, ground states of C, Si and O doped blue phosphorene are spin-polarized and the magnetic moments induced by a doping atom are all 1.0 μB, which is attributed to the appearance of an unpaired valence electron of C and Si and the formation of a nonbonding 3p electron of a neighboring P atom around O. Furthermore, the magnetic coupling between the moments induced by two C, Si and O are found to be long-range anti-ferromagnetic and the origin of the coupling can be attributed to the p-p hybridization interaction involving polarized electrons.

  5. Irregular wave functions of a hydrogen atom in a uniform magnetic field

    NASA Technical Reports Server (NTRS)

    Wintgen, D.; Hoenig, A.

    1989-01-01

    The highly excited irregular wave functions of a hydrogen atom in a uniform magnetic field are investigated analytically, with wave function scarring by periodic orbits considered quantitatively. The results obtained confirm that the contributions of closed classical orbits to the spatial wave functions vanish in the semiclassical limit. Their disappearance, however, is slow. This discussion is illustrated by numerical examples.

  6. Atomic Scale Study of Interfaces Involved in Epitaxial Fe/MgO/Fe Magnetic Tunnel Junctions

    SciTech Connect

    Andrieu, S.; Serra, R.; Bonell, F.; Tiusan, C.; Calmels, L.; Snoeck, E.; Varela del Arco, Maria; Pennycook, Stephen J; Walls, M.; Colliex, C.

    2009-01-01

    Epitaxial Fe/MgO/Fe(001) magnetic tunnel junctions grown by Molecular Beam Epitaxy have been studied by using spatially resolved Electron Energy Loss Spectroscopy (EELS). The structure, the chemical composition as well as the bonding variations across the interfaces were investigated up to the atomic scale.

  7. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    PubMed Central

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  8. Irregular wave functions of a hydrogen atom in a uniform magnetic field

    SciTech Connect

    Wintgen, D. Max-Planck-Institut fuer Kernphysik, Postfach 103980, D-6900 Heidelberg, ); Honig, A. )

    1989-10-02

    We study the irregular wave functions of a highly excited hydrogen atom in a uniform magnetic field. The scarring of wave functions by periodic orbits is quantitatively investigated. The shape of unperturbed scars is in good agreement with recent semiclassical predictions.

  9. Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field

    NASA Astrophysics Data System (ADS)

    Afrousheh, Kourosh; Bohlouli-Zanjani, Parisa; Carter, Jeffery; Mugford, Ashton; Martin, James D. D.

    2006-05-01

    Laser cooled Rb atoms were optically excited to 46d5/2 Rydberg states. A microwave pulse transferred a fraction of the atoms to the 47p3/2 Rydberg state. The resonant electric dipole-dipole interactions between atoms in these two states were probed using the linewidth of the two-photon microwave transitions 46d5/2 -- 47d5/2. The presence of a weak magnetic field (roughly 1 G) reduced the observed line broadening, indicating that the interaction is suppressed by the field. The field removes some of the energy degeneracies responsible foe the resonant interaction, and this is the basis for a quantitative model of the resulting suppression. A technique for the calibration of magnetic field strengths using the 34s1/2 -- 34p1/2 one-photon transition is also presented.

  10. Resonant electric dipole-dipole interactions between cold Rydberg atoms in a magnetic field

    NASA Astrophysics Data System (ADS)

    Afrousheh, K.; Bohlouli-Zanjani, P.; Carter, J. D.; Mugford, A.; Martin, J. D. D.

    2006-06-01

    Laser-cooled Rb85 atoms were optically excited to 46d5/2 Rydberg states. A microwave pulse transferred a fraction of the atoms to the 47p3/2 Rydberg state. The resonant electric dipole-dipole interactions between atoms in these two states were probed using the linewidth of the two-photon microwave transition 46d5/2-47d5/2 . The presence of a weak magnetic field ≈0.5G reduced the observed line broadening, indicating that the interaction is suppressed by the field. The field removes some of the energy degeneracies responsible for the resonant interaction, and this is the basis for a quantitative model of the resulting suppression. A technique for the calibration of magnetic field strengths using the 34s1/2-34p1/2 one-photon transition is also presented.

  11. Photoionization microscopy for a hydrogen atom in parallel electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Deng, M.; Gao, W.; Lu, Rong; Delos, J. B.; You, L.; Liu, H. P.

    2016-06-01

    In photoionization microscopy experiments, an atom is placed in static external fields, it is ionized by a laser, and an electron falls onto a position-sensitive detector. The current of electrons arriving at various points on the detector depends upon the initial state of the atom, the excited states to which the electron is resonantly or nonresonantly excited, and the various paths leading from the atom to the final point on the detector. We report here quantum-mechanical computations of photoionization microscopy in parallel electric and magnetic fields. We focus especially on the patterns resulting from resonant excited states. We show that the magnetic field substantially modifies some of these resonant states, confining them in the radial direction, and that it has a strong effect on the interference pattern at the detector.

  12. Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

    NASA Astrophysics Data System (ADS)

    Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

    2015-05-01

    A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

  13. Spectroscopic Studies of Atomic and Molecular Processes in the Edge Region of Magnetically Confined Fusion Plasmas

    SciTech Connect

    Hey, J. D.; Brezinsek, S.; Mertens, Ph.; Unterberg, B.

    2006-12-01

    Edge plasma studies are of vital importance for understanding plasma-wall interactions in magnetically confined fusion devices. These interactions determine the transport of neutrals into the plasma, and the properties of the plasma discharge. This presentation deals with optical spectroscopic studies of the plasma boundary, and their role in elucidating the prevailing physical conditions. Recorded spectra are of four types: emission spectra of ions and atoms, produced by electron impact excitation and by charge-exchange recombination, atomic spectra arising from electron impact-induced molecular dissociation and ionisation, visible spectra of molecular hydrogen and its isotopic combinations, and laser-induced fluorescence (LIF) spectra. The atomic spectra are strongly influenced by the confining magnetic field (Zeeman and Paschen-Back effects), which produces characteristic features useful for species identification, temperature determination by Doppler broadening, and studies of chemical and physical sputtering. Detailed analysis of the Zeeman components in both optical and LIF spectra shows that atomic hydrogen is produced in various velocity classes, some related to the relevant molecular Franck-Condon energies. The latter reflect the dominant electron collision processes responsible for production of atoms from molecules. This assignment has been verified by gas-puffing experiments through special test limiters. The higher-energy flanks of hydrogen line profiles probably also show the influence of charge-exchange reactions with molecular ions accelerated in the plasma sheath ('scrape-off layer') separating limiter surfaces from the edge plasma, in analogy to acceleration in the cathode-fall region of gas discharges. While electron collisions play a vital role in generating the spectra, ion collisions with excited atomic radiators act through re-distribution of population among the atomic fine-structure sublevels, and momentum transfer to the atomic nuclei via

  14. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-02-01

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features.

  15. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy.

    PubMed

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-01-01

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features. PMID:26852801

  16. Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy

    PubMed Central

    Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

    2016-01-01

    Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features. PMID:26852801

  17. Detecting the magnetic response of iron oxide capped organosilane nanostructures using magnetic sample modulation and atomic force microscopy.

    PubMed

    Li, Jie-Ren; Lewandowski, Brian R; Xu, Song; Garno, Jayne C

    2009-06-15

    A new imaging strategy using atomic force microscopy (AFM) is demonstrated for mapping magnetic domains at size regimes below 100 nm. The AFM-based imaging mode is referred to as magnetic sample modulation (MSM), since the flux of an AC-generated electromagnetic field is used to induce physical movement of magnetic nanomaterials on surfaces during imaging. The AFM is operated in contact mode using a soft, nonmagnetic tip to detect the physical motion of the sample. By slowly scanning an AFM probe across a vibrating area of the sample, the frequency and amplitude of vibration induced by the magnetic field is tracked by changes in tip deflection. Thus, the AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. Essentially, MSM is a hybrid of contact mode AFM combined with selective modulation of magnetic domains. The positional feedback loop for MSM imaging is the same as that used for force modulation and contact mode AFM; however, the vibration of the sample is analyzed using channels of a lock-in amplifier. The investigations are facilitated by nanofabrication methods combining particle lithography with organic vapor deposition and electroless deposition of iron oxide, to prepare designed test platforms of magnetic materials at nanometer length scales. Custom test platforms furnished suitable surfaces for MSM characterizations at the level of individual metal nanostructures. PMID:19453164

  18. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    NASA Astrophysics Data System (ADS)

    Bahar, M. K.; Soylu, A.

    2015-05-01

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  19. Ultra-sensitive atomic magnetometer for studying magnetization fields produced by hyperpolarized helium-3

    NASA Astrophysics Data System (ADS)

    Zou, Sheng; Zhang, Hong; Chen, Xi-yuan; Chen, Yao; Lu, Ji-xi; Hu, Zhao-hui; Shan, Guang-cun; Quan, Wei; Fang, Jian-cheng

    2016-04-01

    An ingenious approach to acquire the absolute magnetization fields produced by polarized atoms has been presented in this paper. The method was based on detection of spin precession signal of the hyperpolarized helium-3 with ultra-sensitive atomic magnetometer of potassium by referring to time-domain analysis. At first, dynamic responses of the mixed spin ensembles in the presence of variant external magnetic fields have been analyzed by referring to the Bloch equation. Subsequently, the relevant equipment was established to achieve the functions of hyperpolarizing helium-3 and detecting the precession of spin-polarized noble gas. By analyzing the transient response of the magnetometer in time domain, we obtained the relevant damping ratio and natural frequency. When the value of damping ratio reached the maximum value of 0.0917, the combined atomic magnetometer was in equilibrium. We draw a conclusion from the steady response: the magnetization fields of the polarized electrons and the hyperpolarized nuclei were corresponding 16.12 nT and 90.74 nT. Under this situation, the nuclear magnetization field could offset disturbing magnetic fields perpendicular to the orientation of the electronic polarization, and it preserved the electronic spin staying in a stable axis. Therefore, the combined magnetometer was particularly attractive for inertial measurements.

  20. Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

    SciTech Connect

    Bahar, M. K.; Soylu, A.

    2015-05-15

    In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

  1. Average atom transport properties for pure and mixed species in the hot and warm dense matter regimes

    SciTech Connect

    Starrett, C. E.; Kress, J. D.; Collins, L. A.; Hanson, D. E.; Clerouin, J.; Recoules, V.

    2012-10-15

    The Kubo-Greenwood formulation for calculation of optical conductivities with an average atom model is extended to calculate thermal conductivities. The method is applied to species and conditions of interest for inertial confinement fusion. For the mixed species studied, the partial pressure mixing rule is used. Results including pressures, dc, and thermal conductivities are compared to ab initio calculations. Agreement for pressures is good, for both the pure and mixed species. For conductivities, it is found that the ad hoc renormalization method with line broadening, described in the text, gives best agreement with the ab initio results. However, some disagreement is found and the possible reasons for this are discussed.

  2. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    DOE PAGESBeta

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  3. Atomic electric dipole moment induced by the nuclear electric dipole moment: The magnetic moment effect

    SciTech Connect

    Porsev, S. G.; Ginges, J. S. M.; Flambaum, V. V.

    2011-04-15

    We have considered a mechanism for inducing a time-reversal violating electric dipole moment (EDM) in atoms through the interaction of a nuclear EDM d{sub N} with the hyperfine interaction, the ''magnetic moment effect''. We have derived the operator for this interaction and presented analytical formulas for the matrix elements between atomic states. Induced EDMs in the diamagnetic atoms {sup 129}Xe, {sup 171}Yb, {sup 199}Hg, {sup 211}Rn, and {sup 225}Ra have been calculated numerically. From the experimental limits on the atomic EDMs of {sup 129}Xe and {sup 199}Hg we have placed the following constraints on the nuclear EDMs, |d{sub N}({sup 129}Xe)|<1.1x10{sup -21}|e|cm and |d{sub N}({sup 199}Hg)|<2.8x10{sup -24}|e|cm.

  4. Construction and applications of an atomic magnetic gradiometerbased on nonlinear magneto-optical rotation

    SciTech Connect

    Xu, Shoujun; Rochester, Simon M.; Yashchuk, Valeriy V.; Donaldson, Marcus H.; Budker, Dmitry

    2006-06-28

    We report on the design, characterization, and applicationsof a sensitive atomic magnetic gradiometer. The device is based onnonlinear magneto-optical rotation in alkali-metal (87Rb) vapor, and usesfrequency-modulated laser light. The magnetic field produced by a sampleis detected by measuring the frequency of a resonance in optical rotationthat arises when the modulation frequency equals twice the Larmorprecession frequency of the Rb atoms. The gradiometer consists of twoatomic magnetometers. The rotation of light polarization in eachmagnetometer is detected with a balanced polarimeter. The sensitivity ofthe gradiometer is 0.8 nG/Hz1/2 for near-DC (0.1 Hz) magnetic fields,with a baseline of 2.5 cm. For applications in nuclear magnetic resonance(NMR) and magnetic resonance imaging (MRI), a long solenoid that piercesthe magnetic shields provides a ~;0.5 G leading field for the nuclearspins in the sample. Our apparatus is particularly suited for remotedetection of NMR and MRI. We demonstrate a point-by-point free inductiondecay measurement and a spin echo reconstructed with a pulse sequencesimilar to the Carr-Purcell-Meiboom-Gill (CPMG) pulse. Additionalapplications and future improvements are also discussed.

  5. Energetics, diffusion, and magnetic properties of cobalt atom in a monolayer graphene: An ab initio study

    SciTech Connect

    Raji, Abdulrafiu T.; Lombardi, Enrico B.

    2015-09-21

    We use ab initio methods to study the binding, diffusion, and magnetic properties of cobalt atom embedded in graphene vacancies. We investigate the diffusion of Co-monovacancy (Co-MV) and Co-divacancy (Co-DV) defect complexes, and determine the minimum energy path (MEP), as well as the activation energy barrier of migration. We obtained similar activation energy barriers, of ∼5.8 eV, for Co-MV and Co-DV diffusion, respectively. Our calculations also suggest that, at electron–irradiation energy of 200 keV as used in a related experiment, the maximum energy transfer to the Co atom, of approximately 9.0 eV is sufficiently high to break metal-carbon bonding. The incident electron energy is also high enough to displace graphene's carbon atoms from their lattice positions. The breaking of metal-carbon bonding and the displacement of graphene atoms may act to facilitate the migration of Co. We conclude therefore that the detrapping and diffusion of cobalt as observed experimentally is likely to be radiation-induced, similar to what has been observed for Au and Fe in electron-irradiated graphene. Furthermore, we show that Co migration in graphene is such that its magnetic moment varies along the diffusion path. The magnetic moment of Co is consistently higher in Co-DV diffusion when compared to that of Co-MV diffusion.

  6. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications.

  7. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition.

    PubMed

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications. PMID:26813143

  8. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition

    DOE PAGESBeta

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-27

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe2O3with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulatormore » transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. Finally, the ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications.« less

  9. Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition

    PubMed Central

    Zhang, Yijun; Liu, Ming; Peng, Bin; Zhou, Ziyao; Chen, Xing; Yang, Shu-Ming; Jiang, Zhuang-De; Zhang, Jie; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 with a blocking temperature of 120 K are in-situ obtained by finely controlling the oxidation reaction. Both of them exhibit a very small grain size of only several nanometers due to the nature of atom-by-atom growth of the ALD technique. Post-annealing α-Fe2O3 in a reducing atmosphere leads to the formation of the spinel Fe3O4 phase which displays a distinct ferrimagnetic anisotropy and the Verwey metal-insulator transition that usually takes place only in single crystal magnetite or thick epitaxial films at low temperatures. The ALD deposition of iron oxide with well-controlled phase and tunable magnetism demonstrated in this work provides a promising opportunity for the fabrication of 3D nano-devices to be used in catalysis, spintronics, microelectronics, data storages and bio-applications. PMID:26813143

  10. Controlling the magnetic-field sensitivity of atomic-clock states by microwave dressing

    NASA Astrophysics Data System (ADS)

    Sárkány, L.; Weiss, P.; Hattermann, H.; Fortágh, J.

    2014-11-01

    We demonstrate control of the differential Zeeman shift between clock states of ultracold rubidium atoms by means of nonresonant microwave dressing. Using the dc field dependence of the microwave detuning, we suppress the first- and second-order differential Zeeman shift in magnetically trapped 87Rb atoms. By dressing the state pair 5 S1 /2 F =1 , mF=-1 and F =2 , mF=1 , a residual frequency spread of <0.1 Hz in a range of 100 mG around a chosen magnetic offset field can be achieved. This is one order of magnitude smaller than the shift of the bare states at the magic field of the Breit-Rabi parabola. We further identify double magic points, around which the clock frequency is insensitive to fluctuations both in the magnetic field and in the dressing Rabi frequency. The technique is compatible with chip-based cold-atom systems and allows the creation of clock and qubit states with reduced sensitivity to magnetic-field noise.

  11. Temperature and phase-space density of a cold atom cloud in a quadrupole magnetic trap

    NASA Astrophysics Data System (ADS)

    Ram, S. P.; Mishra, S. R.; Tiwari, S. K.; Rawat, H. S.

    2014-08-01

    We present studies on modifications in the temperature, number density and phase-space density when a laser-cooled atom cloud from optical molasses is trapped in a quadrupole magnetic trap. Theoretically, for a given temperature and size of the cloud from the molasses, the phase-space density in the magnetic trap is shown first to increase with increasing magnetic field gradient and then to decrease with it after attaining a maximum value at an optimum value of the magnetic-field gradient. The experimentally-measured variation in the phase-space density in the magnetic trap with changing magnetic field gradient is shown to exhibit a similar trend. However, the experimentally-measured values of the number density and the phase-space density are much lower than the theoretically-predicted values. This is attributed to the experimentally-observed temperature in the magnetic trap being higher than the theoretically-predicted temperature. Nevertheless, these studies can be useful for setting a higher phase-space density in the trap by establishing an optimal value of the field gradient for a quadrupole magnetic trap.

  12. Magnetic Relaxometry with an Atomic Magnetometer and SQUID Sensors on Targeted Cancer Cells

    PubMed Central

    Johnson, Cort; Adolphi, Natalie L.; Butler, Kimberly L.; Debbie M, Lovato; Larson, Richard; Schwindt, Peter D.D.; Flynn, Edward R.

    2012-01-01

    Magnetic relaxometry methods have been shown to be very sensitive in detecting cancer cells and other targeted diseases. Superconducting Quantum Interference Device (SQUID) sensors are one of the primary sensor systems used in this methodology because of their high sensitivity with demonstrated capabilities of detecting fewer than 100,000 magnetically-labeled cancer cells. The emerging technology of atomic magnetometers (AM) represents a new detection method for magnetic relaxometry with high sensitivity and without the requirement for cryogens. We report here on a study of magnetic relaxometry using both AM and SQUID sensors to detect cancer cells that are coated with superparamagnetic nanoparticles through antibody targeting. The AM studies conform closely to SQUID sensor results in the measurement of the magnetic decay characteristics following a magnetization pulse. The AM and SQUID sensor data are well described theoretically for superparamagnetic particles bound to cells and the results can be used to determine the number of cells in a cell culture or tumor. The observed fields and magnetic moments of cancer cells are linear with the number of cells over a very large range. The AM sensor demonstrates very high sensitivity for detecting magnetically labeled cells does not require cryogenic cooling and is relatively inexpensive. PMID:22773885

  13. Magnetic Properties of Polycrystalline Bismuth Ferrite Thin Films Grown by Atomic Layer Deposition.

    PubMed

    Jalkanen, Pasi; Tuboltsev, Vladimir; Marchand, Benoît; Savin, Alexander; Puttaswamy, Manjunath; Vehkamäki, Marko; Mizohata, Kenichiro; Kemell, Marianna; Hatanpää, Timo; Rogozin, Valentin; Räisänen, Jyrki; Ritala, Mikko; Leskelä, Markku

    2014-12-18

    The atomic layer deposition (ALD) method was applied to grow thin polycrystalline BiFeO3 (BFO) films on Pt/SiO2/Si substrates. The 50 nm thick films were found to exhibit high resistivity, good morphological integrity, and homogeneity achieved by the applied ALD technique. Magnetic characterization revealed saturated magnetization of 25 emu/cm(3) with temperature-dependent coercivity varying from 5 to 530 Oe within the temperature range from 300 to 2 K. Magnetism observed in the films was found to change gradually from ferromagnetic spin ordering to pinned magnetic domain interactions mixed with weak spin-glass-like behavior of magnetically frustrated antiferromagnetic/ferromagnetic (AFM-FM) spin ordering depending on the temperature and magnitude of the applied magnetic field. Antiferromagnetic order of spin cycloids was broken in polycrystalline films by crystal sizes smaller than the cycloid length (∼60 nm). Uncompensated spincycloids and magnetic domain walls were found to be the cause of the high magnetization of the BFO films. PMID:26273981

  14. The magnetism and spin-dependent electronic transport properties of boron nitride atomic chains.

    PubMed

    An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Jiao, Zhaoyong; Wang, Kun

    2016-07-28

    Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 μB for BnNn-1, 2 μB for BnNn, and 3 μB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied. PMID:27475355

  15. Inducing Resonant Interactions in Ultracold Atoms with a Modulated Magnetic Field

    NASA Astrophysics Data System (ADS)

    Smith, D. Hudson

    2015-11-01

    In systems of ultracold atoms, pairwise interactions can be resonantly enhanced by a new mechanism that does not rely upon a magnetic Feshbach resonance. In this mechanism, interactions are controlled by tuning the frequency of an oscillating parallel component of the magnetic field close to the transition frequency between the scattering atoms and a two-atom bound state. The real part of the resulting s -wave scattering length a is resonantly enhanced when the oscillation frequency is close to the transition frequency. The resonance parameters can be controlled by varying the amplitude of the oscillating field. The amplitude also controls the imaginary part of a , which arises because the oscillating field converts atom pairs into molecules. The real part of a can be made much larger than the background scattering length without introducing catastrophic atom losses from the imaginary part. For the case of a shallow bound state in the scattering channel, the dimensionless resonance parameters are universal functions of the dimensionless oscillation amplitude.

  16. Richard L. Greene Dissertation Award in Experimental Condensed Matter or Materials Physics Talk: Towards single atom magnets

    NASA Astrophysics Data System (ADS)

    Baumann, Susanne

    Magnetic anisotropy is a fundamental property of magnetic materials that governs the stability and directionality of their magnetization. At the atomic level, magnetic anisotropy originates from anisotropy in the orbital angular momentum (L) and the spin-orbit coupling that connects the spin moment of a magnetic atom to the spatial symmetry of its ligand field environment. Generally, the ligand field, that is necessary for the anisotropy, also quenches the orbital moment and reduces the total magnetic moment of the atom to its spin component. However, careful design of the coordination geometry of a single atom can restore the orbital moment while inducing uniaxial anisotropy, as we present here for single atoms deposited on top of a thin MgO film. Scanning tunneling spectroscopy and x-ray absorption spectroscopy measurements show a large magnetic anisotropy of 19 meV for iron and 58 meV for cobalt, as well as relaxation times of many milliseconds. These results offer a strategy, based on symmetry arguments and careful tailoring of the interaction with the environment, for the rational design of nanoscopic permanent magnets and single atom magnets.

  17. Uniform synthetic magnetic field and effective mass for cold atoms in a shaken optical lattice.

    NASA Astrophysics Data System (ADS)

    Sols, Fernando; Creffield, Charles E.; Pieplow, Gregor; Goldman, Nathan

    2016-05-01

    Cold atoms can be made to experience synthetic magnetic fields when placed in a suitably driven optical lattice. For coherent systems the switching protocol plays an essential role in determining the long time behavior. Relatively simple driving schemes may generate a uniform magnetic flux but an inhomogeneous effective mass. A two-stage split driving scheme can recover a uniform effective mass but at the price of rendering the magnetic field space dependent. We propose a four-stage split driving that generates uniform field and mass of arbitrary values for all driving amplitudes. Finally, we study a modified two-stage split driving approach that enables uniform field and mass for most of but not all values of the magnetic field. Work supported by MINECO (Spain) under Grant FIS2013-41716-P, by FRS-FNRS (Belgium), and by BSPO under PAI Project No. P7/18 DYGEST.

  18. New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques

    DOE PAGESBeta

    Tang, W.; Zhou, L.; Kassen, A. G.; Palasyuk, A.; White, E. M.; Dennis, K. W.; Kramer, M. J.; McCallum, R. W.; Anderson, I. E.

    2015-05-25

    Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (Hcj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology. Asmore » a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.« less

  19. New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques

    SciTech Connect

    Tang, W.; Zhou, L.; Kassen, A. G.; Palasyuk, A.; White, E. M.; Dennis, K. W.; Kramer, M. J.; McCallum, R. W.; Anderson, I. E.

    2015-05-25

    Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (Hcj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology. As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.

  20. Conductance of ferro- and antiferro-magnetic single-atom contacts: A first-principles study

    SciTech Connect

    Tan, Zhi-Yun; Zheng, Xiao-long; Ye, Xiang; Xie, Yi-qun; Ke, San-Huang

    2013-08-14

    We present a first-principles study on the spin dependent conductance of five single-atom magnetic junctions consisting of a magnetic tip and an adatom adsorbed on a magnetic surface, i.e., the Co-Co/Co(001) and Ni-X/Ni(001) (X = Fe, Co, Ni, Cu) junctions. When their spin configuration changes from ferromagnetism to anti-ferromagnetism, the spin-up conductance increases while the spin-down one decreases. For the junctions with a magnetic adatom, there is nearly no spin valve effect as the decreased spin-down conductance counteracts the increased spin-up one. For the junction with a nonmagnetic adatom (Ni-Cu/Ni(001)), a spin valve effect is obtained with a variation of 22% in the total conductance. In addition, the change in spin configuration enhances the spin filter effect for the Ni-Fe/Ni(001) junction but suppresses it for the other junctions.

  1. Magnetic-resonance imaging of the human brain with an atomic magnetometer

    PubMed Central

    Savukov, I.; Karaulanov, T.

    2013-01-01

    Magnetic resonance imaging (MRI) is conventionally performed in very high fields, and this leads to some restrictions in applications. To remove such restrictions, the ultra-low field MRI approach has been proposed. Because of the loss of sensitivity, the detection methods based on superconducting quantum interference devices (SQUIDs) in a shielded room were used. Atomic magnetometers have similar sensitivity as SQUIDs and can also be used for MRI, but there are some technical difficulties to overcome. We demonstrate that MRI of the human brain can be obtained with an atomic magnetometer with in-plane resolution of 3 mm in 13 min. PMID:23964134

  2. Magnetically driven anisotropic structural changes in the atomic laminate M n2GaC

    NASA Astrophysics Data System (ADS)

    Dahlqvist, M.; Ingason, A. S.; Alling, B.; Magnus, F.; Thore, A.; Petruhins, A.; Mockute, A.; Arnalds, U. B.; Sahlberg, M.; Hjörvarsson, B.; Abrikosov, I. A.; Rosen, J.

    2016-01-01

    Inherently layered magnetic materials, such as magnetic Mn +1A Xn (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition Mn+1A Xn consists of Mn +1Xn blocks separated by atomically thin A -layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic M n2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of M n2GaC MAX phases in future magnetoelectric and magnetocaloric applications.

  3. Static electric and magnetic multipole susceptibilities for Dirac one-electron atoms in the ground state

    NASA Astrophysics Data System (ADS)

    Szmytkowski, Radosław; Łukasik, Grzegorz

    2016-09-01

    We present tabulated data for several families of static electric and magnetic multipole susceptibilities for hydrogenic atoms with nuclear charge numbers from the range 1 ⩽ Z ⩽ 137. Atomic nuclei are assumed to be point-like and spinless. The susceptibilities considered include the multipole electric polarizabilities α E L → E L and magnetizabilities (magnetic susceptibilities) χ M L → M L with 1 ⩽ L ⩽ 4 (i.e., the dipole, quadrupole, octupole and hexadecapole ones), the electric-to-magnetic cross-susceptibilities α E L → M(L - 1) with 2 ⩽ L ⩽ 5 and α E L → M(L + 1) with 1 ⩽ L ⩽ 4, the magnetic-to-electric cross-susceptibilities χ M L → E(L - 1) with 2 ⩽ L ⩽ 5 and χ M L → E(L + 1) with 1 ⩽ L ⩽ 4 (it holds that χ M L → E(L ∓ 1) =α E(L ∓ 1) → M L), and the electric-to-toroidal-magnetic cross-susceptibilities α E L → T L with 1 ⩽ L ⩽ 4. Numerical values are computed from general exact analytical formulas, derived by us elsewhere within the framework of the Dirac relativistic quantum mechanics, and involving generalized hypergeometric functions 3F2 of the unit argument.

  4. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    PubMed

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications. PMID:23171130

  5. Quantum beats in the field ionization of Rydberg atoms in the presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Gregoric, Vincent C.; Hastings, Hannah; Carroll, Thomas J.; Noel, Michael W.

    2016-05-01

    By exciting a coherent superposition and varying its phase evolution, quantum beats in the selective field ionization of Rydberg atoms have been observed. Here, we present a study exploring the effect of electric and magnetic fields on quantum beats. Beginning with a single excited state, a coherent superposition is created by a short electric field pulse in the presence of a static magnetic field. The resulting quantum beats are then observed in the field ionization spectrum. Additionally, millimeter-wave spectroscopy is used to probe the state populations in this superposition. This work is supported by the National Science Foundation under Grants No. 1205895 and No. 1205897.

  6. Experimentally attainable example of chaotic tunneling: The hydrogen atom in parallel static electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Delande, Dominique; Zakrzewski, Jakub

    2003-12-01

    Statistics of tunneling rates in the presence of chaotic classical dynamics is discussed on a realistic example: a hydrogen atom placed in parallel, uniform, static electric, and magnetic fields, where tunneling is followed by ionization along the fields direction. Depending on the magnetic quantum number, one may observe either a standard Porter-Thomas distribution of tunneling rates or, for strong scarring by a periodic orbit parallel to the external fields, strong deviations from it. For the latter case, a simple model based on random matrix theory gives the correct distribution.

  7. Structural and Magnetic Evolution of Bimetallic MnAu Clusters Driven by Asymmetric Atomic Migration

    SciTech Connect

    Wei, Xiaohui; Zhou, Rulong; Lefebvre, Williams; He, Kai; Le Roy, Damien; Skomski, Ralph; Li, Xingzhong; Shield, Jeffrey E; Kramer, Matthew J; Chen, Shuang; Zeng, Xiao Cheng; Sellmyer, David J

    2014-03-12

    The nanoscale structural, compositional, and magnetic properties are examined for annealed MnAu nanoclusters. The MnAu clusters order into the L10 structure, and monotonic size-dependences develop for the composition and lattice parameters, which are well reproduced by our density functional theory calculations. Simultaneously, Mn diffusion forms 5 Å nanoshells on larger clusters inducing significant magnetization in an otherwise antiferromagnetic system. The differing atomic mobilities yield new cluster nanostructures that can be employed generally to create novel physical properties.

  8. Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

    DOE PAGESBeta

    Rusz, Jan; Idrobo, Juan -Carlos; Bhowmick, Somnath

    2014-09-30

    The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strongmore » as those obtained by nanodiffraction methods.« less

  9. Hydrogen atom in a magnetic field: Ghost orbits, catastrophes, and uniform semiclassical approximations

    SciTech Connect

    Main, J.; Wunner, G.

    1997-03-01

    Applying closed-orbit theory to the recurrence spectra of the hydrogen atom in a magnetic field, one can interpret most, but not all, structures semiclassically in terms of closed classical orbits. In particular, conventional closed-orbit theory fails near bifurcations of orbits where semiclassical amplitudes exhibit unphysical divergences. Here we analyze the role of ghost orbits living in complex phase space. The ghosts can explain resonance structures in the spectra of the hydrogen atom in a magnetic field at positions where no real orbits exist. For three different types of catastrophes, viz. fold, cusp, and butterfly catastrophes, we construct uniform semiclassical approximations and demonstrate that these solutions are completely determined by classical parameters of the real orbits and complex ghosts. {copyright} {ital 1997} {ital The American Physical Society}

  10. Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

    SciTech Connect

    Rusz, Jan; Idrobo, Juan -Carlos; Bhowmick, Somnath

    2014-09-30

    The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strong as those obtained by nanodiffraction methods.

  11. Born–Oppenheimer Approximation for an Atom in Constant Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ashida, Sohei

    2016-08-01

    We obtain a reduction scheme for the study of the quantum evolution of an atom in constant magnetic fields using the method developed by Martinez, Nenciu and Sordoni based on the construction of almost invariant subspace. In Martinez-Sordoni \\cite{MaSo2} such a case is also studied but their reduced Hamiltonian includes the vector potential terms. In this paper, using the center of mass coordinates and constructing the almost invariant subspace different from theirs, we obtain the reduced Hamiltonian which does not include the vector potential terms. Using the reduced evolution we also obtain the asymptotic expantion of the evolution for a specific localized initial data, which verifies the straight motion of an atom in constatnt magnetic fields.

  12. Ionization of an Highly Excited Hydrogen atom in parallel Electric and Magnetic fields

    NASA Astrophysics Data System (ADS)

    Topçu, T.&Ürker; Robicheaux, Francis

    2006-05-01

    In a recent paper, Mitchell et al [Phys. Rev. Lett. 92, 073001 (2004)] investigated the ionization of a classical hydrogen atom in parallel electric and magnetic fields. They reported epistrophic self- similar pulse trains of ionized electrons attributed to the classical chaos induced by the magnetic field. We study hydrogen atom in an excited state with n˜80 in parallel external fields as an example of an open, chaotic quantum system in the time domain. We investigate the effect of interference between the outgoing pulse trains which is absent in the classical picture. We look at interference effect as a function of the energy since Schr"odinger equation does not scale as the classical equations of motion do. We compare and contrast our quantum results with the classical results of Mitchell et al.

  13. Assessment of ion-atom collision data for magnetic fusion plasma edge modelling

    NASA Astrophysics Data System (ADS)

    Phaneuf, R. A.

    Cross-section data for ion-atom collision processes which play important roles in the edge plasma of magnetically-confined fusion devices are surveyed and reviewed. The species considered include H, He, Li, Be, C, O, Ne, Al, Si, Ar, Ti, Cr, Fe, Ni, Cu, Mo, W and their ions. The most important ion-atom collision processes occurring in the edge plasma are charge-exchange reactions. Excitation and ionization processes are also considered. The scope is limited to atomic species and to collision velocities corresponding to plasma ion temperatures in the 2 to 200 eV range. Sources of evaluated or recommended data are presented where possible, and deficiencies in the data base are indicated.

  14. The migration behavior of atomic clusters in early nanocrystalline process of soft magnetic Finemet alloy.

    PubMed

    Wang, Yuxin; Li, Xiang; Zhang, Yu; Zhao, Guannan; Yan, Biao; Lu, Wei

    2010-11-01

    The Finemet alloys are commonly used as cores in transformers and generators, stress and field sensors in technological application for their excellent soft magnetic characteristics. To clarify the nanocrystallization mechanism of Finemet especially about the atomic migration in early stage is very essential for developing their distinctive characteristics. In this study, we investigate the migration behavior of atoms in order to clarify the mechanism of the early-stage nanocrystallization in amorphous Finemet alloys. The Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous ribbons were prepared by single-roller melt-spinning process in argon atmosphere, and then annealed at 350 degrees C-400 degrees C for 10 minutes in vacuum. The atom force microscope (AFM) and the coincidence Doppler broadening spectra (CDB) were used to characterize the migration behavior of different atoms in Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous alloy during the early-stage nanocrystallization. The X-ray diffraction (XRD) patterns show that all annealed samples are in the amorphous state. But the AFM observation shows clearly that there are many small atomic clusters (nuclei) which distribute in the amorphous matrix of the annealed samples. With increasing annealing temperature, there is a significant increase in the amount of atomic clusters and a dramatic drop in the average size of clusters with very limited Cu contention in the samples, which reflect the structural evolution into more homogeneity. The CDB spectrum indicates that the peaks of positron annihilation spectrum are gradually reduced, which means the number of grain boundary and the defects in samples are gradually increased. It can be concluded that more defects are introduced by the formation of atomic clusters through atomic migration during the early-stage nanocrystallization in Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous alloys. PMID:21137965

  15. Magnetic induction imaging with optical atomic magnetometers: towards applications to screening and surveillance

    NASA Astrophysics Data System (ADS)

    Marmugi, Luca; Hussain, Sarah; Deans, Cameron; Renzoni, Ferruccio

    2015-10-01

    We propose a new approach, based on optical atomic magnetometers and magnetic induction tomography (MIT), for remote and non-invasive detection of conductive targets. Atomic magnetometers overcome the main limitations of conventional MIT instrumentation, in particular their poor low-frequency sensitivity, their large size and their limited scalability. Moreover, atomic magnetometers have been proven to reach extremely high sensitivities, with an improvement of up to 7 orders of magnitude in the 50 MHz to DC band, with respect to a standard pick-up coil of the same size. In the present scheme, an oscillating magnetic field induces eddy currents in a conductive target and laser-pumped atomic magnetometers, either stand-alone or in an array, detect the response of the objects. A phase-sensitive detection scheme rejects the background, allowing remote detection of the secondary field and, thus, mapping of objects, hidden in cargos, underwater or underground. The potential for extreme sensitivity, miniaturization, dynamic range and array operation paves the way to a new generation of non-invasive, active detectors for surveillance, as well as for real-time cargo screening.

  16. Atomic scale study of magnetic phase transitions in (Co,Ti;Sc) substituted nanosize barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Krezhov, Kiril

    BaFe12O19 and related isostructural (M-type) hexaferrites derived by single or double cation substitution for Fe3+ with preservation of the formal valence are a recognized group of oxides for their remarkable properties. The magnetic interactions may be tuned by suitable substitutions resulting in notable magnetic properties utilized extensively for permanent magnets, microwave devices and perpendicular recording media. We report on the magnetic structure evolution accompanying the magnetic anisotropy change, from a combined magnetic (SQUID), x-ray and neutron diffraction, and magnetic field dependent 57Fe Mössbauer study on BaFe12O19 at selected cation substitutions. The short and long range atomic and magnetic order in powder samples of nanosize particles prepared by soft chemistry routes were studied and compared with own and literature data for the parent BaFe12O19 compound prepared by solid state reaction. Refinements based on diffraction data show that the magnetic structures of BaFe12-xXxO19 (X=Co,Ti; Sc) hexaferrites are largely temperature and substitution dependent. Between 200 and 300K the (Co,Ti)-hexaferrites (x=0.4, 0.7, 0.8, 0.85) display ferrimagnetic structures where the canting of the magnetic moments depends on the substitution rate. When lowering the temperature the magnetic structure for x=0.45 remains ferrimagnetic down to 10 K, while for x=0.7 and x=0.8 a complex conical magnetic structures is finally established. For x=0.85 significant distortions in the local oxygen surrounding of ferric cation sites were established, while the grain-size effect on the structural parameters was considerably smaller. The thermal expansion coefficient exhibits a strong anisotropy. The refined magnetic moments are considerably lower than the theoretical spin only moments, especially for the 4e and 12k sites, indicating a local noncollinearity with short-range ordering. The five-cation sublattice collinear ferrimagnetic structure of uniaxial type known as

  17. High-frequency magnetization dynamics of individual atomic-scale magnets

    NASA Astrophysics Data System (ADS)

    Krause, S.; Sonntag, A.; Hermenau, J.; Friedlein, J.; Wiesendanger, R.

    2016-02-01

    The magnetization dynamics of individual nanomagnets is studied by spin-polarized scanning tunneling microscopy, combining real-time telegraphic noise analysis with pump-probe schemes. A transition between two Arrhenius regimes is observed as a function of temperature. The switching rates at high temperature are found to be orders of magnitude lower than expected from the extrapolation from the low-temperature regime. A four-state hopping model of magnetization reversal is developed to interpret the experimental results in terms of nucleation, annihilation, and propagation.

  18. Magnetic-field-induced quadrupole coupling in the nuclear magnetic resonance of noble-gas atoms and molecules

    SciTech Connect

    Manninen, Pekka; Vaara, Juha; Pyykkoe, Pekka

    2004-10-01

    An analytic response theory formulation for the leading-order magnetic field-induced and field-dependent quadrupole splitting in nuclear magnetic resonance spectra is presented and demonstrated with first-principles calculations for {sup 21}Ne, {sup 36}Ar, and {sup 83}Kr in noble gas atoms. The case of molecules was studied for {sup 33}S in the sulphur hexafluoride molecule, as well as for {sup 47/49}Ti, {sup 91}Zr, and {sup 177,179}Hf in group(IV) tetrahalides. According to our calculations, the hitherto experimentally unknown field-induced quadrupole splitting in molecules rises to 10{sup 2} Hz for {sup 177,179}Hf nuclei in HfF{sub 4} and 10{sup 1} Hz for {sup 47/49}Ti in TiCl{sub 4}, and is hence of observable magnitude.

  19. Time-dependent atomic diffusion in magnetic ApBp stars

    NASA Astrophysics Data System (ADS)

    Stift, M. J.; Alecian, G.

    2016-03-01

    Numerical modelling of surface abundance distributions in ApBp star atmospheres constitutes a challenging astrophysical problem. This paper is intended to deepen our understanding of how atomic diffusion affects the atmospheric structure of magnetic ApBp stars, and in particular how time-dependent calculations may be compared to the alternative method of estimating equilibrium stratifications. Our numerical calculations - with the stellar atmosphere adjusted self-consistently to the abundance profiles - show that final stationary solutions of the time-dependent diffusion problem (constant particle flux throughout the stellar atmosphere) are seemingly at variance with equilibrium stratifications (zero particle flux). In this work, we will provide some understanding of the origin of these differences and try to elucidate the as yet little explored behaviour of time-dependent atomic diffusion. To this purpose, we assess the influence of the boundary condition at the bottom of the atmosphere, we investigate how the stratifications depend on magnetic field angle and strength, and we have a look at possible interactions between different chemical elements. Based on a grid of atmospheric models and stratifications reflecting dipolar magnetic geometries, we also present predicted line profiles for different oblique rotator models. Finally, we shortly discuss the consequences of our findings for the interpretation of abundance maps of magnetic ApBp stars.

  20. THE IMPRINT OF THE VERY LOCAL INTERSTELLAR MAGNETIC FIELD IN SIMULATED ENERGETIC NEUTRAL ATOM MAPS

    SciTech Connect

    Prested, C.; Schwadron, N.; Opher, M. E-mail: nathanas@bu.ed

    2010-06-10

    The interaction of the solar wind with the very local interstellar medium (VLISM) forms the boundaries of the heliosphere. A strong asymmetry of the heliosphere was found both directly by the Voyager probes and indirectly from measurements of the deflection of neutral hydrogen. The most likely source of this asymmetry is from the interstellar magnetic field, the properties of which are highly unconstrained. Energetic neutral atom (ENA) images will provide an additional method to view the heliosphere and infer the interstellar magnetic field. This paper investigates the imprint of the interstellar magnetic field on simulated energetic neutral atom all-sky maps. We show that a significant source of 0.5-1 keV ENAs may originate from the outside of the heliopause, if a strong suprathermal population exists in the VLISM. In simulations, a strong outer heliosheath ENA feature appears near the nose of the heliosphere. A weaker, complementary feature is also present consisting entirely of inner heliosheath ENAs. From this feature the direction of the interstellar magnetic field can be easily inferred.

  1. Spin filtering and switching action in a diamond network with magnetic-nonmagnetic atomic distribution.

    PubMed

    Pal, Biplab; Dutta, Paramita

    2016-01-01

    We propose a simple model quantum network consisting of diamond-shaped plaquettes with deterministic distribution of magnetic and non-magnetic atoms in presence of a uniform external magnetic flux in each plaquette and predict that such a simple model can be a prospective candidate for spin filter as well as flux driven spintronic switch. The orientations and the amplitudes of the substrate magnetic moments play a crucial role in the energy band engineering of the two spin channels which essentially gives us a control over the spin transmission leading to a spin filtering effect. The externally tunable magnetic flux plays an important role in inducing a switch on-switch off effect for both the spin states indicating the behavior like a spintronic switch. Even a correlated disorder configuration in the on-site potentials and in the magnetic moments may lead to disorder-induced spin filtering phenomenon where one of the spin channel gets entirely blocked leaving the other one transmitting over the entire allowed energy regime. All these features are established by evaluating the density of states and the two terminal transmission probabilities using the transfer-matrix formalism within a tight-binding framework. Experimental realization of our theoretical study may be helpful in designing new spintronic devices. PMID:27600958

  2. Spin filtering and switching action in a diamond network with magnetic-nonmagnetic atomic distribution

    PubMed Central

    Pal, Biplab; Dutta, Paramita

    2016-01-01

    We propose a simple model quantum network consisting of diamond-shaped plaquettes with deterministic distribution of magnetic and non-magnetic atoms in presence of a uniform external magnetic flux in each plaquette and predict that such a simple model can be a prospective candidate for spin filter as well as flux driven spintronic switch. The orientations and the amplitudes of the substrate magnetic moments play a crucial role in the energy band engineering of the two spin channels which essentially gives us a control over the spin transmission leading to a spin filtering effect. The externally tunable magnetic flux plays an important role in inducing a switch on-switch off effect for both the spin states indicating the behavior like a spintronic switch. Even a correlated disorder configuration in the on-site potentials and in the magnetic moments may lead to disorder-induced spin filtering phenomenon where one of the spin channel gets entirely blocked leaving the other one transmitting over the entire allowed energy regime. All these features are established by evaluating the density of states and the two terminal transmission probabilities using the transfer-matrix formalism within a tight-binding framework. Experimental realization of our theoretical study may be helpful in designing new spintronic devices. PMID:27600958

  3. Tunable atomic spin-orbit coupling synthesized with a modulating gradient magnetic field

    PubMed Central

    Luo, Xinyu; Wu, Lingna; Chen, Jiyao; Guan, Qing; Gao, Kuiyi; Xu, Zhi-Fang; You, L.; Wang, Ruquan

    2016-01-01

    We report the observation of synthesized spin-orbit coupling (SOC) for ultracold spin-1 87Rb atoms. Different from earlier experiments where a one dimensional (1D) atomic SOC of pseudo-spin-1/2 is synthesized with Raman laser fields, the scheme we demonstrate employs a gradient magnetic field (GMF) and ground-state atoms, thus is immune to atomic spontaneous emission. The strength of SOC we realize can be tuned by changing the modulation amplitude of the GMF, and the effect of the SOC is confirmed through the studies of: 1) the collective dipole oscillation of an atomic condensate in a harmonic trap after the synthesized SOC is abruptly turned on; and 2) the minimum energy state at a finite adiabatically adjusted momentum when SOC strength is slowly ramped up. The condensate coherence is found to remain very good after driven by modulating GMFs. Our scheme presents an alternative means for studying interacting many-body systems with synthesized SOC. PMID:26752786

  4. Tunable atomic spin-orbit coupling synthesized with a modulating gradient magnetic field

    NASA Astrophysics Data System (ADS)

    Luo, Xinyu; Wu, Lingna; Chen, Jiyao; Guan, Qing; Gao, Kuiyi; Xu, Zhi-Fang; You, L.; Wang, Ruquan

    2016-01-01

    We report the observation of synthesized spin-orbit coupling (SOC) for ultracold spin-1 87Rb atoms. Different from earlier experiments where a one dimensional (1D) atomic SOC of pseudo-spin-1/2 is synthesized with Raman laser fields, the scheme we demonstrate employs a gradient magnetic field (GMF) and ground-state atoms, thus is immune to atomic spontaneous emission. The strength of SOC we realize can be tuned by changing the modulation amplitude of the GMF, and the effect of the SOC is confirmed through the studies of: 1) the collective dipole oscillation of an atomic condensate in a harmonic trap after the synthesized SOC is abruptly turned on; and 2) the minimum energy state at a finite adiabatically adjusted momentum when SOC strength is slowly ramped up. The condensate coherence is found to remain very good after driven by modulating GMFs. Our scheme presents an alternative means for studying interacting many-body systems with synthesized SOC.

  5. Atomic Regime in Which the Magnetic Interaction Dominates the Coulomb Interaction for Highly Excited States of Hydrogen

    PubMed Central

    Mueller, Ronald O.; Hughes, Vernon W.

    1974-01-01

    The atomic regime in which the interaction of the electron with an external magnetic field dominates the Coulomb interaction with the nucleus, relevant to pulsars, can be realized at laboratory magnetic fields for discrete autoionized states of hydrogen, at energies above the ionization limit. Approximate wave functions, energy levels, and electric dipole transition probabilities are presented for hydrogen, and an atomic beam absorption spectroscopy experiment at 50 kG is proposed to study this new regime. PMID:16578723

  6. Visualization and quantification of magnetic nanoparticles into vesicular systems by combined atomic and magnetic force microscopy

    SciTech Connect

    Dong, C.; Corsetti, S.; Passeri, D.; Rossi, M.; Carafa, M.; Marianecci, C.; Pantanella, F.; Rinaldi, F.; Ingallina, C.; Sorbo, A.

    2015-06-23

    We report a phenomenological approach for the quantification of the diameter of magnetic nanoparticles (MNPs) incorporated in non-ionic surfactant vesicles (niosomes) using magnetic force microscopy (MFM). After a simple specimen preparation, i.e., by putting a drop of solution containing MNPs-loaded niosomes on flat substrates, topography and MFM phase images are collected. To attempt the quantification of the diameter of entrapped MNPs, the method is calibrated on the sole MNPs deposited on the same substrates by analyzing the MFM signal as a function of the MNP diameter (at fixed tip-sample distance) and of the tip-sample distance (for selected MNPs). After calibration, the effective diameter of the MNPs entrapped in some niosomes is quantitatively deduced from MFM images.

  7. Entangled states of trapped ions allow measuring the magnetic field gradient produced by a single atomic spin

    NASA Astrophysics Data System (ADS)

    Schmidt-Kaler, F.; Gerritsma, R.

    2012-09-01

    We propose detecting the magnetic field gradient produced by the magnetic dipole moment of a single atom by using ions in an entangled state trapped a few μm from the dipole. This requires measuring magnetic field gradients of order 10-13 tesla/μm. We discuss applications in determining magnetic moments of a wide variety of ion species, for investigating the magnetic substructure of ions with level structures that are not suitable for laser cooling and detection, and for studying exotic or rare ions, and molecular ions. The scheme may also be used for measuring spin imbalances of neutral atoms or atomic ensembles trapped by optical dipole forces. As the proposed method relies on techniques that are well established in ion trap quantum information processing, it is within reach of current technology.

  8. Optically-Detected Magnetic Resonance of Alkali Atoms Isolated on Helium Nano-Droplets

    NASA Astrophysics Data System (ADS)

    Koch, Markus; Callegari, Carlo; Ernst, Wolfgang E.

    2009-06-01

    Sharp, hyperfine-resolved, ESR spectra of alkali atoms isolated on helium nanodroplets are measured by optically-detected magnetic resonance (ODMR). A net spin polarization is created inside a magnetic field (B=0.2 to 4.2 T) by a pump laser beam. Microwave radiation in a resonant cavity at 9.4 GHz causes a spin transition which is detected by a probe laser beam. For ultimate precision the spectrum of free atoms is concurrently measured and serves as a reference. The shift of the ESR lines on the droplet with respect to free atoms directly reflects the distortion of the valence-electron wavefunction due to the He nanodroplet. While the electron g-factor remains unchanged within experimental uncertainties (<5 ppm), the increase of the hyperfine constant (typically +400 ppm) is consistent with an increase of the Fermi contact interaction. We are able to follow this change as a function of droplet size attesting the sensitivity of the method for the measurement of chemical shifts. The observation of Rabi oscillations indicates a long decoherence time and proves our ability to perform coherent manipulation of the spin.

  9. Developing Density of Laser-Cooled Neutral Atoms and Molecules in a Linear Magnetic Trap

    NASA Astrophysics Data System (ADS)

    Velasquez, Joe, III; Walstrom, Peter; di Rosa, Michael

    2013-05-01

    In this poster we show that neutral particle injection and accumulation using laser-induced spin flips may be used to form dense ensembles of ultracold magnetic particles, i.e., laser-cooled paramagnetic atoms and molecules. Particles are injected in a field-seeking state, are switched by optical pumping to a field-repelled state, and are stored in the minimum-B trap. The analogous process in high-energy charged-particle accumulator rings is charge-exchange injection using stripper foils. The trap is a linear array of sextupoles capped by solenoids. Particle-tracking calculations and design of our linear accumulator along with related experiments involving 7Li will be presented. We test these concepts first with atoms in preparation for later work with selected molecules. Finally, we present our preliminary results with CaH, our candidate molecule for laser cooling. This project is funded by the LDRD program of Los Alamos National Laboratory.

  10. Two-Photon Frequency Comb Excitation of Rubidium Atoms in External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Vujičić, N.; Ban, T.; Skenderović, H.; Vdović, S.; Pichler, G.

    2008-10-01

    In the present experiment the 5S-5D two-photon transitions in 85Rb and 87Rb atoms as a result of the interaction of the femtosecond frequency comb with atomic levels of both rubidium isotopes are investigated. The main problem in studying of two-photon transitions is in optimization of the excitation efficiency of the desired state. There are two general cases: those transition with an intermediate resonance those in which the pulse spectrum is far detuned from an intermediate resonance. In order to investigate the dependence of the two-photon fluorescence signal as a result of interaction of the frequency comb with perturbed energy-level pattern an external magnetic field was applied.

  11. Two magnetic states of iron atoms in Invar Fe-Ni alloys and positron annihilation

    NASA Astrophysics Data System (ADS)

    Sedov, V. L.; Tsigel'nik, O. A.

    1999-11-01

    The temperature dependence of angular correlation annihilation radiation (ACAR) in Invar Fe-Ni alloys is investigated. It is found that the ACAR distribution in the Curie temperature region TC depends on temperature. This effect is created only by those positrons that are trapped by vacancies. The effect is enhanced if the positrons trapped by vacancy-hydrogen complexes. The ACAR distribution is changed due to enhanced interaction of these positrons with 3d electrons. A simple interpretation of this phenomenon can be given on the basis of the model of two magnetic states of Fe atoms in Invar alloys. According to this model the enhancement of the electron-positron correlation interaction in the TC region occurs as a result of the convergence of the energy levels εHS and εLS corresponding to the high-spin (HS) and low-spin (LS) states of Fe atoms.

  12. Electric and magnetic response in dielectric dark states for low loss subwavelength optical meta atoms

    DOE PAGESBeta

    Jain, Aditya; Moitra, Parikshit; Koschny, Thomas; Valentine, Jason; Soukoulis, Costas M.

    2015-07-14

    Artificially created surfaces or metasurfaces, composed of appropriately shaped subwavelength structures, namely, meta-atoms, control light at subwavelength scales. Historically, metasurfaces have used radiating metallic resonators as subwavelength inclusions. However, while resonant optical metasurfaces made from metal have been sufficiently subwavelength in the propagation direction, they are too lossy for many applications. Metasurfaces made out of radiating dielectric resonators have been proposed to solve the loss problem, but are marginally subwavelength at optical frequencies. We designed subwavelength resonators made out of nonradiating dielectrics. The resonators are decorated with appropriately placed scatterers, resulting in a meta-atom with an engineered electromagnetic response. Amore » metasurface that yields an electric response is fabricated, experimentally characterized, and a method to obtain a magnetic response at optical frequencies is theoretically demonstrated. In conclusion, this design methodology paves the way for metasurfaces that are simultaneously subwavelength and low loss.« less

  13. Electric and magnetic response in dielectric dark states for low loss subwavelength optical meta atoms

    SciTech Connect

    Jain, Aditya; Moitra, Parikshit; Koschny, Thomas; Valentine, Jason; Soukoulis, Costas M.

    2015-07-14

    Artificially created surfaces or metasurfaces, composed of appropriately shaped subwavelength structures, namely, meta-atoms, control light at subwavelength scales. Historically, metasurfaces have used radiating metallic resonators as subwavelength inclusions. However, while resonant optical metasurfaces made from metal have been sufficiently subwavelength in the propagation direction, they are too lossy for many applications. Metasurfaces made out of radiating dielectric resonators have been proposed to solve the loss problem, but are marginally subwavelength at optical frequencies. We designed subwavelength resonators made out of nonradiating dielectrics. The resonators are decorated with appropriately placed scatterers, resulting in a meta-atom with an engineered electromagnetic response. A metasurface that yields an electric response is fabricated, experimentally characterized, and a method to obtain a magnetic response at optical frequencies is theoretically demonstrated. In conclusion, this design methodology paves the way for metasurfaces that are simultaneously subwavelength and low loss.

  14. Visualizing Majorana fermions in a chain of magnetic atoms on a superconductor

    NASA Astrophysics Data System (ADS)

    Yazdani, Ali

    2015-12-01

    A chain of magnetic atoms on the surface of a superconductor provides a versatile platform for realizing a one-dimensional topological superconductivity phase with edge-bounded Majorana fermions zero modes. This platform lends itself to spatial resolved measurements with scanning tunneling microscope (STM) that enables direct visualization of the presence of a localized Majorana zero mode. Experiments on self-assembled chains of Fe atoms on the surface of Pb show that such a system can be experimentally fabricated and studied using various high-resolution STM measurement techniques. Spatial and energy resolved STM experiments provide strong evidence for Majorana bound states that emerge due to the combination of Fe’s ferromagnetism and spin-orbit coupling of the superconducting Pb substrate. These studies provide a roadmap for optimizing topological superconductivity in this one-dimensional platform and its extension to realize chiral two-dimensional superconductors.

  15. Protein folding at atomic resolution: analysis of autonomously folding supersecondary structure motifs by nuclear magnetic resonance.

    PubMed

    Sborgi, Lorenzo; Verma, Abhinav; Sadqi, Mourad; de Alba, Eva; Muñoz, Victor

    2013-01-01

    The study of protein folding has been conventionally hampered by the assumption that all single-domain proteins fold by an all-or-none process (two-state folding) that makes it impossible to resolve folding mechanisms experimentally. Here we describe an experimental method for the thermodynamic analysis of protein folding at atomic resolution using nuclear magnetic resonance (NMR). The method is specifically developed for the study of small proteins that fold autonomously into basic supersecondary structure motifs, and that do so in the sub-millisecond timescale (folding archetypes). From the NMR experiments we obtain hundreds of atomic unfolding curves that are subsequently analyzed leading to the determination of the characteristic network of folding interactions. The application of this approach to a comprehensive catalog of elementary folding archetypes holds the promise of becoming the first experimental approach capable of unraveling the basic rules connecting protein structure and folding mechanism. PMID:22987355

  16. Experimental study of linear magnetic dichroism in photoionization satellite transitions of atomic rubidium

    SciTech Connect

    Jaenkaelae, K.; Alagia, M.; Feyer, V.; Richter, R.; Prince, K. C.

    2011-11-15

    Laser orientation in the initial state has been used to study the properties of satellite transitions in inner-shell photoionization of rubidium atoms. The linear magnetic dichroism in the angular distribution (LMDAD) has been utilized to probe the continuum waves of orbital angular momentum conserving monopole, and angular momentum changing conjugate satellites, accompanying the 4p ionization of atomic Rb. We show experimentally that LMDAD of both types of satellite transitions is nonzero and that LMDAD of monopole satellites, measured as a function of photon energy, mimics the LMDAD of direct photoionization, whereas the LMDAD of conjugate transitions deviates drastically from that trend. The results indicate that conjugate transitions cannot be described theoretically without explicit inclusion of electron-electron interaction. The present data can thus be used as a very precise test of current models for photoionization.

  17. Atomic force microscopy-coupled microcoils for cellular-scale nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Mousoulis, Charilaos; Maleki, Teimour; Ziaie, Babak; Neu, Corey P.

    2013-04-01

    We present the coupling of atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) technologies to enable topographical, mechanical, and chemical profiling of biological samples. Here, we fabricate and perform proof-of-concept testing of radiofrequency planar microcoils on commercial AFM cantilevers. The sensitive region of the coil was estimated to cover an approximate volume of 19.4 × 103 μm3 (19.4 pl). Functionality of the spectroscopic module of the prototype device is illustrated through the detection of 1Η resonance in deionized water. The acquired spectra depict combined NMR capability with AFM that may ultimately enable biophysical and biochemical studies at the single cell level.

  18. Magnetic property of transition metal-Si atomic line on silicon Σ3 grain boundary: A theoretical study

    NASA Astrophysics Data System (ADS)

    Li, Yong-Hua; Guo, Shu-Kuan; Ma, Zhong-Quan; Qu, Guo-Hui; Shi, Ting-Ting; Gong, Xin-Gao; Xia, Qin; Wei, Su-Huai

    2014-06-01

    Using first-principles calculations within density functional theory, we investigate the electronic and magnetic properties of different 3d transition metal-Si atomic lines on silicon Σ3 (112) grain boundary, which can be formed through grain boundary segregation. We find that (i) Fe atoms occupy the substitutional sites at the grain boundary and form an Fe-Si atomic line, but the interaction between the Fe atoms is antiferromagnetic. (ii) The ferromagnetic stability increases with the atomic number of the transition metals and Co-Si atomic line is more stable in the ferromagnetic phase and shows a semimetallic behavior. We suggest that this special TM-Si atomic line formed by thermodynamically favorable transition metal segregation on Si grain boundary could be used in design of spin-dependent quantum devices.

  19. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  20. Magnetic dipolar interaction in a Bose-Einstein condensate atomic interferometer.

    PubMed

    Fattori, M; Roati, G; Deissler, B; D'Errico, C; Zaccanti, M; Jona-Lasinio, M; Santos, L; Inguscio, M; Modugno, G

    2008-11-01

    We study the role played by the magnetic dipole interaction in the decoherence of a lattice-based interferometer that employs an alkali Bose-Einstein condensate with a tunable scattering length. The different behavior we observe for two different orientations of the dipoles gives us evidence of the anisotropic character of the interaction. The experiment is correctly reproduced by a model we develop only if the long-range interaction between different lattice sites is taken into account. Our model indicates that dipolar interaction can be compensated by a proper choice of the scattering length and that the magnetic dipole interaction should not represent an obstacle for atom interferometry with Bose-Einstein condensates with a tunable interaction. PMID:19113248

  1. The DARPA HUMS program: revolutionizing magnetic field sensors using multiferroic materials and atomic gas vapor cells

    NASA Astrophysics Data System (ADS)

    Coblenz, William S.; Wartenberg, Scott A.

    2012-06-01

    The Heterostructural Uncooled Magnetic Sensors (HUMS) program sponsored by the Defense Advanced Research Projects Agency (DARPA/DSO) is focused on developing magnetic field sensors that operate at room temperature with an ultra-sensitivity to enable applications such as through-wall imaging, perimeter fences, tagging/tracking, and other man-portable operations. Four teams of researchers are participating in the program, with Virginia Tech and University of Maryland leading multiferroic heterostructural materials development and Princeton University and the National Institute of Standards and Technology (NIST) leading atomic vapor cell development. Leveraging the strengths of these two technologies, each team has made advancements towards the program goal of ground-breaking sensitivity, reduced noise, and portability while operating under room temperature conditions. This paper summarizes the program's achievements so far and highlights the accomplishments made by each team.

  2. Magnetic Dipolar Interaction in a Bose-Einstein Condensate Atomic Interferometer

    SciTech Connect

    Fattori, M.; Roati, G.; D'Errico, C.; Inguscio, M.; Modugno, G.; Deissler, B.; Zaccanti, M.; Jona-Lasinio, M.; Santos, L.

    2008-11-07

    We study the role played by the magnetic dipole interaction in the decoherence of a lattice-based interferometer that employs an alkali Bose-Einstein condensate with a tunable scattering length. The different behavior we observe for two different orientations of the dipoles gives us evidence of the anisotropic character of the interaction. The experiment is correctly reproduced by a model we develop only if the long-range interaction between different lattice sites is taken into account. Our model indicates that dipolar interaction can be compensated by a proper choice of the scattering length and that the magnetic dipole interaction should not represent an obstacle for atom interferometry with Bose-Einstein condensates with a tunable interaction.

  3. Quantum anomalous Hall effect in atomic crystal layers from in-plane magnetization

    NASA Astrophysics Data System (ADS)

    Ren, Yafei; Zeng, Junjie; Deng, Xinzhou; Yang, Fei; Pan, Hui; Qiao, Zhenhua

    2016-08-01

    We theoretically demonstrate that with in-plane magnetization, the quantum anomalous Hall effect (QAHE) can be realized in two-dimensional atomic crystal layers with preserved inversion symmetry but broken out-of-plane mirror reflection symmetry. By taking the honeycomb lattice system as an example, we find that the low-buckled structure satisfying the symmetry criteria is crucial to induce QAHE. The topologically nontrivial bulk gap carrying a Chern number of C =±1 opens in the vicinity of the saddle points M , where the band dispersion exhibits strong anisotropy. We further show that the QAHE with electrically tunable Chern number can be achieved in Bernal-stacked multilayer systems, and the applied interlayer potential differences can dramatically decrease the critical magnetization to make the QAHE experimentally feasible.

  4. Temperature-dependent magnetic properties of Ni nanotubes synthesized by atomic layer deposition.

    PubMed

    Pereira, Alejandro; Palma, Juan L; Denardin, Juliano C; Escrig, Juan

    2016-08-26

    Highly-ordered and conformal Ni nanotube arrays were prepared by combining atomic layer deposition (ALD) in a porous alumina matrix with a subsequent thermal reduction process. In order to obtain NiO tubes, one ALD NiCp2/O3 cycle was repeated 2000 times. After the ALD process, the sample is reduced from NiO to metallic Ni under hydrogen atmosphere. Their magnetic properties such as coercivity and squareness have been determined in a vibrating sample magnetometer in the temperature range from 5-300 K for applied magnetic fields parallel and perpendicular to the nanotube axis. Ni nanotubes synthesized by ALD provide a promising opportunity for potential applications in spintronics, data storage and bio-applications. PMID:27454022

  5. Temperature-dependent magnetic properties of Ni nanotubes synthesized by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Pereira, Alejandro; Palma, Juan L.; Denardin, Juliano C.; Escrig, Juan

    2016-08-01

    Highly-ordered and conformal Ni nanotube arrays were prepared by combining atomic layer deposition (ALD) in a porous alumina matrix with a subsequent thermal reduction process. In order to obtain NiO tubes, one ALD NiCp2/O3 cycle was repeated 2000 times. After the ALD process, the sample is reduced from NiO to metallic Ni under hydrogen atmosphere. Their magnetic properties such as coercivity and squareness have been determined in a vibrating sample magnetometer in the temperature range from 5–300 K for applied magnetic fields parallel and perpendicular to the nanotube axis. Ni nanotubes synthesized by ALD provide a promising opportunity for potential applications in spintronics, data storage and bio-applications.

  6. Dependence of Berry's phase for atom on a sign of the g factor in the rotating magnetic field

    SciTech Connect

    Morinaga, Atsuo; Aoki, Takatoshi; Yasuhara, Makoto

    2005-05-15

    Berry's phase of the atom in the state with a positive or negative g factor for partial cycles of a rotating magnetic field was determined free from the dynamical phase shift using a time-domain atom interferometer. The experimental phase shift is in good agreement with the prediction of Berry's phase for partial cycles. It was found that the sense of Berry's phase depends on the sign of the magnetic quantum number, the sense of the rotating magnetic field, and the sign of the g factor of the state.

  7. Structures and magnetic properties of Pd{sub n} clusters (n=3-19) doped by Mn atoms

    SciTech Connect

    Mu Yuewen; Han Yan; Wan Jianguo; Wang Guanghou; Wang Jinlan

    2011-11-15

    The structures and magnetic properties of Pd{sub n} and Pd{sub n-1}Mn clusters (n = 3-19) are investigated by using a spin-polarized density functional theory approach. Several different lowest-energy structures of Pd{sub n} clusters (n 11, 12, 14, 17) are found. It is shown that when a Mn atom is doped into the Pd{sub n} cluster, the cluster structure does not change for n < 9, while Mn doping gives rise to a geometry reconstruction for n > 9. The doping of a Mn atom enhances the stability of Pd{sub n} clusters and increases their magnetic moment by a magnitude of (3-5){mu}{sub B}. Moreover, we observe an evident oscillation of steplike magnetic behavior in Pd{sub n} clusters upon doping of a Mn atom, and the origin of such a magnetic phenomenon is analyzed in detail.

  8. Large perpendicular magnetic anisotropy of single Co atom on MgO monolayer: A first-principles study

    SciTech Connect

    Shao, Bin; Shi, Wu-Jun; Feng, Min; Zuo, Xu

    2015-05-07

    Realizing the magnetic bit with a single atom is the ultimate goal for magnetic storage. Based on density functional theory, the magnetic anisotropy (MA) of single Co atom on MgO monolayer has been investigated. Results show that this two dimensional system possesses a large perpendicular MA, about 5.8 meV per Co atom. Besides, there exists remarkable unquenched orbital moments for different magnetization directions, which can be attributed to the reduction of coordination number in two dimensional system and is responsible for the enhanced MA. The Bloch pseudo-wavefunction and band structure of Co d-orbitals have been calculated to elucidate the origin of the perpendicular MA.

  9. Conductive Atomic Force Microscopy Analysis of Sub-30 nm Magnetic Tunnel Junction Nanopillars

    NASA Astrophysics Data System (ADS)

    Evarts, Eric R.

    2011-12-01

    At the nanoscale, physical processes can be found that do not have a macroscopic counterpart. The electrical manipulation of nanomagnets is an example of one such process that has no measurable effect in structures larger than a few micrometers. For nanomagnets less than 50 nm across, there was no existing technique that could reliably detect and manipulate these nanomagnets. I present here a conductive atomic force microscopy (CAFM) technique that can deliver greater than 10 mA of current to a magnetic nanopillar as small as 10 nm in diameter. Using magnetic tunnel junction (MTJ) nanopillars with two thin ferromagnetic layers separated by a thin insulator, two different electrical resistances are measured for the parallel and antiparallel relative magnetic orientations. Using this technique, I demonstrated spin torque transfer (STT) switching of MTJ nanopillars. Using nanoparticle masking, I fabricated smaller MTJ nanopillars than previously reported. These 26 nm diameter MTJ nanopillars showed an increased switching current density of 10 × 10 6 A/cm2 compared to the 1-3 × 106 A/cm2 observed on 200 nm × 100 nm nanopillars. As these small nanopillars were cycled multiple times, the electrical and magnetic properties changed showing a decrease in the ΔR between the two states and an overall increase in the resistance indicating a shrinking effective nanopillar diameter due to oxidation. The low frequency noise power spectrum was recorded as a function of applied current density. These spectra indicate a small magnetic noise component that depends on the STT effect that can be suppressed with an applied magnetic field.

  10. Nonclassical Properties for Two Coupled N-Two-Level Atom and a Single Two-Level Atom Under an External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Abdalla, M. Sebawe; Ahmed, M. M. A.; Rabea, R. N.

    2016-06-01

    We study the interaction between a single two-level atom and N two-level atoms under the effect of a uniform magnetic field. The exact solution is obtained and the expectation value of the time-dependent quantum operators calculated using the Block state (the generalized coherent state). We discuss numerically the atomic inversion where the phenomenon of collapse and revival is observed. The change in the value of the atomic angle plays a role in variance squeezing, where it is pronounced for 𝜃 = π/3. Entropy squeezing is discussed and occurred in the first quadrature. The degree of entanglement through linear entropy is examined where the system shows partial entanglement and at a certain value of parameters displays nearly maximum entanglement.

  11. Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.

    2016-05-01

    Hyperfine-induced electric dipole contributions may significantly increase probabilities of otherwise very weak electric octupole and magnetic quadrupole atomic clock transitions (e.g., transitions between s and f electron orbitals). These transitions can be used for exceptionally accurate atomic clocks, quantum information processing, and the search for dark matter. They are very sensitive to new physics beyond the standard model, such as temporal variation of the fine-structure constant, the Lorentz invariance, and Einstein equivalence principle violation. We formulate conditions under which the hyperfine-induced electric dipole contribution dominates and perform calculations of the hyperfine structure and E3, M2 and the hyperfine-induced E1 transition rates for a large number of atoms and ions of experimental interest. Due to the hyperfine quenching the electric octupole clock transition in +173Yb is 2 orders of magnitude stronger than that in currently used +171Yb. Some enhancement is found in 13+143Nd, 14+149Pm, 14+147Sm, and 15+147Sm ions.

  12. Visualization of Ce atoms and surface-induced magnetism in CeCoIn5

    NASA Astrophysics Data System (ADS)

    Yoshida, Yasuo; Kim, Howon; Lee, Chi-Cheng; Lin, Hsin; Haga, Yoshinori; Tateiwa, Naoyuki; Fisk, Zachary; Hasegawa, Yukio

    CeCoIn5 is known as a heavy fermion compound naturally born at the quantum critical point having an unconventional d-wave superconducting phase at low temperatures. Recently, several STM works on a cleaved surface of this compound reported visualization of emerging heavy fermion bands and consistency of the bulk superconducting properties reported previously. However, reported STM images in those works only visualized In atoms on the Ce-In plane even though the Ce-In plane contains Ce and In atoms. By performing precise low-temperature STM measurements on CeCoIn5, we successfully visualize Ce atoms on the Ce-In plane and, in addition, surface-induced staggered dumbblell-shaped order on the Co plane. This ordered structure locally has C2v symmetry but retaining C4 symmetry. This structure coexists with the superconductivity, and is robust against temperatures (>Tc) and an external magnetic field (>Hc2) . In the talk, we will discuss the origin of the peculiar ordered structure based on our experimental observations together with first principles calculations.

  13. Achievement of high atomic hydrogen densities in cylindrical rf plasmas with magnetic field

    NASA Astrophysics Data System (ADS)

    Fantz, Ursel; Briefi, Stefan

    2014-10-01

    Cylindrical rf plasmas in hydrogen with and without an axial magnetic field of up to 120 G are investigated in the pressure range of 0.3 to 10 Pa. The atomic hydrogen density is determined with optical emission spectroscopy, analyzing the Balmer lines and the molecular radiation (Fulcher band). The results obtained by using different coil geometries (4 to 6 turn windings and Nagoya type antenna) as well as different diameters (10 cm and 25 cm) of a quartz, aluminum oxide or aluminum nitride cylinder are compared. RF powers of up to 600 W at a frequency of 13.56 MHz are available for the 10 cm configuration, whereas up to 70 kW power at 1 MHz are used for the 25 cm cylinder. Density ratios of atoms to molecules of up to 0.3 are achieved in both configurations, whereby the achievement in the high power setup is limited by neutral depletion. The influence of the wall material on the atomic densities, and thus the recombination coefficient, will be pointed out.

  14. Strong-field atomic ionization in an elliptically polarized laser field and a constant magnetic field

    NASA Astrophysics Data System (ADS)

    Rylyuk, V. M.

    2016-05-01

    Within the framework of the quasistationary quasienergy state (QQES) formalism, the tunneling and multiphoton ionization of atoms and ions subjected to a perturbation by a high intense laser radiation field of an arbitrary polarization and a constant magnetic field are considered. On the basis of the exact solution of the Schrödinger equation and the Green's function for the electron moving in an arbitrary laser field and crossed constant electric and magnetic fields, the integral equation for the complex quasienergy and the energy spectrum of the ejected electron are derived. Using the "imaginary-time" method, the extremal subbarrier trajectory of the photoelectron moving in a nonstationary laser field and a constant magnetic field are considered. Within the framework of the QQES formalism and the quasiclassical perturbation theory, ionization rates when the Coulomb interaction of the photoelectron with the parent ion is taken into account at arbitrary values of the Keldysh parameter are derived. The high accuracy of rates is confirmed by comparison with the results of numerical calculations. Simple analytical expressions for the ionization rate with the Coulomb correction in the tunneling and multiphoton regimes in the case of an elliptically polarized laser beam propagating at an arbitrary angle to the constant magnetic field are derived and discussed. The limits of small and large magnetic fields and low and high frequency of a laser field are considered in details. It is shown that in the presence of a nonstationary laser field perturbation, the constant magnetic field may either decrease or increase the ionization rate. The analytical consideration and numerical calculations also showed that the difference between the ionization rates for an s electron in the case of right- and left-elliptically polarized laser fields is especially significant in the multiphoton regime for not-too-high magnetic fields and decreases as the magnetic field increases. The paper

  15. Magnetism and electronic phase transitions in monoclinic transition metal dichalcogenides with transition metal atoms embedded

    NASA Astrophysics Data System (ADS)

    Lin, Xianqing; Ni, Jun

    2016-08-01

    First-principles calculations have been performed to study the energetic, electronic, and magnetic properties of substitutional 3d transition metal dopants in monoclinic transition metal dichalcogenides (TMDs) as topological insulators ( 1 T ' - MX 2 with M = (Mo, W) and X = (S, Se)). We find various favorite features in these doped systems to introduce magnetism and other desirable electronic properties: (i) The Mn embedded monoclinic TMDs are magnetic, and the doped 1 T ' - MoS 2 still maintains the semiconducting character with high concentration of Mn, while an electronic phase transition occurs in other Mn doped monoclinic TMDs with an increasing concentration of Mn. Two Mn dopants prefer the ferromagnetic coupling except for substitution of the nearest Mo atoms in 1 T ' - MoS 2 , and the strength of exchange interaction shows anisotropic behavior with dopants along one Mo zigzag chain having much stronger coupling. (ii) The substitutional V is a promising hole dopant, which causes little change to the energy dispersion around the conduction and valence band edges in most systems. In contrast, parts of the conduction band drop for the electron dopants Co and Ni due to the large structural distortion. Moreover, closing band gaps of the host materials are observed with increasing carrier concentration. (iii) Single Fe dopant has a magnetic moment, but it also dopes electrons. When two Fe dopants have a small distance, the systems turn into nonmagnetic semiconductors. (iv) The formation energies of all dopants are much lower than those in hexagonal TMDs and are all negative in certain growth conditions, suggesting possible realization of the predicted magnetism, electronic phase transitions as well as carrier doping in 1 T ' - MX 2 based topological devices.

  16. Ground state of Ho atoms on Pt(111) metal surfaces: Implications for magnetism

    NASA Astrophysics Data System (ADS)

    Karbowiak, M.; Rudowicz, C.

    2016-05-01

    We investigated the ground state of Ho atoms adsorbed on the Pt(111) surface, for which conflicting results exist. The density functional theory (DFT) calculations yielded the Ho ground state as | Jz=±8 > . Interpretation of x-ray absorption spectroscopy and x-ray magnetic circular dichroism spectra and the magnetization curves indicated the ground state as | Jz=±6 > . Superposition model is employed to predict the crystal-field (CF) parameters based on the structural data for the system Ho/Pt(111) obtained from the DFT modeling. Simultaneous diagonalization of the free-ion (HFI) and the trigonal CF Hamiltonian (HCF) within the whole configuration 4 f10 of H o3 + ion was performed. The role of the trigonal CF terms, neglected in the pure uniaxial CF model used previously for interpretation of experimental spectra, is found significant, whereas the sixth-rank CF terms may be neglected in agreement with the DFT predictions. The results provide substantial support for the experimental designation of the | Jz=±6 > ground state, albeit with subtle difference due to admixture of other | Jz> states, but run against the DFT-based designation of the | Jz=±8 > ground state. A subtle splitting of the ground energy level with the state (predominantly), | Jz=±6 > is predicted. This paper provides better insight into the single-ion magnetic behavior of the Ho/Pt(111) system by helping to resolve the controversy concerning the Ho ground state. Experimental techniques with greater resolution powers are suggested for direct confirmation of this splitting and C3 v symmetry experienced by the Ho atom.

  17. Coherent manipulation of a single magnetic atom using polarized single electron transport in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Lai, Wenxi; Yang, Wen

    2015-10-01

    We consider theoretically a magnetic impurity spin driven by polarized electrons tunneling through a double-quantum-dot system. The spin-blockade effect and spin conservation in the system make the magnetic impurity sufficiently interact with each transferring electron. As a result, a single collected electron carries information about spin change of the magnetic impurity. The scheme may develop all-electrical manipulation of magnetic atoms by means of single electrons, which is significant for the implementation of scalable logical gates in information processing systems.

  18. Heavy atom effect on magnetic anisotropy of matrix-isolated monobromine substituted septet trinitrene.

    PubMed

    Misochko, Eugenii Ya; Masitov, Artem A; Akimov, Alexander V; Korchagin, Denis V; Chapyshev, Sergei V

    2015-03-19

    The heavy atom effect on the magnetic anisotropy of septet trinitrenes is reported. Septet 1-bromo-3,5-dichloro-2,4,6-trinitrenobenzene (S-1) was generated in a solid argon matrix by ultraviolet irradiation of 1,3,5-triazido-2-bromo-4,6-dichlorobenzene. This trinitrene displays an electron spin resonance (ESR) spectrum that drastically differs from ESR spectra of all previously studied septet trinitrenes. The zero-field splitting (ZFS) parameters, derived from the experimental spectrum, show the parameter |D| = 0.1237 cm(-1) and the unprecedentedly large ratio of E/D = 0.262 that is close to the rhombic limit E/D = 1/3 for high-spin molecules. The CASCI (based on state-averaged CASSCF) and DFT methods were applied to calculate the ZFS tensor focusing on the heavy (bromine) atom effects on the spin-orbit term. These calculations show that the multiconfigurational ab initio formalism and the CASCI method are the most successful for accurate predictions of the spin-orbit term in the ZFS tensor of high-spin nitrenes containing heavy bromine atoms. Due to the presence of the bromine atom in S-1, the contribution of the spin-orbit term to the total parameter D is dominant and responsible for the unusual orientation of the easy Z-axis lying in the molecular plane perpendicular to the C-Br bond. As a result, the principal values D(XX), D(YY), and D(ZZ) of the total tensor D̂(Tot) have such magnitudes and signs for which the ratio E/D is close to the rhombic limit, and the total parameter D is large in magnitude and positive in sign. PMID:25350487

  19. Scattering amplitude of ultracold atoms near the p-wave magnetic Feshbach resonance

    SciTech Connect

    Zhang Peng; Naidon, Pascal; Ueda, Masahito

    2010-12-15

    Most of the current theories on the p-wave superfluid in cold atomic gases are based on the effective-range theory for the two-body scattering, where the low-energy p-wave scattering amplitude f{sub 1}(k) is given by f{sub 1}(k)=-1/[ik+1/(Vk{sup 2})+1/R]. Here k is the incident momentum, V and R are the k-independent scattering volume and effective range, respectively. However, due to the long-range nature of the van der Waals interaction between two colliding ultracold atoms, the p-wave scattering amplitude of the two atoms is not described by the effective-range theory [J. Math. Phys. 4, 54 (1963); Phys. Rev. A 58, 4222 (1998)]. In this paper we provide an explicit calculation for the p-wave scattering of two ultracold atoms near the p-wave magnetic Feshbach resonance. We show that in this case the low-energy p-wave scattering amplitude f{sub 1}(k)=-1/[ik+1/(V{sup eff}k{sup 2})+1/(S{sup eff}k)+1/R{sup eff}] where V{sup eff}, S{sup eff}, and R{sup eff} are k-dependent parameters. Based on this result, we identify sufficient conditions for the effective-range theory to be a good approximation of the exact scattering amplitude. Using these conditions we show that the effective-range theory is a good approximation for the p-wave scattering in the ultracold gases of {sup 6}Li and {sup 40}K when the scattering volume is enhanced by the resonance.

  20. Atomic structure of the i-R -Cd quasicrystals and consequences for magnetism

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Takakura, H.; Kong, T.; Das, P.; Jayasekara, W. T.; Kreyssig, A.; Beutier, G.; Canfield, P. C.; de Boissieu, M.; Goldman, A. I.

    2016-08-01

    We report on the six-dimensional (6D) structural refinement of three members of the i-R -Cd quasicrystals (R = Gd, Dy, Tm) via synchrotron x-ray diffraction from single-grain samples, and show that this series is isostructural to the i-YbCd5.7 quasicrystal. However, our refinements suggest that the R occupancy on the Yb icosahedron sites within the Tsai-type atomic cluster is approximately 80%, with the balance taken up by Cd. Similarities between the i-R -Cd series and i-ScZn7.33, and their differences with i-YbCd5.7 and i-Ca15Cd85 , indicate that there are at least two subclasses of Tsai-type icosahedral quasicrystals. We further show from x-ray resonant magnetic scattering (XRMS) measurements on a set of closely related Tb1 -xYxCd6 1/1 approximants that the dilution of the magnetic R ions on the icosahedron within the Tsai-type cluster by nonmagnetic Y disrupts the commensurate magnetic ordering in the approximant phase.

  1. Giant modification of atomic transition probabilities induced by a magnetic field: forbidden transitions become predominant

    NASA Astrophysics Data System (ADS)

    Sargsyan, Armen; Tonoyan, Ara; Hakhumyan, Grant; Papoyan, Aram; Mariotti, Emilio; Sarkisyan, David

    2014-05-01

    The magnetic field-induced giant modification of probabilities for seven components of 6S1/2, Fg = 3 → 6P3/2, Fe = 5 transition of the Cs D2 line, forbidden by selection rules, is observed experimentally for the first time. For the case of excitation with circularly polarized laser radiation, the probability of a Fg = 3, mF = -3 → Fe = 5, mF = -2 transition becomes the largest of 25 transitions of the Fg = 3 → Fe = 2,3,4,5 group in a wide-range magnetic field of 200-3200 G. Moreover, the modification is the largest among D2 lines of alkali metals. A half-wave-thick cell (the length along the beam propagation axis L = 426 nm) filled with Cs has been used in order to achieve sub-Doppler resolution, which allows the large number of atomic transitions that appear in the absorption spectrum to be separated when an external magnetic field is applied. For B > 3000 G the group of seven transitions Fg = 3 → Fe = 5 is completely resolved and is located at the high frequency level of Fg= 3 → Fe = 2,3,4 transitions. The applied theoretical model describes very well the experimental curves.

  2. Anomalous magnetic hyperfine structure of the 229Th ground-state doublet in muonic atoms

    NASA Astrophysics Data System (ADS)

    Tkalya, E. V.

    2016-07-01

    The magnetic hyperfine (MHF) splitting of the ground and low-energy 3 /2+(7.8 ±0.5 eV) levels in the 229Th nucleus in the muonic atom (μ1S1 /2 -229Th) * is calculated considering the distribution of the nuclear magnetization in the framework of the collective nuclear model with wave functions of the Nilsson model for the unpaired neutron. It is shown that (a) deviation of the MHF structure of the isomeric state exceeds 100% from its value for a pointlike nuclear magnetic dipole (the order of sublevels is reversed); (b) partial inversion of levels of the 229Th ground-state doublet and spontaneous decay of the ground state to the isomeric state occur; (c) the E 0 transition, which is sensitive to differences in the mean-square charge radii of the doublet states, is possible between mixed sublevels with F =2 ; and (d) MHF splitting of the 3 /2+ isomeric state may be in the optical range for certain values of the intrinsic gK factor and a reduced probability of a nuclear transition between the isomeric and the ground states.

  3. Effect of projection velocity and temperature on the reflection of ultracold atoms from a periodic one-dimensional corrugated magnetic potential

    SciTech Connect

    Singh, Mandip; Hannaford, Peter

    2010-07-15

    The spatial profile of ultracold atoms reflecting from an exponentially decaying magnetic potential depends on parameters such as the corrugation in the magnetic potential and the temperature of the atomic cloud. We report on experimental investigations of the effect of projection velocity which determines the strength of the interaction of the atom cloud with the magnetic potential and the effect of temperature of ultracold {sup 87}Rb atoms reflecting from a periodic one-dimensional corrugated magnetic potential. The magnetic potential is generated on an atom chip by a periodic permanent magnetic structure of period 10 {mu}m. The amplitude of the corrugation is controlled by applying a uniform external-bias magnetic field.

  4. RHIC warm-bore systems

    SciTech Connect

    Welch, K.M.

    1994-07-01

    Pressure profiles, in time, are calculated as a consequence of anticipated outgassing of various beam components (e.g., rf cavities, etc.) and warm-bore beam pipes. Gold beam lifetimes and transverse beam emittance growth are given for calculated average pressures. Examples of undesirable warm-bore conditions are presented such as contaminated experimental beam pipes and warm-bore magnets (i.e., DX). These examples may prove instructive. The methods used in making these calculations are presented in Section 2. They are applicable to all linear systems. The calculations given apply to the RHIC accelerator and more specifically to warm-bore regions of the machine.

  5. Atomic disorder and the magnetic, electrical, and optical properties of a Co{sub 2}CrAl Heusler alloy

    SciTech Connect

    Svyazhin, A. D. Shreder, E. I.; Voronin, V. I.; Berger, I. F.; Danilov, S. E.

    2013-03-15

    Two Co{sub 2}CrAl alloy samples subjected to different heat treatment regimes are studied. An exact distribution of atoms over the sublattices in the samples is determined by X-ray diffraction and neutron diffraction methods. These data are used to perform ab initio density of states calculations and to calculate the magnetic moments of the samples in a coherent potential approximation. The calculated magnetic moments are compared to the experimental values. The effect of atomic ordering on the electronic structure near the Fermi level is analyzed using optical methods. The possible causes of the detected temperature dependence of the electrical resistivity, unusual for metallic alloys, are discussed.

  6. Magnetic states of Mn and Co atoms at Co2MnGe/MgO interfaces seen via soft x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Asakura, D.; Koide, T.; Yamamoto, S.; Tsuchiya, K.; Shioya, T.; Amemiya, K.; Singh, V. R.; Kataoka, T.; Yamazaki, Y.; Sakamoto, Y.; Fujimori, A.; Taira, T.; Yamamoto, M.

    2010-11-01

    The magnetic states of Mn and Co atoms in Co-rich Co2MnGe Heusler alloy thin films facing an MgO barrier were studied by means of soft x-ray magnetic circular dichroism (XMCD). In particular, the Co2MnGe film-thickness dependence of the Mn and Co magnetic moments was investigated. With a decrease in the Co2MnGe film thickness to 1-2 monolayers (MLs), the spin magnetic moment of Mn decreased and the MnL2,3 -edge x-ray absorption spectra (XAS) showed a Mn2+ -like multiplet structure in MnO, in contrast to samples thicker than 4 ML, indicating that the Mn atoms of the 1 and 2 ML samples were oxidized. The Co spin magnetic moment increased slightly with decreasing thickness. A Co2+ -like multiplet structure in CoO was not observed in all the CoL2,3 -edge XAS and XMCD, indicating that, even in the ultrathin samples, the Co atoms were not oxidized, and were more strongly spin polarized than those in the thicker samples. Co spin magnetic moments of 1.40-1.77μB larger than the theoretical value for ideal stoichiometric Co2MnGe (˜1μB) and the Co-rich film composition imply the presence of Co antisites that would lower the spin polarization.

  7. Quantum and Classical Description of H Atom Under Magnetic Field and Quadrupole Trap Potential

    SciTech Connect

    Mahecha, J.; Salas, J. P.

    2006-12-01

    A discussion regarding the energy levels spectrum of quantum systems whose classical analogous has states of chaotic motion is presented. The chaotic dynamics of the classical underlying system has its manifestation in the wave functions (in the form of 'scars') and in the energy levels (in the form of 'statistical repulsion' of the energy levels). The above mentioned signatures are named 'quantum chaos'. A typical study of quantum chaos requires finding accurate energy eigenvalues of highly excited states, to calculate the nearest neighbors spacing between levels, to perform the 'unfolding' of the spectrum in order to separate the fluctuations, and finally to find the probability distribution of the unfolded spectrum. This is exemplified by the hydrogen atom under uniform magnetic field and a quadrupole electric field.

  8. Magnetically controlled exchange process in an ultracold atom-dimer mixture.

    PubMed

    Knoop, S; Ferlaino, F; Berninger, M; Mark, M; Nägerl, H-C; Grimm, R; D'Incao, J P; Esry, B D

    2010-02-01

    We report on the observation of an elementary exchange process in an optically trapped ultracold sample of atoms and Feshbach molecules. We can magnetically control the energetic nature of the process and tune it from endoergic to exoergic, enabling the observation of a pronounced threshold behavior. In contrast to relaxation to more deeply bound molecular states, the exchange process does not lead to trap loss. We find excellent agreement between our experimental observations and calculations based on the solutions of three-body Schrödinger equation in the adiabatic hyperspherical representation. The high efficiency of the exchange process is explained by the halo character of both the initial and final molecular states. PMID:20366759

  9. Magnetically-modulated atomic force microscopy for analysis of soft matter systems.

    PubMed

    Kageshima, Masami

    2012-11-01

    Experimental method of studying viscoelasticity, a common idea to understand properties of microscopic biological soft matter systems, especially single biopolymer chains, using atomic force microscopy (AFM) with magnetically- driven cantilever is surveyed. The experimental setup of applying well-characterized excitation to the cantilever and the analysis method to derive the viscoelasticity of the system under study are briefly introduced. Examples of measuring viscoelasticity of single peptide molecule and single titin molecule are shown. Considering the close relation of viscoelasticity and the time-scale for nonequilibrium dynamics in soft matter, extension of the method to a frequency-resolved analysis is attempted. A result of measuring viscoelasticity spectrum of a single dextran chain is shown. Challenges in further progress of the method are also described. PMID:22039807

  10. Atomic force microscopy-coupled microcoils for cellular-scale nuclear magnetic resonance spectroscopy

    PubMed Central

    Mousoulis, Charilaos; Maleki, Teimour; Ziaie, Babak; Neu, Corey P.

    2013-01-01

    We present the coupling of atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) technologies to enable topographical, mechanical, and chemical profiling of biological samples. Here, we fabricate and perform proof-of-concept testing of radiofrequency planar microcoils on commercial AFM cantilevers. The sensitive region of the coil was estimated to cover an approximate volume of 19.4 × 103 μm3 (19.4 pl). Functionality of the spectroscopic module of the prototype device is illustrated through the detection of 1Η resonance in deionized water. The acquired spectra depict combined NMR capability with AFM that may ultimately enable biophysical and biochemical studies at the single cell level. PMID:24719493

  11. Structural, electronic, and magnetic properties of heterofullerene C(58)Si with odd number of atoms and a near planar tetracoordinate Si atom.

    PubMed

    Liu, Feng-Ling; Jalbout, Abraham F

    2008-06-01

    Density functional calculations and minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C(58)Si-C(2v). Since it has odd number of atoms and a near planar tetracoordinate Si atom on the skeleton of the cage, it has odd number of atoms assembling a cage and is a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/6-31G* level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface. Sixteen (13)C nuclear magnetic resonance (NMR) spectral signals of C(58)Si are characterized, and its heat of formation was estimated in this work. PMID:18328755

  12. Atomic-Resolution X-ray Energy-Dispersive Spectroscopy Chemical Mapping of Substitutional Dy Atoms in a High-Coercivity Neodymium Magnet

    NASA Astrophysics Data System (ADS)

    Itakura, Masaru; Watanabe, Natsuki; Nishida, Minoru; Daio, Takeshi; Matsumura, Syo

    2013-05-01

    We have investigated local element distributions in a Dy-doped Nd2Fe14B hot-deformed magnet by atomic-column resolution chemical mapping using an X-ray energy-dispersive spectrometer (XEDS) attached to an aberration-corrected scanning transmission electron microscope (Cs-corrected STEM). The positions of the Nd and Dy atomic columns were visualized in the XEDS maps. The substitution of Dy was limited to a surface layer 2-3 unit cells thick in the Nd2Fe14B grains, and the Dy atoms preferentially occupied the 4f-Nd sites of Nd2Fe14B. These results provide further insights into the principal mechanism governing the coercivity enhancement due to Dy doping.

  13. Controllable magnetic solitons excitations in an atomic chain of spinor Bose-Einstein condensates confined in an optical lattice

    NASA Astrophysics Data System (ADS)

    Zhao, Xing-Dong; Geng, Z.; Zhao, Xu; Qian, J.; Zhou, Lu; Li, Y.; Zhang, Weiping

    2014-06-01

    We propose an experimental scheme to show that the nonlinear magnetic solitary excitations can be achieved in an atomic spinor Bose-Einstein condensate confined in a blue-detuned optical lattice. Through exact theoretical calculations, we find that the magnetic solitons can be generated by the static magnetic dipole-dipole interaction (MDDI), of which the interaction range can be well controlled. We derive the existence conditions of the magnetic solitons under the nearest-neighboring, the next-nearest-neighboring approximations as well as the long-range consideration. It is shown that the long-range feature of the MDDI plays an important role in determining the existence of magnetic solitons in this system. In addition, to facilitate the experimental observation, we apply an external laser field to drive the lattice, and the existence regions for the magnetic soliton induced by the anisotropic light-induced dipole-dipole interaction are also investigated.

  14. Variational-average-atom-in-quantum-plasmas (VAAQP) code and virial theorem: Equation-of-state and shock-Hugoniot calculations for warm dense Al, Fe, Cu, and Pb

    SciTech Connect

    Piron, R.; Blenski, T.

    2011-02-15

    The numerical code VAAQP (variational average atom in quantum plasmas), which is based on a fully variational model of equilibrium dense plasmas, is applied to equation-of-state calculations for aluminum, iron, copper, and lead in the warm-dense-matter regime. VAAQP does not impose the neutrality of the Wigner-Seitz ion sphere; it provides the average-atom structure and the mean ionization self-consistently from the solution of the variational equations. The formula used for the electronic pressure is simple and does not require any numerical differentiation. In this paper, the virial theorem is derived in both nonrelativistic and relativistic versions of the model. This theorem allows one to express the electron pressure as a combination of the electron kinetic and interaction energies. It is shown that the model fulfills automatically the virial theorem in the case of local-density approximations to the exchange-correlation free-energy. Applications of the model to the equation-of-state and Hugoniot shock adiabat of aluminum, iron, copper, and lead in the warm-dense-matter regime are presented. Comparisons with other approaches, including the inferno model, and with available experimental data are given. This work allows one to understand the thermodynamic consistency issues in the existing average-atom models. Starting from the case of aluminum, a comparative study of the thermodynamic consistency of the models is proposed. A preliminary study of the validity domain of the inferno model is also included.

  15. Variational-average-atom-in-quantum-plasmas (VAAQP) code and virial theorem: equation-of-state and shock-Hugoniot calculations for warm dense Al, Fe, Cu, and Pb.

    PubMed

    Piron, R; Blenski, T

    2011-02-01

    The numerical code VAAQP (variational average atom in quantum plasmas), which is based on a fully variational model of equilibrium dense plasmas, is applied to equation-of-state calculations for aluminum, iron, copper, and lead in the warm-dense-matter regime. VAAQP does not impose the neutrality of the Wigner-Seitz ion sphere; it provides the average-atom structure and the mean ionization self-consistently from the solution of the variational equations. The formula used for the electronic pressure is simple and does not require any numerical differentiation. In this paper, the virial theorem is derived in both nonrelativistic and relativistic versions of the model. This theorem allows one to express the electron pressure as a combination of the electron kinetic and interaction energies. It is shown that the model fulfills automatically the virial theorem in the case of local-density approximations to the exchange-correlation free-energy. Applications of the model to the equation-of-state and Hugoniot shock adiabat of aluminum, iron, copper, and lead in the warm-dense-matter regime are presented. Comparisons with other approaches, including the inferno model, and with available experimental data are given. This work allows one to understand the thermodynamic consistency issues in the existing average-atom models. Starting from the case of aluminum, a comparative study of the thermodynamic consistency of the models is proposed. A preliminary study of the validity domain of the inferno model is also included. PMID:21405914

  16. Warm ISM in the Sagittarius A Complex. I. Mid-J CO, atomic carbon, ionized atomic carbon, and ionized nitrogen sub-mm/FIR line observations with the Herschel-HIFI and NANTEN2/SMART telescopes

    NASA Astrophysics Data System (ADS)

    García, P.; Simon, R.; Stutzki, J.; Güsten, R.; Requena-Torres, M. A.; Higgins, R.

    2016-04-01

    Aims: We investigate the spatial and spectral distribution of the local standard of rest (LSR) velocity resolved submillimetre emission from the warm (25-90 K) gas in the Sgr A Complex, located in the Galactic centre. Methods: We present large-scale submillimetre heterodyne observations towards the Sgr A Complex covering ~300 arcmin2. These data were obtained in the frame of the Herschel EXtraGALactic guaranteed time key program (HEXGAL) with the Herschel-HIFI satellite and are complemented with submillimetre observations obtained with the NANTEN2/SMART telescope as part of the NANTEN2/SMART Central Nuclear Zone Survey. The observed species are CO(J = 4-3) at 461.0 GHz observed with the NANTEN2/SMART telescope, and [CI] 3P1-3P0 at 492.2 GHz, [CI] 3P2-3P1 at 809.3 GHz, [NII] 3P1-3P0 at 1461.1 GHz, and [CII] 2P3/2-2P1/2 at 1900.5 GHz observed with the Herschel-HIFI satellite. The observations are presented in a 1 km s-1 spectral resolution and a spatial resolution ranging from 46 arcsec to 28 arcsec. The spectral coverage of the three lower frequency lines is ±200 km s-1, while in the two high frequency lines, the upper LSR velocity limit is +94 km s-1 and +145 km s-1 for the [NII] and [CII] lines, respectively. Results: The spatial distribution of the emission in all lines is very widespread. The bulk of the carbon monoxide emission is found towards Galactic latitudes below the Galactic plane, and all the known molecular clouds are identified. Both neutral atomic carbon lines have their brightest emission associated with the +50 km s-1 cloud. Their spatial distribution at this LSR velocity describes a crescent-shape structure, which is probably the result of interaction with the energetic event (one or several supernovae explosions) that gave origin to the non-thermal Sgr A-East source. The [CII] and [NII] emissions have most of their flux associated with the thermal arched-filaments and the H region and bright spots in [CII] emission towards the central nuclear

  17. Rovibrational molecular populations, atoms, and negative ions in H2 and D2 magnetic multicusp discharges

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J.-P. E.; Bacal, M.; Hillion, F.

    1985-06-01

    Coherent anti-Stokes Raman scattering is applied to the study of rovibrational populations in magnetic multicusp H2 and D2 discharges. This subject is of interest to negative hydrogen-ion formation by volume plasma processes. The populations of high-lying rotational states (J greater than 5) in the vibrational levels v = 0, 1, and 2 are found to be significantly higher than expected from the Boltzmann law. In H2 the net populations of the first four vibrational levels follow approximately the Boltzmann law, with the vibrational temperature of 2390 K (in a 90 V-10 A discharge at 55 micro bar). In similar discharge conditions, the population of the state v = 3 in D2 is higher than expected from the Boltzmann law. In the presence of the discharge a deficiency in H2 and D2 molecule density was observed and was attributed to the possible presence of H and D atoms. This was verified by an independent measurement of the atomic fraction and temperature. The density of negative ions, measured by the photodetachment technique, is also reported.

  18. Benchmarking atomic physics models for magnetically confined fusion plasma physics experiments

    NASA Astrophysics Data System (ADS)

    May, M. J.; Finkenthal, M.; Soukhanovskii, V.; Stutman, D.; Moos, H. W.; Pacella, D.; Mazzitelli, G.; Fournier, K.; Goldstein, W.; Gregory, B.

    1999-01-01

    In present magnetically confined fusion devices, high and intermediate Z impurities are either puffed into the plasma for divertor radiative cooling experiments or are sputtered from the high Z plasma facing armor. The beneficial cooling of the edge as well as the detrimental radiative losses from the core of these impurities can be properly understood only if the atomic physics used in the modeling of the cooling curves is very accurate. To this end, a comprehensive experimental and theoretical analysis of some relevant impurities is undertaken. Gases (Ne, Ar, Kr, and Xe) are puffed and nongases are introduced through laser ablation into the FTU tokamak plasma. The charge state distributions and total density of these impurities are determined from spatial scans of several photometrically calibrated vacuum ultraviolet and x-ray spectrographs (3-1600 Å), the multiple ionization state transport code transport code (MIST) and a collisional radiative model. The radiative power losses are measured with bolometery, and the emissivity profiles were measured by a visible bremsstrahlung array. The ionization balance, excitation physics, and the radiative cooling curves are computed from the Hebrew University Lawrence Livermore atomic code (HULLAC) and are benchmarked by these experiments. (Supported by U.S. DOE Grant No. DE-FG02-86ER53214 at JHU and Contract No. W-7405-ENG-48 at LLNL.)

  19. Specific features of the formation of atomic magnetic moments in amorphous films RE-Co ( RE = La, Gd, Tb)

    NASA Astrophysics Data System (ADS)

    Vas'kovskiy, V. O.; Adanakova, O. A.; Balymov, K. G.; Kulesh, N. A.; Svalov, A. V.; Stepanova, E. A.

    2015-06-01

    A systematic investigation of the magnetic properties of amorphous films in ( RE) x Co100 - x binary systems in the ground state with rare-earth elements ( RE) of different types has been performed. The concentration dependences of the average atomic magnetic moments of cobalt ( m Co), gadolinium ( m Gd), and terbium ( m Tb) have been determined from the analysis of the spontaneous magnetization of the films with a nonmagnetic rare-earth element (La), a rare-earth element with a spherical electron shell (Gd), and a rareearth element with a large orbital magnetic moment (Tb). It has been shown that, in the range 0 < x < 50 at %, the magnetic moment m Co decreases from 1.7 μB to zero, the magnetic moment m Gd remains unchanged and almost coincides with the magnetic moment of the free atom (7 μB), and the value of m Tb decreases monotonically, but the rate of decrease depends on the method of the sample preparation. The revealed regularities are associated with the concentration change in the electronic structure of cobalt and with the specificity of the magnetic structure of the films, which has a ferromagnetic, ferrimagnetic, or sperimagnetic character for samples containing La, Gd, or Tb, respectively.

  20. Atmospheric chemistry of isoflurane, desflurane, and sevoflurane: kinetics and mechanisms of reactions with chlorine atoms and OH radicals and global warming potentials.

    PubMed

    Sulbaek Andersen, Mads P; Nielsen, Ole J; Karpichev, Boris; Wallington, Timothy J; Sander, Stanley P

    2012-06-21

    The smog chamber/Fourier-transform infrared spectroscopy (FTIR) technique was used to measure the rate coefficients k(Cl + CF(3)CHClOCHF(2), isoflurane) = (4.5 ± 0.8) × 10(-15), k(Cl + CF(3)CHFOCHF(2), desflurane) = (1.0 ± 0.3) × 10(-15), k(Cl + (CF(3))(2)CHOCH(2)F, sevoflurane) = (1.1 ± 0.1) × 10(-13), and k(OH + (CF(3))(2)CHOCH(2)F) = (3.5 ± 0.7) × 10(-14) cm(3) molecule(-1) in 700 Torr of N(2)/air diluent at 295 ± 2 K. An upper limit of 6 × 10(-17) cm(3) molecule(-1) was established for k(Cl + (CF(3))(2)CHOC(O)F). The laser photolysis/laser-induced fluorescence (LP/LIF) technique was employed to determine hydroxyl radical rate coefficients as a function of temperature (241-298 K): k(OH + CF(3)CHFOCHF(2)) = (7.05 ± 1.80) × 10(-13) exp[-(1551 ± 72)/T] cm(3) molecule(-1); k(296 ± 1 K) = (3.73 ± 0.08) × 10(-15) cm(3) molecule(-1), and k(OH + (CF(3))(2)CHOCH(2)F) = (9.98 ± 3.24) × 10(-13) exp[-(969 ± 82)/T] cm(3) molecule(-1); k(298 ± 1 K) = (3.94 ± 0.30) × 10(-14) cm(3) molecule(-1). The rate coefficient of k(OH + CF(3)CHClOCHF(2), 296 ± 1 K) = (1.45 ± 0.16) × 10(-14) cm(3) molecule(-1) was also determined. Chlorine atoms react with CF(3)CHFOCHF(2) via H-abstraction to give CF(3)CFOCHF(2) and CF(3)CHFOCF(2) radicals in yields of approximately 83% and 17%. The major atmospheric fate of the CF(3)C(O)FOCHF(2) alkoxy radical is decomposition via elimination of CF(3) to give FC(O)OCHF(2) and is unaffected by the method used to generate the CF(3)C(O)FOCHF(2) radicals. CF(3)CHFOCF(2) radicals add O(2) and are converted by subsequent reactions into CF(3)CHFOCF(2)O alkoxy radicals, which decompose to give COF(2) and CF(3)CHFO radicals. In 700 Torr of air 82% of CF(3)CHFO radicals undergo C-C scission to yield HC(O)F and CF(3) radicals with the remaining 18% reacting with O(2) to give CF(3)C(O)F. Atmospheric oxidation of (CF(3))(2)CHOCH(2)F gives (CF(3))(2)CHOC(O)F in a molar yield of 93 ± 6% with CF(3)C(O)CF(3) and HCOF as minor products. The IR

  1. A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Dolgovskiy, V.; Lebedev, V.; Colombo, S.; Weis, A.; Michen, B.; Ackermann-Hirschi, L.; Petri-Fink, A.

    2015-04-01

    The discrimination of immobilised superparamagnetic iron oxide nanoparticles (SPIONs) against SPIONs in fluid environments via their magnetic relaxation behaviour is a powerful tool for bio-medical imaging. Here we demonstrate that a gradiometer of laser-pumped atomic magnetometers can be used to record accurate time series of the relaxing magnetic field produced by pre-polarised SPIONs. We have investigated dry in vitro maghemite nanoparticle samples with different size distributions (average radii ranging from 14 to 21 nm) and analysed their relaxation using the Néel-Brown formalism. Fitting our model function to the magnetorelaxation (MRX) data allows us to extract the anisotropy constant K and the saturation magnetisation MS of each sample. While the latter was found not to depend on the particle size, we observe that K is inversely proportional to the (time- and size-) averaged volume of the magnetised particle fraction. We have identified the range of SPION sizes that are best suited for MRX detection considering our specific experimental conditions and sample preparation technique.

  2. Nuclear magnetic resonance parameters of atomic xenon dissolved in Gay-Berne model liquid crystal.

    PubMed

    Lintuvuori, Juho; Straka, Michal; Vaara, Juha

    2007-03-01

    We present constant-pressure Monte Carlo simulations of nuclear magnetic resonance (NMR) spectral parameters, nuclear magnetic shielding relative to the free atom as well as nuclear quadrupole coupling, for atomic xenon dissolved in a model thermotropic liquid crystal. The solvent is described by Gay-Berne (GB) molecules with parametrization kappa=4.4, kappa{'}=20.0 , and mu=nu=1 . The reduced pressure of P{*}=2.0 is used. Previous simulations of a pure GB system with this parametrization have shown that upon lowering the temperature, the model exhibits isotropic, nematic, smectic- A , and smectic- B /molecular crystal phases. We introduce spherical xenon solutes and adjust the energy and length scales of the GB-Xe interaction to those of the GB-GB interaction. This is done through first principles quantum chemical calculations carried out for a dimer of model mesogens as well as the mesogen-xenon complex. We preparametrize quantum chemically the Xe nuclear shielding and quadrupole coupling tensors when interacting with the model mesogen, and use the parametrization in a pairwise additive fashion in the analysis of the simulation. We present the temperature evolution of {129/131}Xe shielding and 131Xe quadrupole coupling in the different phases of the GB model. From the simulations, separate isotropic and anisotropic contributions to the experimentally available total shielding can be obtained. At the experimentally relevant concentration, the presence of the xenon atoms does not significantly affect the phase behavior as compared to the pure GB model. The simulations reproduce many of the characteristic experimental features of Xe NMR in real thermotropic LCs: Discontinuity in the value or trends of the shielding and quadrupole coupling at the nematic-isotropic and smectic-A-nematic phase transitions, nonlinear shift evolution in the nematic phase reflecting the behavior of the orientational order parameter, and decreasing shift in the smectic-A phase. The last

  3. Nuclear magnetic resonance parameters of atomic xenon dissolved in Gay-Berne model liquid crystal

    NASA Astrophysics Data System (ADS)

    Lintuvuori, Juho; Straka, Michal; Vaara, Juha

    2007-03-01

    We present constant-pressure Monte Carlo simulations of nuclear magnetic resonance (NMR) spectral parameters, nuclear magnetic shielding relative to the free atom as well as nuclear quadrupole coupling, for atomic xenon dissolved in a model thermotropic liquid crystal. The solvent is described by Gay-Berne (GB) molecules with parametrization κ=4.4 , κ'=20.0 , and μ=ν=1 . The reduced pressure of P⋆=2.0 is used. Previous simulations of a pure GB system with this parametrization have shown that upon lowering the temperature, the model exhibits isotropic, nematic, smectic- A , and smectic- B /molecular crystal phases. We introduce spherical xenon solutes and adjust the energy and length scales of the GB-Xe interaction to those of the GB-GB interaction. This is done through first principles quantum chemical calculations carried out for a dimer of model mesogens as well as the mesogen-xenon complex. We preparametrize quantum chemically the Xe nuclear shielding and quadrupole coupling tensors when interacting with the model mesogen, and use the parametrization in a pairwise additive fashion in the analysis of the simulation. We present the temperature evolution of Xe129/131 shielding and Xe131 quadrupole coupling in the different phases of the GB model. From the simulations, separate isotropic and anisotropic contributions to the experimentally available total shielding can be obtained. At the experimentally relevant concentration, the presence of the xenon atoms does not significantly affect the phase behavior as compared to the pure GB model. The simulations reproduce many of the characteristic experimental features of Xe NMR in real thermotropic LCs: Discontinuity in the value or trends of the shielding and quadrupole coupling at the nematic-isotropic and smectic- A -nematic phase transitions, nonlinear shift evolution in the nematic phase reflecting the behavior of the orientational order parameter, and decreasing shift in the smectic- A phase. The last

  4. Comment on "Surface electromagnetic wave equations in a warm magnetized quantum plasma" [Phys. Plasmas 21, 072114 (2014)

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2016-07-01

    In a recent article [C. Li et al., Phys. Plasmas 21, 072114 (2014)], Li et al. studied the propagation of surface waves on a magnetized quantum plasma half-space in the Voigt configuration (in this case, the magnetic field is parallel to the surface but is perpendicular to the direction of propagation). Here, we present a fresh look at the problem and obtain a new form of dispersion relation of surface waves of the system. We find that our new dispersion relation does not agree with the result obtained by Li et al.

  5. Investigation at the atomic scale of the Co spatial distribution in Zn(Co)O magnetic semiconductor oxide

    SciTech Connect

    Larde, R.; Talbot, E.; Vurpillot, F.; Pareige, P.; Schmerber, G.; Beaurepaire, E.; Dinia, A.; Pierron-Bohnes, V.

    2009-06-15

    A sputtered Zn{sub 0.95}Co{sub 0.05}O layer was chemically analyzed at the atomic scale in order to provide an accurate image of the distribution of Co atoms in the ZnO matrix. The investigation of the magnetic properties shows that the as-deposited Zn{sub 0.95}Co{sub 0.05}O is ferromagnetic at room temperature. Atom probe tomography reveals a homogeneous distribution of all chemical species in the layer and the absence of any Co clustering. This result proves that the ferromagnetic properties of this magnetic semiconductor cannot be attributed to a secondary phase or to metallic Co precipitates within the layer.

  6. Measurement of a false electric dipole moment signal from 199Hg atoms exposed to an inhomogeneous magnetic field

    NASA Astrophysics Data System (ADS)

    Afach, S.; Baker, C. A.; Ban, G.; Bison, G.; Bodek, K.; Chowdhuri, Z.; Daum, M.; Fertl, M.; Franke, B.; Geltenbort, P.; Green, K.; van der Grinten, M. G. D.; Grujic, Z.; Harris, P. G.; Heil, W.; Hélaine, V.; Henneck, R.; Horras, M.; Iaydjiev, P.; Ivanov, S. N.; Kasprzak, M.; Kermaïdic, Y.; Kirch, K.; Knowles, P.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Lemière, Y.; Mtchedlishvili, A.; Naviliat-Cuncic, O.; Pendlebury, J. M.; Piegsa, F. M.; Pignol, G.; Prashant, P. N.; Quéméner, G.; Rebreyend, D.; Ries, D.; Roccia, S.; Schmidt-Wellenburg, P.; Severijns, N.; Weis, A.; Wursten, E.; Wyszynski, G.; Zejma, J.; Zenner, J.; Zsigmond, G.

    2015-10-01

    We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for 199Hg atoms contained in a volume permeated with aligned magnetic and electric fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.

  7. Electronic and magnetic properties of a carbon atom chemisorbed on model clusters simulating the (100) surface of nickel

    NASA Astrophysics Data System (ADS)

    Fournier, R.; Andzelm, J.; Goursot, A.; Russo, N.; Salahub, D. R.

    1990-08-01

    Both spin-polarized and unpolarized linear combinations of Gaussian-type orbitals-model core potential-local spin density (LCGTO-MCP-LSD) calculations have been performed for clusters representing the three possible high symmetry chemisorption sites for carbon on the (100) surface of nickel. We found that the most stable chemisorption site is the fourfold hollow, in agreement with the experimental evidence. For this site, the computed equilibrium NiC distances are 1.79 and 1.77 Å at the spin-polarized and unpolarized levels, very close to the most recent experimental measurements. The calculated spin-polarized vibrational frequency perpendicular to the surface is found to be 407 cm-1 (410 cm-1 expt). The values of the binding energy are 11.5 and 11.8 eV at polarized and unpolarized levels, respectively (˜7 eV, expt); the carbon atom is strongly bound, essentially by a triple bond formed by interaction of the px, py, and pz orbitals of carbon with, primarily, the d orbitals of the four nearby surface nickel atoms. The effect of carbon chemisorption on the nickel magnetism has also been studied. The addition of the carbon atom reduces the spin magnetic moment of pure nickel by 2 or 4 μB depending on which of the two nearly degenerate nickel cluster states is taken as reference. The reduction of atomic spin magnetic moments is clearly larger on the 4 nickel atoms nearest to the carbon. The global and local (atomic) reduction in spin magnetic moments originate from some up-spin d density of states being pushed above EF, through antibonding interactions with the carbon 2p orbitals, and hence emptied.

  8. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  9. Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

    SciTech Connect

    Williams, Kurtis A.; Winget, D. E.; Montgomery, M. H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.; Dufour, Patrick; Kepler, S. O.; Bolte, Michael; Liebert, James E-mail: jamesliebert@gmail.com

    2013-06-01

    We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T {sub eff} ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

  10. Studies on soliton energy at critical and noncritical densities of negative ions in an inhomogeneous magnetized warm plasma

    SciTech Connect

    Singh, Dhananjay K.; Malik, Hitendra K.

    2007-11-15

    Considering an inhomogeneous plasma having finite-temperature negative and positive ions, and the isothermal electrons in the presence of an external magnetic field, the solitons at noncritical and critical densities of the negative ions are studied through Korteweg-deVries (KdV) and modified Korteweg-deVries (mKdV) equations, respectively. The compressive (rarefactive) KdV solitons are found to propagate when the negative ion concentration is less (greater) than the critical density of the negative ions. At the critical density, both the compressive and the rarefactive solitons of equal amplitudes are found to occur. The energies of the compressive KdV soliton and the mKdV solitons are found to increase and that of the rarefactive KdV soliton is found to decrease with the negative ion density. Soliton energy for both the KdV and the mKdV solitons gets lowered under the effect of stronger magnetic field. The effect of ion temperature is to increase the energy of the compressive KdV soliton, whereas the energy of the rarefactive KdV soliton as well as of the mKdV solitons gets decreased. The variation of the energy with the obliqueness of the magnetic field is different for the KdV and the mKdV solitons.

  11. Ionization of the hydrogen atom in strong magnetic fields. Beyond the adiabatic approximation.

    NASA Astrophysics Data System (ADS)

    Potekhin, A. Y.; Pavlov, G. G.; Ventura, J.

    1997-01-01

    High magnetic fields in neutron stars, B~10^11^-10^13^G, substantially modify the properties of atoms and their interaction with radiation. In particular, the photoionization cross section becomes anisotropic and polarization dependent, being strongly reduced when the radiation is polarized perpendicular to the field. In a number of previous works based on the adiabatic approximation the conclusion was drawn that this transverse cross section vanishes for frequencies ω smaller than the electron cyclotron frequency ω_c_=eB/(m_e_c). In other works (which employed a different form of the interaction operator) appreciable finite values were obtained, ~σ_0gamma^-1^ near the photoionization threshold, where σ_0_ is the cross section without magnetic field, and γ=B/(2.35x10^9^G). Since it is the transverse cross section which determines the properties of radiation emitted from neutron star atmospheres, an adequate interpretation of the neutron star thermal-like radiation requires a resolution of this controversy. In the present work we calculate the atomic wave functions for both discrete and continuum states by solving the coupled channel equations allowing the admixture between different Landau levels, which provides much higher accuracy than the adiabatic approximation. This enables us to resolve the above contradiction in favour of the finite transverse cross sections at ω<ω_c_. Moreover, for any form of the interaction operator the non-adiabatic corrections appear to be substantial for frequencies ω> 0.3ω_c_. The non-adiabatic treatment of the continuum includes coupling between closed and open channels, which leads to the autoionization of quasi-bound energy levels associated with the electron cyclotron (Landau) excitations and gives rise to Beutler-Fano resonances of the photoionization cross section. We calculate the autoionization widths of these quasi-bound levels and compare them with the radiative widths. The correlation of the open channels is

  12. Global Warming?

    ERIC Educational Resources Information Center

    Eichman, Julia Christensen; Brown, Jeff A.

    1994-01-01

    Presents information and data on an experiment designed to test whether different atmosphere compositions are affected by light and temperature during both cooling and heating. Although flawed, the experiment should help students appreciate the difficulties that researchers face when trying to find evidence of global warming. (PR)

  13. Revealing the Atomic Site-Dependent g Factor within a Single Magnetic Molecule via the Extended Kondo Effect

    NASA Astrophysics Data System (ADS)

    Du, Shixuan

    Control over charge and spin states at the single molecule level is crucial not only for a fundamental understanding of charge and spin interactions but also represents a prerequisite for development of molecular electronics and spintronics. In this talk, I will talk about the extended spin distribution in space beyond the central Mn ion, and onto the non-magnetic constituent atoms of the MnPc molecule. This extended spin distribution results in an extended Kondo effect, which can be explained by spin polarization induced by symmetry breaking of the molecular framework, as confirmed by DFT calculations. Measuring the evolution of the Kondo splitting with applied magnetic fields at different atomic sites, we find a spatial variation of the g-factor within a single molecule for the first time. The existence of atomic site-dependent g-factors can be attributed to specific molecular orbitals distributed over the entire molecule. This work not only open up a new opportunity for quantum information recording, but also provide a new route to explore the internal electronic and spin structure of complex molecules, hard to achieve otherwise. (L. W. Liu et al., Phys. Rev. Lett. 2015, 114, 126601. In collaboration with Liwei Liu, Kai Yang, Yuhang Jiang, Li Gao, Qi Liu, Boqun Song, Wende Xiao, Haitao Zhou, Hongjun Gao in CAS, Min Ouyang in MU, and A.H. Castro Neto in SNU.) Revealing the Atomic Site-Dependent g Factor within a Single Magnetic Molecule via the Extended Kondo Effect.

  14. Manipulation of p-wave scattering of cold atoms in low dimensions using the magnetic field vector

    NASA Astrophysics Data System (ADS)

    Peng, Shi-Guo; Tan, Shina; Jiang, Kaijun

    2014-03-01

    It is well known that the magnetic Feshbach resonances of cold atoms are sensitive to the magnitude of the external magnetic field. Much less attention has been paid to the direction of such a field. In this work we calculate the scattering properties of spin polarized fermionic atoms in reduced dimensions, near a p-wave Feshbach resonance. Because of spatial anisotropy of the p-wave interaction, the scattering has nontrivial dependence on both the magnitude and the direction of the magnetic field. In addition, we identify an inelastic scattering process which is impossible in the isotropic-interaction model; the rate of this process depends considerably on the direction of the magnetic field. Significantly, an EPR entangled pair of identical fermions may be produced during this inelastic collision. This work opens a new method to manipulate resonant cold atomic interactions. CPSF (Grant No. 2012M510187), Special Financial Grant from CPSF (Grant No. 2013T60762), the NSFC projects (Grant No. 11004224 and No.11204355) and the NFRP- China (Grant No. 2011CB921601), NSF (Grant No. PHY-1068511), Alfred P. Sloan Foundation

  15. Roles of Atomic Injection Rate and External Magnetic Field on Optical Properties of Elliptical Polarized Probe Light

    NASA Astrophysics Data System (ADS)

    Karimi, R.; Asadpour, S. H.; Batebi, S.; Rahimpour Soleimani, H.

    2016-01-01

    In this paper we investigate the optical properties of an open four-level tripod atomic system driven by an elliptically polarized probe field in the presence of the external magnetic field and compare its properties with the corresponding closed system. Our result reveals that absorption, dispersion and group velocity of probe field can be manipulated by adjusting the phase difference between the two circularly polarized components of a single coherent field, magnetic field and cavity parameters i.e. the atomic exit rate from cavity and atomic injection rates. We show that the system can exhibit multiple electromagnetically induced transparency windows in the presence of the external magnetic field. The numerical result shows that the probe field in the open system can be amplified by appropriate choice of cavity parameters, while in the closed system with introduce appropriate phase difference between fields the probe field can be enhanced. Also it is shown that the group velocity of light pulse can be controlled by external magnetic field, relative phase of applied fields and cavity parameters. By changing the parameters the group velocity of light pulse changes from subluminal to superluminal light propagation and vice versa.

  16. Highly tunable magnetism in silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain

    SciTech Connect

    Zheng, Rui; Ni, Jun; Chen, Ying

    2015-12-28

    We have investigated the magnetic properties of silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain by the first-principles calculations. We find that Cr and Fe doped silicenes show strain-tunable magnetism. (1) The magnetism of Cr and Fe doped silicenes exhibits sharp transitions from low spin states to high spin states by a small isotropic tensile strain. Specially for Fe doped silicene, a nearly nonmagnetic state changes to a high magnetic state by a small isotropic tensile strain. (2) The magnetic moments of Fe doped silicene also show a sharp jump to ∼2 μ{sub B} at a small threshold of the uniaxial strain, and the magnetic moments of Cr doped silicene increase gradually to ∼4 μ{sub B} with the increase of uniaxial strain. (3) The electronic and magnetic properties of Cr and Fe doped silicenes are sensitive to the magnitude and direction of the external strain. The highly tunable magnetism may be applied in the spintronic devices.

  17. Magnetic properties of Mg12O12 nanocage doped with transition metal atoms (Mn, Fe, Co and Ni): DFT study

    NASA Astrophysics Data System (ADS)

    Javan, Masoud Bezi

    2015-07-01

    Binding energy of the Mg12O12 nanocage doped with transition metals (TM=Mn, Fe, Co and Ni) in endohedrally, exohedrally and substitutionally forms were studied using density functional theory with the generalized gradient approximation exchange-correlation functional along 6 different paths inside and outside of the Mg12O12 nanocage. The most stable structures were determined with full geometry optimization near the minimum of the binding energy curves of all the examined paths inside and outside of the Mg12O12 nanocage. The results reveal that for all stable structures, the Ni atom has a larger binding energy than the other TM atoms. It is also found that for all complexes additional peaks contributed by TM-3d, 4s and 4p states appear in the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gap of the host MgO cluster. The mid-gap states are mainly due to the hybridization between TM-3d, 4s and 4p orbitals and the cage π orbitals. The magnetic moment of the endohedrally doped TM atoms in the Mg12O12 are preserved to some extent due to the interaction between the TM and Mg12O12 nanocage, in contrast to the completely quenched magnetic moment of the Fe and Ni atoms in the Mg11(TM)O12 complexes. Furthermore, charge population analysis shows that charge transfer occurs from TM atom to the cage for endohedrally and substitutionally doping.

  18. Electronic and magnetic behaviors of graphene with 5d series transition metal atom substitutions: A first-principles study

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Tang, Wencheng; Ren, Qingqiang; Zhao, Yiming; Wang, Sake; Yu, Jin; Du, Yanhui; Hao, Yitong

    2016-06-01

    The electronic structures and magnetic behaviors of graphene with 5d series transition metal atom substitutions are investigated by performing first-principles calculations. All the impurities are tightly bonded to single vacancy in a graphene sheet. The substitutions of La and Ta lead to Fermi level shifting to valence and conduction band, respectively. Both the two substitutions result in metallic properties. Moreover, the Hf, Os and Pt-substituted systems exhibit semiconductor properties, while the Re and Ir-substituted ones exhibit robust half-metallic properties. Interestingly, W-substituted system shows dilute magnetic semiconductor property. On the other hand, the substitution of Ta, W, Re and Ir induce 0.86 μB, 2 μB, 1 μB and 0.99 μB magnetic moment, respectively. Our studies demonstrate that the 5d series transition metal substituted graphene have potential applications in nanoelectronics, spintronics and magnetic storage devices.

  19. Atomic layer deposition of cobalt carbide films and their magnetic properties using propanol as a reducing agent

    NASA Astrophysics Data System (ADS)

    Sarr, Mouhamadou; Bahlawane, Naoufal; Arl, Didier; Dossot, Manuel; McRae, Edward; Lenoble, Damien

    2016-08-01

    The investigation of highly conformal thin films using Atomic Layer Deposition (ALD) is driven by a variety of applications in modern technologies. In particular, the emergence of 3D memory device architectures requires conformal materials with tuneable magnetic properties. Here, nanocomposites of carbon, cobalt and cobalt carbide are deposited by ALD using cobalt acetylacetonate with propanol as a reducing agent. Films were grown by varying the ALD deposition parameters including deposition temperature and propanol exposure time. The morphology, the chemical composition and the crystalline structure of the cobalt carbide film were investigated. Vibrating Sample Magnetometer (VSM) measurements revealed magnetic hysteresis loops with a coercivity reaching 500 Oe and a maximal saturation magnetization of 0.9 T with a grain size less than 15 nm. Magnetic properties are shown to be tuneable by adjusting the deposition parameters that significantly affect the microstructure and the composition of the deposited films.

  20. Global warming

    NASA Astrophysics Data System (ADS)

    Houghton, John

    2005-06-01

    'Global warming' is a phrase that refers to the effect on the climate of human activities, in particular the burning of fossil fuels (coal, oil and gas) and large-scale deforestation, which cause emissions to the atmosphere of large amounts of 'greenhouse gases', of which the most important is carbon dioxide. Such gases absorb infrared radiation emitted by the Earth's surface and act as blankets over the surface keeping it warmer than it would otherwise be. Associated with this warming are changes of climate. The basic science of the 'greenhouse effect' that leads to the warming is well understood. More detailed understanding relies on numerical models of the climate that integrate the basic dynamical and physical equations describing the complete climate system. Many of the likely characteristics of the resulting changes in climate (such as more frequent heat waves, increases in rainfall, increase in frequency and intensity of many extreme climate events) can be identified. Substantial uncertainties remain in knowledge of some of the feedbacks within the climate system (that affect the overall magnitude of change) and in much of the detail of likely regional change. Because of its negative impacts on human communities (including for instance substantial sea-level rise) and on ecosystems, global warming is the most important environmental problem the world faces. Adaptation to the inevitable impacts and mitigation to reduce their magnitude are both necessary. International action is being taken by the world's scientific and political communities. Because of the need for urgent action, the greatest challenge is to move rapidly to much increased energy efficiency and to non-fossil-fuel energy sources.

  1. Low frequency magnetic field suppression in an atomic spin co-magnetometer with a large electron magnetic field

    NASA Astrophysics Data System (ADS)

    Fang, Jiancheng; Chen, Yao; Zou, Sheng; Liu, Xuejing; Hu, Zhaohui; Quan, Wei; Yuan, Heng; Ding, Ming

    2016-03-01

    In a K-Rb-21Ne co-magnetometer, the Rb electron magnetic field which is experienced by the nuclear spin is about 100 times larger than that of the K in a K-3He co-magnetometer. The large electron magnetic field which is neglected in the K-3He co-magnetometer coupled Bloch equations model is considered here in the K-Rb-21Ne co-magnetometer to study the low frequency magnetic field suppression effect. Theoretical analysis and experimental results shows that in the K-Rb-21Ne spin co-magnetometer, not only the nuclear spin but also the large electron spin magnetic field compensate the external magnetic field noise. By comparison, only the 3He nuclear spins mainly compensate the external magnetic field noise in a K-3He co-magnetometer. With this study, in addition to just increasing the magnetic field of the nuclear spins, we can suppress the magnetic field noise by increasing the density of the electron spin. We also studied how the magnetic field suppression effect relates to the scale factor of the K-Rb-21Ne co-magnetometer and we compared the scale factor with that of the K-3He co-magnetometer. Lastly, we show the sensitivity of our co-magnetometer. The magnetic field noise, the air density fluctuation noise and pumping power optimization are studied to improve the sensitivity of the co-magnetometer.

  2. Circuit-quantum electrodynamics with direct magnetic coupling to single-atom spin qubits in isotopically enriched {sup 28}Si

    SciTech Connect

    Tosi, Guilherme Mohiyaddin, Fahd A.; Morello, Andrea; Huebl, Hans

    2014-08-15

    Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified {sup 28}Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.

  3. Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields.

    PubMed

    Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

    2016-05-01

    This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics. PMID:27300989

  4. Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

    2016-05-01

    This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.

  5. Relativistic and electron-correlation effects on the nuclear magnetic resonance shieldings of molecules containing tin and lead atoms.

    PubMed

    Maldonado, Alejandro F; Aucar, Gustavo A

    2014-09-11

    The reference values for NMR magnetic shieldings, σ(ref), are of the highest importance when theoretical analysis of chemical shifts are envisaged. The fact that the nonrelativistically valid relationship among spin-rotation constants and magnetic shieldings is not any longer valid for heavy atoms requires that the search for σ(ref) for such atoms needs new strategies to follow. We present here results of σ(ref) that were obtained by applying our own simple procedure which mixes accurate experimental chemical shifts (δ) and theoretical magnetic shieldings (σ). We calculated σ(Sn) and σ(Pb) in a family of heavy-halogen-containing molecules. We found out that σ(ref)[Sn;Sn(CH3)4] in gas phase should be close to 3864.11 ± 20.05 ppm (0.5%). For Pb atom, σ(ref)[Pb;Pb(CH3)4] should be close to 14475.1 ± 500.7 ppm. Such theoretical values correspond to calculations with the relativistic polarization propagator method, RelPPA, at the RPA level of approach. They are closer to experimental values as compared to those obtained applying few different functionals such as PBE0, B3LYP, BLYP, BP86, KT2, and KT3 of the density functional theory, DFT. We studied tin and lead shieldings of the XY(4-n)Z(n) (X = Sn, Pb; Y, Z = H, F, Cl, Br, I) and PbH(4-n)I(n) (n = 0, 1, 2, 3, 4) family of compounds with four-component functionals as implemented in the DIRAC code. For these systems results of calculations with RelPPA-RPA are more reliable than DFT ones. We argue about why those DFT functionals must be modified in order to obtain more accurate results of NMR magnetic shieldings within the relativistic regime: first, there is a dependence among both electron-correlation and relativistic effects that should be introduced in some way in the functionals; and second, the DIRAC code uses standard nonrelativistic functionals and the functionals B3LYP and PBE0 were parametrized only with data taken from light elements. It can explain why they are not able to properly introduce

  6. Shielding of longitudinal magnetic fields with thin, closely, spaced concentric cylindrical shells with applications to atomic clocks

    NASA Technical Reports Server (NTRS)

    Wolf, S. A.; Gubser, D. U.; Cox, J. E.

    1978-01-01

    A general formula is given for the longitudinal shielding effectiveness of N closed concentric cylinders. The use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental results on three sets of shields fabricated by three manufacturers are presented. Two of the sets were designed employing the techniques described. Agreement between the experimental results and the design calculations is then demonstrated.

  7. A magnetic recoil spectrometer (MRS) for ρR_fuel and Ti measurements of warm, fizzle and ignited implosions at OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Frenje, J. A.; Petrasso, R. D.; Li, C. K.; Séguin, F. H.; Deciantis, J. L.; Kurebayashi, S.; Rygg, J. R.; Glebov, V. Yu.; Meyerhofer, D. D.; Sangster, T. C.; Soures, J. M.; Hatchett, S. P.; Hann, S. W.; Schmid, G. J.; Landen, O. L.; Izumi, N.

    2003-10-01

    A method for determining ρR_fuel of cryogenic deuterium-tritium plasmas involves measurement of the energy spectrum of elastically-scattered, primary neutrons. A spectrometer has been designed for doing this at OMEGA and the NIF, using scattered neutrons in the energy range 7-10 MeV to determine ρR_fuel and primary neutrons to measure T_i. The instrument utilizes a magnet and a conversion foil for production of charged particles. A large dynamic range (>10^6) will allow operation at yields as low as 10^12. This will allow ρR_fuel and Ti measurements of warm and cryogenic DT targets at OMEGA, and fizzle and ignited cryogenic DT targets at the NIF. This work was supported in part by the US DoE (contract W-7405-ENG-48 with LLNL, grant DE-FG03-99DP00300 and Cooperative Agreement DE-FC03-92SF19460), LLE (subcontract P0410025G), and LLNL (subcontract B313975).

  8. Ultracold magnetically tunable interactions without radiative-charge-transfer losses between Ca+, Sr+, Ba+, and Yb+ ions and Cr atoms

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2015-12-01

    The Ca+, Sr+, Ba+, and Yb+ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. Ab initio techniques are applied to investigate electronic-ground-state properties of the (CaCr)+, (SrCr)+, (BaCr)+, and (YbCr)+ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin-restricted open-shell coupled-cluster method restricted to single, double, and noniterative triple excitations and the multireference configuration-interaction method restricted to single and double excitations are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction coefficients are also reported. Finally, magnetic Feshbach resonances between the Ca+, Sr+, Ba+, and Yb+ ions interacting with the Cr atoms are analyzed. The present proposal opens the way towards robust quantum simulations and computations with ultracold ion-atom systems free of radiative charge-transfer losses.

  9. Imaging magnetic scalar potentials by laser-induced fluorescence from bright and dark atoms

    NASA Astrophysics Data System (ADS)

    Fescenko, I.; Weis, A.

    2014-06-01

    We present a spectroscopic method for mapping two-dimensional distributions of magnetic field strengths (magnetic scalar potential lines) using charge-coupled device (CCD) recordings of the fluorescence patterns emitted by spin-polarized Cs vapour in a buffer gas exposed to inhomogeneous magnetic fields. The method relies on the position-selective destruction of spin polarization by magnetic resonances induced by multi-component oscillating magnetic fields, such that magnetic potential lines can be directly detected by the CCD camera. We also present a generic algebraic model allowing for the calculation of the fluorescence patterns and find excellent agreement with the experimental observations for three distinct inhomogeneous field topologies. The spatial resolution obtained with these proof-of-principle experiments is of the order of 1 mm. A substantial increase of spatial and magnetic field resolution is expected by deploying the method in a magnetically shielded environment.

  10. Optimizing the flux coupling between a nanoSQUID and a magnetic particle using atomic force microscope nanolithography

    NASA Astrophysics Data System (ADS)

    Faucher, M.; Jubert, P. O.; Fruchart, O.; Wernsdorfer, W.; Bouchiat, V.

    2009-06-01

    We present results of niobium based SQUID magnetometers for which the weak links are engineered by the local oxidation of thin films using an atomic force microscope (AFM). Firstly, we show that this technique allows the creation of variable thickness bridges with 10 nm lateral resolution. Precise control of the weak link milling is offered by the possibility to monitor, in real-time, the weak link conductance. Such a process is shown to enhance the magnetic field modulation and hence the sensitivity of the magnetometer. Secondly, AFM lithography is used to provide a precise alignment of nanoSQUID weak links with respect to a ferromagnetic iron dot. The magnetization switching of the near-field coupled particle is studied as a function of the applied magnetic field direction.

  11. Atomization characteristics and direct determination of manganese and magnesium in biological samples using a magnetically altered thin-film plasma

    SciTech Connect

    Brewer, S.W. Jr.; Sacks, R.D.

    1988-09-01

    A magnetic field with peak value of 3.7 kG is used to improve the atomization characteristics of an electrically vaporized thin-film plasma for the direct determination of Mg and Mn in solid biological materials. Plasmas are generated by high-current capacitive discharges through 350-..mu..g Ag or Au thin films formed on polypropylene substrates. Radiation intensity vs time plots are compared with and without the magnetic field for the NBS materials bovine liver, oyster tissue, orchard leaves, citrus leaves, tomato leaves, and pine needles. Analytical standard for Mg are prepared from suspensions of MgO powder, and standards for Mn are prepared from aqueous solutions of Mn(NO/sub 3/)/sub 2/ or MnSO/sub 4/. Analytical accuracy usually is improved with the presence of the magnetic field.

  12. Tuning electronic and magnetic properties of blue phosphorene by doping Al, Si, As and Sb atom: A DFT calculation

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Hao, Yitong; Ren, Qingqiang; Zhao, Yiming; Du, Yanhui; Tang, Wencheng

    2016-09-01

    Using density functional theory computations, we systematically investigated the structural, electronic and magnetic properties of Al, Si, As and Sb doped blue phosphorene. The electronic properties of blue phosphorene can be effectively turned by substitutional doping. Especially, Al and Sb lead to an indirect-to-direct-gap transition. The interaction between the impurity and P atoms should be responsible for the transition. In addition, blue phosphorene can exhibit dilute magnetic semiconductor property with doping of Si impurity. The magnetic moment in Si-substituted blue phosphorene predominantly originates from the hybridization of Si-s pz and P-pz orbitals. These results provide many useful applications of blue phosphorene in electronics, optoelectronics and spintronics.

  13. Reversible switching of magnetic states by electric fields in nitrogenized-divacancies graphene decorated by tungsten atoms.

    PubMed

    Ge, Gui-Xian; Sun, Hai-Bin; Sun, Hai-Bing; Han, Yan; Song, Feng-Qi; Zhao, Ji-Jun; Wang, Guang-Hou; Wan, Jian-Guo

    2014-01-01

    Magnetic graphene-based materials have shown great potential for developing high-performance electronic devices at sub-nanometer such as spintronic data storage units. However, a significant reduction of power consumption and great improvement of structural stability are needed before they can be used for actual applications. Based on the first-principles calculations, here we demonstrate that the interaction between tungsten atoms and nitrogenized-divacancies (NDVs) in the hybrid W@NDV-graphene can lead to high stability and large magnetic anisotropy energy (MAE). More importantly, reversible switching between different magnetic states can be implemented by tuning the MAE under different electric fields, and very low energy is consumed during the switching. Such controllable switching of magnetic states is ascribed to the competition between the tensile stain and orbital magnetic anisotropy, which originates from the change in the occupation number of W-5d orbitals under the electric fields. Our results provide a promising avenue for developing high-density magnetic storage units or multi-state logical switching devices with ultralow power at sub-nanometer. PMID:25524662

  14. Reversible switching of magnetic states by electric fields in nitrogenized-divacancies graphene decorated by tungsten atoms

    PubMed Central

    Ge, Gui-Xian; Sun, Hai-Bing; Han, Yan; Song, Feng-Qi; Zhao, Ji-Jun; Wang, Guang-Hou; Wan, Jian-Guo

    2014-01-01

    Magnetic graphene-based materials have shown great potential for developing high-performance electronic devices at sub-nanometer such as spintronic data storage units. However, a significant reduction of power consumption and great improvement of structural stability are needed before they can be used for actual applications. Based on the first-principles calculations, here we demonstrate that the interaction between tungsten atoms and nitrogenized-divacancies (NDVs) in the hybrid W@NDV-graphene can lead to high stability and large magnetic anisotropy energy (MAE). More importantly, reversible switching between different magnetic states can be implemented by tuning the MAE under different electric fields, and very low energy is consumed during the switching. Such controllable switching of magnetic states is ascribed to the competition between the tensile stain and orbital magnetic anisotropy, which originates from the change in the occupation number of W-5d orbitals under the electric fields. Our results provide a promising avenue for developing high-density magnetic storage units or multi-state logical switching devices with ultralow power at sub-nanometer. PMID:25524662

  15. A Simple Demonstration of Atomic and Molecular Orbitals Using Circular Magnets

    ERIC Educational Resources Information Center

    Chakraborty, Maharudra; Mukhopadhyay, Subrata; Das, Ranendu Sekhar

    2014-01-01

    A quite simple and inexpensive technique is described here to represent the approximate shapes of atomic orbitals and the molecular orbitals formed by them following the principles of the linear combination of atomic orbitals (LCAO) method. Molecular orbitals of a few simple molecules can also be pictorially represented. Instructors can employ the…

  16. Probing quantum confinement at the atomic scale with optically detected nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Kempf, James G.

    2001-09-01

    Near-band-gap circularly polarized excitation in III-V semiconductors provides spin-polarized electrons that transfer spin order to lattice nuclei via fluctuations in the contact hyperfine interaction. This process of optical nuclear polarization and the complementary technique of optical detection of nuclear magnetic resonance (NMR) provide extreme sensitivity enhancement and spatial selectivity in structured samples, enabling collection of NMR spectra from samples such as single quantum wells or dots containing as few as ˜105 nuclei. Combining these advances with novel techniques for high spectral resolution, we have probed quantum-confined electronic states near the interface of a single epitaxially grown Al1-x As/GaAs (x = 0.36) heterojunction. Using a novel strategy that we refer to as POWER (p&barbelow;erturbations o&barbelow;bserved w&barbelow;ith e&barbelow;nhanced ṟesolution) NMR, multiple-pulse time suspension is synchronized with bandgap optical irradiation to reveal spectra of effective spin Hamiltonians that are differences between those of the occupied and unoccupied photoexcited electronic state. The underlying NMR linewidth is reduced by three orders of magnitude in these experiments, enabling resolution of an asymmetric line shape due to light-induced hyperfine interactions. The results are successfully fit with the coherent nuclear spin evolution and relaxation theoretically expected for sites distributed over the volume of an electronic excitation weakly localized at a point defect. This analysis establishes a one-to-one relationship, which can be used to follow nuclear spin diffusion, between optical Knight shift and the radial position of lattice nuclei. We have also introduced POWER NMR techniques to characterize the change in electric field associated with cycling from light-on to light-off states via a linear quadrupole Stark effect (LQSE) of the nuclear spins. Simulations of these NMR spectra in terms of the radial electric fields of

  17. Effects of the interplay between atomic and magnetic order on the properties of metamagnetic Ni-Co-Mn-Ga shape memory alloys

    SciTech Connect

    Seguí, C.

    2014-03-21

    Ni-Co-Mn-Ga ferromagnetic shape memory alloys show metamagnetic behavior for a range of Co contents. The temperatures of the structural and magnetic transitions depend strongly on composition and atomic order degree, in such a way that combined composition and thermal treatment allows obtaining martensitic transformation between any magnetic state of austenite and martensite. This work presents a detailed analysis of the effect of atomic order on Ni-Co-Mn-Ga alloys through the evolution of structural and magnetic transitions after quench from high temperatures and during post-quest ageing. It is found that the way in which the atomic order affects the martensitic transformation temperatures and entropy depends on the magnetic order of austenite and martensite. The results can be explained assuming that improvement of atomic order decreases the free energy of the structural phases according to their magnetic order. However, it is assumed in this work that changes in the slope—that is, the entropy—of the Gibbs free energy curves are also decisive to the stability of the two-phase system. The experimental transformation entropy values have been compared with a phenomenological model, based on a Bragg–Williams approximation, accounting for the magnetic contribution. The excellent agreement obtained corroborates the magnetic origin of changes in transformation entropy brought about by atomic ordering.

  18. Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

    SciTech Connect

    Haendel, S.; Marchant, A. L.; Wiles, T. P.; Hopkins, S. A.; Cornish, S. L.

    2012-01-15

    We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of {sup 85}Rb and {sup 87}Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum. To maintain excellent optical access to the region surrounding the surface, magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally, we demonstrate the loading of a hybrid optical-magnetic trap with {sup 87}Rb and the creation of Bose-Einstein condensates via forced evaporative cooling close to the dielectric surface.

  19. Quantum warming

    NASA Astrophysics Data System (ADS)

    2009-01-01

    The demonstration in this issue that strong magnetic confinement of electrons can dramatically increase the operating temperature of terahertz quantum cascade lasers is good news for the dream of reaching room temperature. Nature Photonics spoke with Qing Hu about the result and the future prospects.

  20. Effects of Boron Addition to the Atomic Structure and Soft Magnetic Properties of FeCoB Films

    SciTech Connect

    Yang,A.; Imrane, H.; Lou, J.; Kirkland, J.; Vittoria, C.; Sun, N.; Harris, V.

    2008-01-01

    The magnetic, microwave, and the atomic structure properties of (Fe0.7Co0.3)1?xBx sputtered films on glass substrates were investigated. The addition of boron induced a decrease in coercivity and ferromagnetic resonance linewidth. The amorphous structure was formed at x ? 0.075. Extended x-ray absorption fine structure (EXAFS) of Fe and Co showed the reduced Fourier transform (FT) amplitude, and increased Debye-Waller factors as x was increased, indicating the increased disorder due to the thermal and structural displacements. Possible Fe-B bonding was observed with a reduced bond length, which indicates boron atoms' preference for staying in the interstitial sites in bcc unit cell.

  1. Effects of boron addition to the atomic structure and soft magnetic properties of FeCoB films

    NASA Astrophysics Data System (ADS)

    Yang, Aria; Imrane, Hassan; Lou, Jing; Kirkland, Johnny; Vittoria, Carmine; Sun, Nian; Harris, Vincent G.

    2008-04-01

    The magnetic, microwave, and the atomic structure properties of (Fe0.7Co0.3)1-xBx sputtered films on glass substrates were investigated. The addition of boron induced a decrease in coercivity and ferromagnetic resonance linewidth. The amorphous structure was formed at x ˜0.075. Extended x-ray absorption fine structure (EXAFS) of Fe and Co showed the reduced Fourier transform (FT) amplitude, and increased Debye-Waller factors as x was increased, indicating the increased disorder due to the thermal and structural displacements. Possible Fe-B bonding was observed with a reduced bond length, which indicates boron atoms' preference for staying in the interstitial sites in bcc unit cell.

  2. High Z effects in accounting for radiative component of the electron magnetic moment in hydrogen-like atoms

    NASA Astrophysics Data System (ADS)

    Sveshnikov, K. A.; Khomovskii, D. I.

    2013-03-01

    The behavior of electron energy levels in hydrogen-like atoms is studied while taking into account the nonperturbative interaction between the radiative component of the magnetic moment of a free electron Δ g free and the Coulomb field of an atomic nucleus with charge Z, including those with Z > 137. It is shown that for Zα ≪ 1 the energy-level shift is rather effectively determined through the matrix elements of the corresponding Dirac-Pauli operator with relativistic Coulomb wave functions. At the same time, for superheavy nuclei with Z ˜ 170, this shift, generated by Δ g free, is genuinely nonperturbative, behaves like ˜ Z 5 near the threshold of negative continuum, exceeds all the estimates of radiative corrections coming from vacuum polarization and electron self-energy known so far, and turns out to be at least of the same order as the effects of nuclear charge screening by filled electron shells.

  3. Atom Skimmers and Atom Lasers Utilizing Them

    NASA Technical Reports Server (NTRS)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  4. Magnetic states of Co-, Fe- and Mn-atoms in some Heusler alloys

    NASA Astrophysics Data System (ADS)

    Kido, M.; Ido, H.; Kido, G.

    1992-02-01

    Magnetic and thermal measurements have been made for the Heusler-type alloys Co 2TiSn and Co 2TiAl. The magnetic behaviour of Co 2TiSn was found to be of a typical localized character, and the Co moment has been estimated from the saturation magnetization to be 0.99μ B(=μ f), which agrees well with the Co moment of 1.0μ B(=μ p) estimated by applying the Curie-Weiss law to the observed susceptibility (χ) vs temperature ( T) curve above TC. The magnetic behaviour of Co 2TiAl is similar to that of Co 2TiSn, however, μ p = 0.44μ B is a little larger than μ f = 0.37μ B. The difference between the magnetic properties of the above two alloys is discussed.

  5. Magnetic-field effects in transitions of X Li molecules (X: even isotopes of group II atoms)

    SciTech Connect

    Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

    2011-10-15

    We analyze the Zeeman shift in the (v,N)=(0,0){yields}(1,0) transition frequency of X Li molecules (X: even isotopes of group II atoms), which is of interest in metrology. The Zeeman shift in the transition frequency between stretching states is found to be less than 1 mHz with a magnetic field of 1 G. X {sup 6}Li molecules are more advantageous than X {sup 7}Li molecules for measuring the transition frequency without the Zeeman shift because of the smaller g factor of the Li nuclear spin.

  6. Electric field control of the magnetic anisotropy energy of double-vacancy graphene decorated by iridium atoms.

    PubMed

    Ge, Gui-Xian; Li, Ying-Bin; Wang, Guang-Hou; Wan, Jian-Guo

    2016-04-20

    To solve the fundamental dilemma in data storage applications, it is crucial to manipulate the magnetic anisotropy energy (MAE). Herein, using first-principles calculations, we predict that the system of double-vacancy graphene decorated by iridium atoms possesses high stability, giant MAE, perpendicular-anisotropy and long-range ferromagnetic coupling. More importantly, the amplitude of MAE can be manipulated by electric fields. This is due to the change in the occupation number of Ir-5d orbitals. The present hybrid system could be a high-performance nanoscale information storage device with ultralow energy consumption. PMID:27063394

  7. EIT resonance features in strong magnetic fields in rubidium atomic columns with length varying by 4 orders

    NASA Astrophysics Data System (ADS)

    Mirzoyan, R.; Sargsyan, A.; Sarkisyan, D.; Wojciechowski, A.; Stabrawa, A.; Gawlik, W.

    2016-06-01

    Electromagnetically induced transparency (EIT) resonances are investigated with the 85Rb D 1 line (795 nm) in strong magnetic fields (up to 2 kG) with three different types of spectroscopic vapor cells: the nano-cell with a thickness along the direction of laser light L ≈ 795 nm, the micro-cell with L = 30 μm with the addition of a neon buffer gas, and the centimeter-long glass cell. These cells allowed us to observe systematic changes of the EIT spectra when the increasing magnetic field systematically decoupled the total atomic electron and nuclear angular moments (the Paschen-Back/Back-Goudsmit effects). The observations agree well with a theoretical model. The advantages and disadvantages of a particular type of cell are discussed along with the possible practical applications.

  8. Development of atomic force microscope with wide-band magnetic excitation for study of soft matter dynamics.

    PubMed

    Kageshima, Masami; Chikamoto, Takuma; Ogawa, Tatsuya; Hirata, Yoshiki; Inoue, Takahito; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2009-02-01

    In order to probe dynamical properties of mesoscopic soft matter systems such as polymers, structured liquid, etc., a new atomic force microscopy apparatus with a wide-band magnetic cantilever excitation system was developed. Constant-current driving of an electromagnet up to 1 MHz was implemented with a closed-loop driver circuit. Transfer function of a commercial cantilever attached with a magnetic particle was measured in a frequency range of 1-1000 kHz in distilled water. Effects of the laser spot position, distribution of the force exerted on the cantilever, and difference in the detection scheme on the obtained transfer function are discussed in comparison with theoretical predictions by other research groups. A preliminary result of viscoelasticity spectrum measurement of a single dextran chain is shown and is compared with a recent theoretical calculation. PMID:19256651

  9. Temperature and bias-voltage dependence of atomic-layer-deposited HfO{sub 2}-based magnetic tunnel junctions

    SciTech Connect

    Fabretti, Savio; Zierold, Robert; Nielsch, Kornelius; Voigt, Carmen; Ronning, Carsten; Peretzki, Patrick; Seibt, Michael; Thomas, Andy

    2014-09-29

    Magnetic tunnel junctions with HfO{sub 2} tunnel barriers were prepared through a combination of magnetron sputtering and atomic layer deposition. We investigated the tunneling transport behavior, including the tunnel magnetoresistance ratio and the current-voltage characteristics between room temperature and 2 K. Here, we achieved a tunneling magneto resistance ratio of 10.3% at room temperature and 19.3% at 2 K. Furthermore, we studied the bias-voltage and temperature dependencies and compared the results with those of commonly used alumina- and magnesia-based magnetic tunnel junctions. We observed a polycrystalline/amorphous electrode-barrier system via high-resolution transmission electron microscopy.

  10. Interaction of magnetism with atomic lattice geometry and nanoscale geometric frustration

    NASA Astrophysics Data System (ADS)

    Subramanian, Hemachander

    From lodestones to quantum computers, magnetism has been intricately entwined with scientific and technological development of humankind for millenia. A short chronological list of important experiments, theories and effects connected with magnetism that substantially altered the course of human understanding of the physical world: Magnetites, navigation, the concept of fields, electromagnetism and Maxwell's equations, Zeeman effect, Curie's law, special relativity, quantum mechanical spin, cooperative phenomena, phase transitions, frustration, Ising model, quantum statistical mechanics, magnetic memories, high-temperature superconductivity, spintronics and so on. The seemingly uninteresting effect of magnetic anisotropy is probably the only observable effect that requires for its explanation, both quantum mechanics and special relativity, the two towering theories of twentieth century. This effect arises from the interaction between the spin part and the spatial part of an electron's wavefunction, which is due to the relativistic motion of electron around the nucleus. Without such an interaction, magnetism would have remained as a pure academic interest. The macroscopic manifestation of this spin-orbit interaction, magnetic anisotropy, is the central theme of this thesis. In the first chapter, we explore how ionic displacements in a solid and magnetization directions are tied together through spin-orbit coupling. Magnetic ion doped semiconductor Gallium Manganese Arsenide shows rich and intricate magnetic anisotropies, with one of the anisotropy components unexpected from symmetry grounds. This chapter explains how the inclusion of displacements of the impurity ion helps us explain the apparently unexpected observation of uniaxial magnetic anisotropy in the above material. In the second chapter, we utilize this magnetic anisotropy by bringing together two materials, one with very high and another with negligible anisotropy, to introduce magnetic frustration in a

  11. Magnetocaloric effect of RM2 (R = rare earth, M = Ni, Al) intermetallic compounds made by centrifugal atomization process for magnetic refrigerator

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Asamato, K.; Nishimura, Y.; Zhu, Y.; Abe, S.; Numazawa, T.

    2012-12-01

    RM2 (R = rare earth, M = Al, Ni and Co) compounds have large entropy change and magnetic transition temperatures can be controlled by change of R and/or M so that are suitable to a magnetic refrigerator for hydrogen liquefaction under development. In order to improve refrigerator performance, spherical powdered HoAl2, DyAl2, and GdNi2 compounds with submillimeter diameter were synthesized by centrifugal atomization process. By measuring the magnetization and heat capacity, we obtained entropy change by magnetic fields and entropy as functions of temperature and magnetic field, which are essential for analysing the magnetic refrigeration cycle. All samples showed sharp magnetic transitions and had good potentials for use in magnetic refrigeration.

  12. Nuclear Spin Maser at Highly Stabilized Low Magnetic Field and Search for Atomic EDM

    SciTech Connect

    Yoshimi, A.; Asahi, K.; Inoue, T.; Uchida, M.; Hatakeyama, N.; Tsuchiya, M.; Kagami, S.

    2009-08-04

    A nuclear spin maser is operated at a low static field through an active feedback scheme based on an optical nuclear spin detection and succeeding spin control by a transverse field application. The frequency stability of this optical-coupling spin maser is improved by installation of a low-noise current source for a solenoid magnet producing a static magnetic field in the maser operation. Experimental devices for application of the maser to EDM experiment are being developed.

  13. Atomic-Scale Structure and Local Chemistry of CoFeB-MgO Magnetic Tunnel Junctions.

    PubMed

    Wang, Zhongchang; Saito, Mitsuhiro; McKenna, Keith P; Fukami, Shunsuke; Sato, Hideo; Ikeda, Shoji; Ohno, Hideo; Ikuhara, Yuichi

    2016-03-01

    Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving and chemically identifying each individual stacking layer remains challenging due to spatially localized features that complicate characterizations limiting understanding of the physics of MTJs. Here, we combine advanced electron microscopy, spectroscopy, and first-principles calculations to obtain a direct structural and chemical imaging of the atomically confined layers in a CoFeB-MgO MTJ, and clarify atom diffusion and interface structures in the MTJ following annealing. The combined techniques demonstrate that B diffuses out of CoFeB electrodes into Ta interstitial sites rather than MgO after annealing, and CoFe bonds atomically to MgO grains with an epitaxial orientation relationship by forming Fe(Co)-O bonds, yet without incorporation of CoFe in MgO. These findings afford a comprehensive perspective on structure and chemistry of MTJs, helping to develop high-performance spintronic devices by atomistic design. PMID:26905782

  14. Manipulating Majorana zero modes on atomic rings with an external magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Jian; Neupert, Titus; Bernevig, B. Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles--the Majorana bound states--can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field.

  15. Manipulating Majorana zero modes on atomic rings with an external magnetic field.

    PubMed

    Li, Jian; Neupert, Titus; Bernevig, B Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles--the Majorana bound states--can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field. PMID:26791080

  16. AN ESTIMATE OF THE NEARBY INTERSTELLAR MAGNETIC FIELD USING NEUTRAL ATOMS

    SciTech Connect

    Heerikhuisen, J.; Pogorelov, N. V.

    2011-09-01

    The strength and orientation of the magnetic field in the nearby interstellar medium have remained elusive, despite continual improvements in observations and models. Data from NASA's Voyager mission and the Solar Wind ANisotropies (SWAN) experiment on board Solar and Heliospheric Observatory (SOHO) have placed observational constraints on the magnetic field, and the more recent Interstellar Boundary Explorer (IBEX) data appear to also bear an imprint of the interstellar magnetic field (ISMF). In this paper, we combine computational models of the heliosphere with data from Voyager, SOHO/SWAN, and IBEX to estimate both the strength and direction of the nearby ISMF. On the basis of our simulations, we find that a field strength of 2-3 {mu}G pointing from ecliptic coordinates (220-224, 39-44), combined with an interstellar hydrogen density of {approx}0.15 cm{sup -3}, produces results most consistent with observations.

  17. Electronic and magnetic properties of graphene absorbed with S atom: A first-principles study

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Xiao, H. Y.; Lv, H. F.

    2009-05-15

    Stable configuration, electronic structures, and magnetic behaviors for S adsorption on graphene have been investigated by first-principles calculations. It is found that the adsorption site of S on graphene is coverage dependent. As the increase of coverage from 0 to 0.5 ML, the preferred site is changed from bridge to hollow site. For the adsorption of S at bridge site, no magnetic moment is detected, and the adsorption is characterized by strong hybridization between the S 2s state and graphene σ states. For the adsorption of S at hollow site, a magnetic moment of 1.98 μB was induced. In this case, the hybridization occurs between S 2p states and graphene π states. Furthermore, from the investigation of the surface potential energy curve, we find that graphene is a suitable candidate for the S storage.

  18. Manipulating Majorana zero modes on atomic rings with an external magnetic field

    PubMed Central

    Li, Jian; Neupert, Titus; Bernevig, B. Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles—the Majorana bound states—can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field. PMID:26791080

  19. Atomic scale understanding of magnetic properties in Ni50Fe35Co15

    NASA Astrophysics Data System (ADS)

    Herojit Singh, L.; Govindaraj, R.; Ravishankar, C.; Rajagopalan, S.; Amarendra, G.

    2016-02-01

    Mössbauer spectroscopic studies have been carried out at different temperatures across ferromagnetic to paramagnetic transition in Ni50Fe35Co15 and the evolution of hyperfine parameters such as centre shift and magnetic hyperfine fields with temperature has been studied. Mössbauer spectrum obtained at 300 K in Ni50Fe35Co15 exhibiting fcc crystal structure is a six line pattern with the mean value of the hyperfine field close to 33 Tesla. Ferromagnetic to paramagnetic transition has been observed to occur in this system around 895 K matching with that of magnetization results. Debye temperature of this nickel rich alloy is deduced to be around 470 K matching with that of Ni. Effect of prolonged annealing at 750 K on the magnetic property is also investigated with respect to the thermal stability of the alloy .

  20. Atomic scale visualization of novel magnetic phase transitions in Fe-based superconductor Sr4V2O6Fe2As2

    NASA Astrophysics Data System (ADS)

    Choi, Seokhwan; Jang, Won-Jun; Ok, Jong Mok; Choi, Hyun Woo; Lee, Hyun Jung; Jung, Jin Oh; Son, Dong Hyun; Suh, Hwan Soo; Kim, Jun Sung; Semertzidis, Yannis K.; Lee, Jhinhwan

    Sr4V2O6Fe2As2 consists of superconducting FeAs layers and Mott insulating Sr2VO3 layers, and exhibits superconductivity with Tc near 30 K despite being a parent compound material. Unlike normal Fe-based superconductors, the magnetism of Sr4V2O6Fe2As2 has complexity due to the presence of two magnetic atomic layers of V and Fe; therefore, the issue of magnetism has been actively debated. In this work, we studied the orbital and magnetic phase transitions in the range of 4 K to 180 K using spin-polarized scanning tunneling microscope. We directly observed the changes of charge density waves of V atomic layer related to the nematicity at 150 K, and spin density waves of V atomic layer resulting from spin ordering of underlying Fe atomic layer below 50 K. Moreover, controlling the sample bias voltage, the hysteresis of magnetic domain is observed at 4 K. Our results show key clues to solve controversy about the magnetism of Sr4V2O6Fe2As2.

  1. Local Atomic Structure and Magnetism in Amorphous FexSi1-x Thin Films

    NASA Astrophysics Data System (ADS)

    Hellman, Frances; Zhang, Yanning; Bordel, Catherine; Stone, Kevin; Jenkins, Catherine; Smith, David; Hu, J.; Wu, Ruqian; Heald, Steve; Kortright, Jeff; Karel, Julie

    2014-03-01

    Amorphous FexSi1-x thin films exhibit a large enhancement in M compared to crystalline films with the same composition (0.45< x<0.75). XMCD shows enhancement in both spin and orbital moments. Density functional theory (DFT) calculations reproduce this enhanced magnetization. DFT and EXAFS show the amorphous materials have decreased number of nearest neighbors and reduced number density relative to crystalline samples of same x, which leads to the enhanced moment. Thanks to DOE BES LBNL magnetism program for support.

  2. Atomic-Scale Imaging and Control of Interface Magnetic States in Vacancy Ordered Cobaltite Thin Films

    NASA Astrophysics Data System (ADS)

    Borisevich, Albina; Kim, Young-Min; Biegalski, Michael; He, Jun; Christen, Hans; Pantelides, Sokrates; Pennycook, Stephen

    2012-02-01

    Magnetic properties of complex oxide thin films are strongly affected by strain, chemical composition, and octahedral tilt of the substrate. Here, we study lanthanum/strontium cobaltite (La0.5Sr0.5CoO3-x, LSCO) thin films via quantitative aberration-corrected scanning transmission electron microscopy and Electron Energy Loss Spectroscopy (EELS) to explore the coupling between magnetic properties, ionic behavior, and oxygen octahedral tilts. LSCO films were grown by PLD in identical conditions on two different substrates, LSAT (cubic) and NGO (orthorhombic). These substrates have nearly identical lattice parameters, but different octahedral tilts. The film on NGO appears to be La0.5Sr0.5CoO2.5, while the film on LSAT is less oxygen deficient. Comparison of measured lattice parameters with the first-principles calculations allows us to determine oxygen content in the film. In La0.5Sr0.5CoO2.5/NGO films, EELS reveals different valence states of Co at the interface depending on termination, resulting in different magnetic states. Therefore changes in octahedral tilts can induce changes in oxygen stoichiometry and interface magnetic states of the vacancy ordered structures.

  3. Defect propagation in one-, two-, and three-dimensional compounds doped by magnetic atoms

    SciTech Connect

    Furrer, A.; Podlesnyak, A.; Krämer, K. W.; Strässle, Th.

    2014-10-29

    Inelastic neutron scattering experiments were performed to study manganese(II) dimer excitations in the diluted one-, two-, and three-dimensional compounds CsMnxMg1-xBr3, K2MnxZn1-xF4, and KMnxZn1-xF3 (x≤0.10), respectively. The transitions from the ground-state singlet to the excited triplet, split into a doublet and a singlet due to the single-ion anisotropy, exhibit remarkable fine structures. These unusual features are attributed to local structural inhomogeneities induced by the dopant Mn atoms which act like lattice defects. Statistical models support the theoretically predicted decay of atomic displacements according to 1/r2, 1/r, and constant (for three-, two-, and one-dimensional compounds, respectively) where r denotes the distance of the displaced atoms from the defect. In conclusion, the observed fine structures allow a direct determination of the local exchange interactions J, and the local intradimer distances R can be derived through the linear law dJ/dR.

  4. Defect propagation in one-, two-, and three-dimensional compounds doped by magnetic atoms

    DOE PAGESBeta

    Furrer, A.; Podlesnyak, A.; Krämer, K. W.; Strässle, Th.

    2014-10-29

    Inelastic neutron scattering experiments were performed to study manganese(II) dimer excitations in the diluted one-, two-, and three-dimensional compounds CsMnxMg1-xBr3, K2MnxZn1-xF4, and KMnxZn1-xF3 (x≤0.10), respectively. The transitions from the ground-state singlet to the excited triplet, split into a doublet and a singlet due to the single-ion anisotropy, exhibit remarkable fine structures. These unusual features are attributed to local structural inhomogeneities induced by the dopant Mn atoms which act like lattice defects. Statistical models support the theoretically predicted decay of atomic displacements according to 1/r2, 1/r, and constant (for three-, two-, and one-dimensional compounds, respectively) where r denotes the distance ofmore » the displaced atoms from the defect. In conclusion, the observed fine structures allow a direct determination of the local exchange interactions J, and the local intradimer distances R can be derived through the linear law dJ/dR.« less

  5. Atomic-Scale Magnetism of Cr-Doped Bi2Se3 Thin Film Topological Insulators.

    PubMed

    Liu, Wenqing; West, Damien; He, Liang; Xu, Yongbing; Liu, Jun; Wang, Kejie; Wang, Yong; van der Laan, Gerrit; Zhang, Rong; Zhang, Shengbai; Wang, Kang L

    2015-10-27

    Magnetic doping is the most common method for breaking time-reversal-symmetry surface states of topological insulators (TIs) to realize novel physical phenomena and to create beneficial technological applications. Here we present a study of the magnetic coupling of a prototype magnetic TI, that is, Cr-doped Bi2Se3, in its ultrathin limit which is expected to give rise to quantum anomalous Hall (QAH) effect. The high quality Bi2-xCrxSe3 epitaxial thin film was prepared using molecular beam epitaxy (MBE), characterized with scanning transimission electron microscopy (STEM), electrical magnetotransport, and X-ray magnetic circularly dichroism (XMCD) techniques, and the results were simulated using density functional theory (DFT) with spin-orbit coupling (SOC). We observed a sizable spin moment mspin = (2.05 ± 0.20) μB/Cr and a small and negative orbital moment morb = (-0.05 ± 0.02) μB/Cr of the Bi1.94Cr0.06Se3 thin film at 2.5 K. A remarkable fraction of the (CrBi-CrI)(3+) antiferromagnetic dimer in the Bi2-xCrxSe3 for 0.02 < x < 0.40 was obtained using first-principles simulations, which was neglected in previous studies. The spontaneous coexistence of ferro- and antiferromagnetic Cr defects in Bi2-xCrxSe3 explains our experimental observations and those based on conventional magnetometry which universally report magnetic moments significantly lower than 3 μB/Cr predicted by Hund's rule. PMID:26348798

  6. The low-temperature magnetism of cerium atoms in CeMn2Si2 and CeMn2Ge2 compounds

    NASA Astrophysics Data System (ADS)

    Lalic, Milan V.; Mestnik-Filho, José; Carbonari, Artur W.; Saxena, Rajendra N.

    2004-09-01

    The low-temperature magnetic properties of the Ce atoms in the intermetallic compounds CeMn2Ge2 and CeMn2Si2 were studied. Previous neutron scattering measurements did not detect an ordered moment at Ce atoms in either compound despite the fact that they are surrounded by the Mn moments ordered ferromagnetically in the CeMn2Ge2 and antiferromagnetically in the CeMn2Si2. Contrasting with this result, a recent measurement performed with the time differential perturbed angular correlation (TDPAC) technique showed the presence of a pronounced magnetic hyperfine field (MHF) at Ce sites in the CeMn2Ge2 compound and no MHF in CeMn2Si2. The absence of the Ce magnetic moment and MHF in the silicide can be understood in terms of too weak a Ce-Ce magnetic interaction while in the germanide the TDPAC result suggests that some magnetic ordering of Ce atoms may occur. Aiming to understand the effects which result in the quenching of the Ce 4f moment in both cases, we performed first-principles band-structure calculations for both systems, using the full potential linear augmented plane wave method. It is shown that the magnetism of the Ce sublattice has fundamentally different nature in CeMn2Si2 and CeMn2Ge2. While the Ce atoms are intrinsically non-magnetic in the silicide, having a zero magnetic moment with both spin and orbital contributions identically zero, they display magnetic properties in the CeMn2Ge2 since their very small total moment is composed of finite spin and orbital components which almost cancel each other accidentally.

  7. Magnetic Properties of a Single-Molecule Lanthanide-Transition-Metal Compound Containing 52 Gadolinium and 56 Nickel Atoms.

    PubMed

    Liu, Da-Peng; Lin, Xin-Ping; Zhang, Hui; Zheng, Xiu-Ying; Zhuang, Gui-Lin; Kong, Xiang-Jian; Long, La-Sheng; Zheng, Lan-Sun

    2016-03-24

    Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core-shell structure of the monodisperse molecule magnet of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]@SiO2 (1 a@SiO2 ) was prepared by encapsulating one high-nuclearity lanthanide-transition-metal compound of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]⋅(NO3 )18 ⋅164 H2 O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one-pot microemulsion method. 1 a@SiO2 was characterized using transmission electron microscopy, N2 adsorption-desorption isotherms, and inductively coupled plasma-atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1 =0.25 cm(-1) , J2 =-0.060 cm(-1) , J3 =-0.22 cm(-1) , J4 =-8.63 cm(-1) , g=1.95, and z J=-2.0×10(-3)  cm(-1) for 1, and J1 =0.26 cm(-1) , J2 =-0.065 cm(-1) , J3 =-0.23 cm(-1) , J4 =-8.40 cm(-1)  g=1.99, and z J=0.000 cm(-1) for 1 a@SiO2 . The z J=0 in 1 a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres. PMID:26923173

  8. Enhanced magnetization in highly crystalline and atomically mixed bcc Fe-Co nanoalloys prepared by hydrogen reduction of oxide composites

    NASA Astrophysics Data System (ADS)

    Sharif, Md Jafar; Yamauchi, Miho; Toh, Shoichi; Matsumura, Syo; Noro, Shin-Ichiro; Kato, Kenichi; Takata, Masaki; Tsukuda, Tatsuya

    2013-01-01

    FexCo100-x nanoalloys (NAs) with 20 <= x <= 80 were prepared by hydrogen reduction of Fe-Co oxide nano-composites, which were composed of mixed phases (or domains) of Fe2O3 and CoO. In situ X-ray diffraction (XRD) measurements using synchrotron radiation clearly showed development of a solid-solution Fe-Co phase by hydrogen reduction from the oxide composites. High-resolution transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM and powder XRD revealed that Fe-Co NAs form a single crystal structure and the two elements are mixed homogeneously. The saturation magnetization depends on the size and metal composition and shows the highest value (250 emu g-1) for the Fe70Co30 NA in the size range of 30-55 nm, which is comparable to that of the Fe70Co30 bulk alloy (245 emu g-1). This high magnetization is attributable to high crystallinity and homogeneous mixing of constituent atoms, which are attained by thermal treatment of oxide phases under a hydrogen atmosphere.FexCo100-x nanoalloys (NAs) with 20 <= x <= 80 were prepared by hydrogen reduction of Fe-Co oxide nano-composites, which were composed of mixed phases (or domains) of Fe2O3 and CoO. In situ X-ray diffraction (XRD) measurements using synchrotron radiation clearly showed development of a solid-solution Fe-Co phase by hydrogen reduction from the oxide composites. High-resolution transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM and powder XRD revealed that Fe-Co NAs form a single crystal structure and the two elements are mixed homogeneously. The saturation magnetization depends on the size and metal composition and shows the highest value (250 emu g-1) for the Fe70Co30 NA in the size range of 30-55 nm, which is comparable to that of the Fe70Co30 bulk alloy (245 emu g-1). This high magnetization is attributable to high crystallinity and homogeneous mixing of constituent atoms, which are attained by thermal treatment of oxide phases under a hydrogen

  9. Direct measurements of the magnetic field induced by optically polarized sup 3 He atoms

    SciTech Connect

    Gudoshnikov, S.A.; Snigirev, O.V. ); Kozlov, A.N.; Maslennikov, Y.V.; Serebrjakov, A.Y. )

    1991-03-01

    This paper reports on an alternative magnetic field induced by the standard cell of the optically pumped {sup 3}He magnetometer directly measured by the SQUID-based second-order gradiometer with signal-to-noise ratio higher than 6. The magnitude of the measured field equal to 5 {times} 10{sup {minus}13} T at the 5-cm distance from the cell axis and transverse relaxation time T{sub 2} equal to 7 minutes have been found.

  10. Interaction transfer of silicon atoms forming Co silicide for Co/√(3)×√(3)R30°-Ag/Si(111) and related magnetic properties

    SciTech Connect

    Chang, Cheng-Hsun-Tony; Fu, Tsu-Yi; Tsay, Jyh-Shen

    2015-05-07

    Combined scanning tunneling microscopy, Auger electron spectroscopy, and surface magneto-optic Kerr effect studies were employed to study the microscopic structures and magnetic properties for ultrathin Co/√(3)×√(3)R30°-Ag/Si(111). As the annealing temperature increases, the upward diffusion of Si atoms and formation of Co silicides occurs at temperature above 400 K. Below 600 K, the √(3)×√(3)R30°-Ag/Si(111) surface structure persists. We propose an interaction transferring mechanism of Si atoms across the √(3)×√(3)R30°-Ag layer. The upward transferred Si atoms react with Co atoms to form Co silicide. The step height across the edge of the island, a separation of 0.75 nm from the analysis of the 2 × 2 structure, and the calculations of the normalized Auger signal serve as strong evidences for the formation of CoSi{sub 2} at the interface. The interaction transferring mechanism for Si atoms enhances the possibility of interactions between Co and Si atoms. The smoothness of the surface is advantage for that the easy axis of magnetization for Co/√(3)×√(3)R30°-Ag/Si(111) is in the surface plane. This provides a possible way of growing flat magnetic layers on silicon substrate with controllable silicide formation and shows potential applications in spintronics devices.

  11. Atomic and magnetic order in the shape memory alloy Mn2NiGa

    NASA Astrophysics Data System (ADS)

    Brown, P. J.; Kanomata, T.; Neumann, K.; Neumann, K. U.; Ouladdiaf, B.; Sheikh, A.; Ziebeck, K. R. A.

    2010-12-01

    Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory alloy Mn2NiGa have confirmed that it is ferromagnetic with a Curie temperature above 500 K. The compound undergoes a broad structural phase transformation ΔT ~ 90 K with a mean transition temperature TM ~ 270 K. The high temperature parent phase is cubic (a = 5.937 Å) and has a modified L 21 structure. At 500 K the ordered magnetic moment essentially all on the 4a site is 1.35 μB/Mn. The low temperature martensite has space group I4/mmm and is related to the cubic phase through a Bain transformation atet = (acub + bcub)/2, btet = (acub - bcub) and ctet = ccub in which the change in cell volume is < 2.6%. In this structure at 5 K the ordered moment of ≈2.3 μB is again found to be confined to the sites with full Mn occupation and is aligned parallel to c. Neutron diffraction patterns obtained at 5 K suggested the presence of a weak incommensurate antiferromagnetic phase characterized by either a (\\frac 13 0 \\frac 13) or (0 0 \\frac 13) propagation vector.

  12. In situ study of atomic-vacancy ordering in stoichiometric titanium monoxide by the magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Valeeva, A. A.; Nazarova, S. Z.; Rempel, A. A.

    2015-02-01

    An in situ temperature study of a variation in the degree of long-range order in stoichiometric titanium monoxide has been performed by the magnetic susceptibility method. The measurements have been performed on annealed and quenched titanium monoxide in the temperature range from 300 to 1200 K. It has been found that the degree of long-range order depends on the regime and temperature of annealing of the initial samples. The degree of long-range order in the process of measurement of the magnetic susceptibility varies from 0.21 to 1.00; the larger the degree of long-range order, the smaller the magnetic susceptibility. Furthermore, the long-range order parameter decreases with an increase in the temperature above 1200 K and vanishes sharply at the order-disorder transition temperature. According to the results of this work, the critical long-range order parameter is 0.21 and the temperature of the nonequilibrium disorder-order transition is about 1073 K.

  13. Scaling properties of composite information measures and shape complexity for hydrogenic atoms in parallel magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    González-Férez, R.; Dehesa, J. S.; Patil, S. H.; Sen, K. D.

    2009-12-01

    The scaling properties of various composite information-theoretic measures (Shannon and Rényi entropy sums, Fisher and Onicescu information products, Tsallis entropy ratio, Fisher-Shannon product and shape complexity) are studied in position and momentum spaces for the non-relativistic hydrogenic atoms in the presence of parallel magnetic and electric fields. Such measures are found to be invariant at the fixed values of the scaling parameters given by s1={Bħ3(4}/{Z2m2e} and s2={Fħ4(4}/{Z3em2}. Numerical results which support the validity of the scaling properties are shown by choosing the representative example of the position space shape complexity. Physical significance of the resulting scaling behavior is discussed.

  14. Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid

    NASA Astrophysics Data System (ADS)

    Hoof, Sebastian; Nand Gosvami, Nitya; Hoogenboom, Bart W.

    2012-12-01

    Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here, we show that a high-quality resonance (Q >20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity—as expressed via the minimum detectable force gradient—is hardly affected, because of the enhanced quality factor. Through the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up that includes magnetic actuation of the cantilevers and that can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

  15. Novel ion imprinted magnetic mesoporous silica for selective magnetic solid phase extraction of trace Cd followed by graphite furnace atomic absorption spectrometry detection

    NASA Astrophysics Data System (ADS)

    Zhao, Bingshan; He, Man; Chen, Beibei; Hu, Bin

    2015-05-01

    Determination of trace Cd in environmental, biological and food samples is of great significance to toxicological research and environmental pollution monitoring. While the direct determination of Cd in real-world samples is difficult due to its low concentration and the complex matrix. Herein, a novel Cd(II)-ion imprinted magnetic mesoporous silica (Cd(II)-II-MMS) was prepared and was employed as a selective magnetic solid-phase extraction (MSPE) material for extraction of trace Cd in real-world samples followed by graphite furnace atomic absorption spectrometry (GFAAS) detection. Under the optimized conditions, the detection limit of the proposed method was 6.1 ng L- 1 for Cd with the relative standard deviation (RSD) of 4.0% (c = 50 ng L- 1, n = 7), and the enrichment factor was 50-fold. To validate the proposed method, Certified Reference Materials of GSBZ 50009-88 environmental water, ZK018-1 lyophilized human urine and NIES10-b rice flour were analyzed and the determined values were in a good agreement with the certified values. The proposed method exhibited a robust anti-interference ability due to the good selectivity of Cd(II)-II-MMS toward Cd(II). It was successfully employed for the determination of trace Cd(II) in environmental water, human urine and rice samples with recoveries of 89.3-116%, demonstrating that the proposed method has good application potential in real world samples with complex matrix.

  16. DFT modelling of the [M-Pd-M] 6+ metal atom chains (M = Ni, Pd): Structural, electronic and magnetic issues

    NASA Astrophysics Data System (ADS)

    López, Xavier; Rohmer, Marie-Madeleine; Bénard, Marc

    2008-11-01

    Following the recent findings on heterometallic string complexes, we extend the recently published work on NiPdNi(dpa) 4Cl 2 to discuss the Ni-Pd-Ni and Pd 3 chains with equatorial ligands (L) being dipyridylamide (dpa), 2,6-bis(phenylamido)pyridine (BPAP) and N, N'-bis-( p-toluenesulfonyl)-pyridyldiamide (Lpts), using the DFT formalism. The analysis of such a hypothetical series of linear trimetallics anticipates that, for NiPdNi(dpa) 4Cl 2, the extended valence shell of palladium strengthens the antiferromagnetic coupling between high-spin terminal nickel atoms. For L = BPAP the system, as expected, becomes diamagnetic, and antiferromagnetism reappears for L = Lpts. The theoretical modelling of the coupling following the Heisenberg Hamiltonian applied to two magnetic centres (H^=-2JS·S) gives -2 J = 320 and 497 cm -1 for L = dpa and Lpts, respectively. Pd 3 chains display an enhanced tendency to be diamagnetic with various ligands. More specifically with dpa, Pd 3(dpa) 4Cl 2—should it be synthesized—could be magnetically inactive since the strongly antiferromagnetic state generated by the coupling of two terminal, high-spin Pd atoms (-2 J = 1393 cm -1) is computed to be in close competition with the diamagnetic, closed-shell state. For L = Lpts as for BPAP, the hypothetic [Pd 3] 6+ chain is predicted to be diamagnetic, resulting from the high energy of the antibonding d(Pd)-p(N) orbital. The shift toward diamagnetism induced by the replacement of Ni by Pd in terminal position is therefore assigned to a stronger N → M donation interaction with M = Pd.

  17. Fe{sub 2-x}Co{sub x}MnSi (x = 0, 1 and 2) Heusler alloys: Structural, magnetic and atomic site disorder properties

    SciTech Connect

    Bhatt, Harsh; Mukadam, M. D.; Meena, S. S.; Yusuf, S. M.

    2015-06-24

    The Heusler alloy series Fe{sub 2-x}Co{sub x}MnSi (x = 0, 1 and 2) is theoretically predicted to be half metallic. We prepared the sample series and determined the structural and magnetic properties to check if these materials are suitable for spintronics applications. The Curie temperatures of two of the alloys have been found to be well above the room temperature. But the presence of elements with atoms of similar size leads to atomic site disorder in these alloys, which may destroy the half metallic nature. The atomic site disorder has been confirmed by Mössbauer spectroscopy.

  18. Electrical and mechanical controlling of the kinetic and magnetic properties of hydrogen atoms on free-standing silicene.

    PubMed

    Podsiadły-Paszkowska, Agata; Krawiec, Mariusz

    2016-07-20

    Effects of strain, charge doping and external electric field on kinetic and magnetic properties of hydrogen atoms on a free-standing silicene layer are investigated by first-principles density functional theory. It was found that the charge doping and strain are the most effective ways of changing the hydrogen-silicene binding energy, but they can only raise its value. The perpendicular external electric field can also lower it albeit in a narrower range. The strain has also the strongest impact on diffusion processes, and the diffusion barrier can be modified up to 50% of its unstrained value. The adsorption of hydrogen atoms results in a locally antiferromagnetic ground state with the effective exchange constant of approximately 1 eV. The system can easily be driven into a nonmagnetic phase by the charge doping and strain. The obtained results are very promising in view of the silicene functionalization and potential applications of silicene in fields of modern nanoelectronics and spintronics. PMID:27228502

  19. Electrical and mechanical controlling of the kinetic and magnetic properties of hydrogen atoms on free-standing silicene

    NASA Astrophysics Data System (ADS)

    Podsiadły-Paszkowska, Agata; Krawiec, Mariusz

    2016-07-01

    Effects of strain, charge doping and external electric field on kinetic and magnetic properties of hydrogen atoms on a free-standing silicene layer are investigated by first-principles density functional theory. It was found that the charge doping and strain are the most effective ways of changing the hydrogen-silicene binding energy, but they can only raise its value. The perpendicular external electric field can also lower it albeit in a narrower range. The strain has also the strongest impact on diffusion processes, and the diffusion barrier can be modified up to 50% of its unstrained value. The adsorption of hydrogen atoms results in a locally antiferromagnetic ground state with the effective exchange constant of approximately 1 eV. The system can easily be driven into a nonmagnetic phase by the charge doping and strain. The obtained results are very promising in view of the silicene functionalization and potential applications of silicene in fields of modern nanoelectronics and spintronics.

  20. Rovibrational molecular populations, atoms, and negative ions in H/sub 2/ and D/sub 2/ magnetic multicusp discharges

    SciTech Connect

    Pealat, M.; Taran, J.E.; Bacal, M.; Hillion, F.

    1985-06-01

    Coherent anti-Stokes Raman scattering is applied to the study of rovibrational populations in magnetic multicusp H/sub 2/ and D/sub 2/ discharges. This subject is of interest to negative hydrogen ion formation by volume plasma processes. The populations of high-lying rotational states (J>5) in the vibrational levels v = 0, 1, and 2 are found to be significantly higher than expected from the Boltzmann law. In H/sub 2/ the net populations of the first four vibrational levels follow approximately the Boltzmann law, with the vibrational temperature of 2390 K (in a 90 V-10 A discharge at 55 ..mu..bar). In similar discharge conditions, the population of the state v = 3 in D/sub 2/ is higher than expected from the Boltzmann law. In the presence of the discharge a deficiency in H/sub 2/ and D/sub 2/ molecule density was observed and was attributed to the possible presence of H and D atoms. This was verified by an independent measurement of the atomic fraction and temperature. The density of negative ions, measured by the photodetachment technique, is also reported.

  1. Two-dimensional pseudospectral Hartree-Fock method for low-Z atoms in intense magnetic fields

    NASA Astrophysics Data System (ADS)

    Thirumalai, Anand; Heyl, Jeremy S.

    2014-05-01

    The energy levels of the first few low-lying states of helium and lithium atoms in intense magnetic fields up to ≈108-109 T are calculated in this study. A pseudospectral method is employed for the computational procedure. The methodology involves computing the eigenvalues and eigenvectors of the generalized two-dimensional Hartree-Fock partial differential equations for these two- and three-electron systems in a self-consistent manner. The method exploits the natural symmetries of the problem without assumptions of any basis functions for expressing the wave functions of the electrons or the commonly employed adiabatic approximation. It is found that the results obtained here for a few of the most tightly bound states of each of the atoms, helium and lithium, are in good agreement with findings elsewhere. In this regard, we report data for two states of lithium that were lacking thus far. It is also seen that the pseudospectral method employed here is considerably more economical, from a computational point of view, than previously employed methods such as a finite-element-based approach. The key enabling advantage of the method described here is the short computational times, which are on the order of seconds for obtaining accurate results for heliumlike systems.

  2. Liquids in multiorbital SU(N) magnets made up of ultracold alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Xu, Cenke

    2010-04-01

    In this work we study one family of liquid states of k -orbital SU(N) spin systems, focusing on the case of k=2 which can be realized by ultracold alkaline-earth atoms trapped in optical lattices, with N as large as 10. Five different algebraic liquid states with selectively coupled charge, spin, and orbital quantum fluctuations are considered. The algebraic liquid states can be stabilized with large enough N and the scaling dimension of physical order parameters is calculated using a systematic 1/N expansion. The phase transitions between these liquid states are also studied and all the algebraic liquid states discussed in this work can be obtained from one “mother” state with SU(2)×U(1) gauge symmetry.

  3. Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

    PubMed Central

    Kraus, H.; Soltamov, V. A.; Fuchs, F.; Simin, D.; Sperlich, A.; Baranov, P. G.; Astakhov, G. V.; Dyakonov, V.

    2014-01-01

    Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these centers very attractive for vector magnetometry. Contrarily, the zero-field splitting of another center exhibits a giant thermal shift of −1.1 MHz/K at room temperature, which can be used for thermometry applications. We also discuss a synchronized composite clock exploiting spin centers with different thermal response. PMID:24993103

  4. The magnetic and transport properties of edge passivated silicene nanoribbon by Mn atoms

    NASA Astrophysics Data System (ADS)

    Chen, Changpeng; Zhu, Ziqing; Zha, Dace; Qi, Meilan; Wu, Jinping

    2016-02-01

    The effect of chemical doping on the ZSiNRs with Mn as passivating element replacing H atoms at one edge are investigated by first-principles calculations. The structures optimized in the typical ferromagnetic and antiferromagnetic coupling show that the system leads to an AFM state and achieve half-metallic properties. Also, our first principle approach based on the Keldysh non-equilibrium Green's function method gives the spin-dependent transport properties of the device. When the system changes from parallel to antiparallel configuration. The spin-up current increases rapidly while the spin-up current is still depressed. Further, it is found that the system is a quite good spin filtering device with nearly 80% spin filtering efficiency at a wide bias voltage region and therefore suitable for applications. The mechanisms for these phenomena are proposed in detail.

  5. Adsorption of Ti atoms on zigzag silicene nanoribbons: influence on electric, magnetic, and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Xu, Long; Wang, Xue-Feng; Zhou, Liping; Yang, Zhi-Yong

    2015-06-01

    We study the adsorption effects of Ti atoms on the physical properties of zigzag silicene nanoribbons using the density functional theory combined with the nonequilibrium Green’s function methods. The adsorption geometries, conductance spectra, current voltage curves, spin polarizations, magnetoresistance, and Seebeck coefficients are evaluated in different adsorption samples. Ti adatoms prefer sites inside the nanoribbons instead of on the edges. Two neighboring adatoms are attractively coupled and prefer being adsorbed on the same side. The giant magnetoresistance in nanoribbons of even width is usually greatly reduced, except in symmetric adsorption cases. Strong spin negative differential resistance phenomena can be observed and pure spin current can be produced by temperature gradient in specific cases.

  6. Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

    NASA Astrophysics Data System (ADS)

    Kraus, H.; Soltamov, V. A.; Fuchs, F.; Simin, D.; Sperlich, A.; Baranov, P. G.; Astakhov, G. V.; Dyakonov, V.

    2014-07-01

    Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these centers very attractive for vector magnetometry. Contrarily, the zero-field splitting of another center exhibits a giant thermal shift of -1.1 MHz/K at room temperature, which can be used for thermometry applications. We also discuss a synchronized composite clock exploiting spin centers with different thermal response.

  7. Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms

    NASA Astrophysics Data System (ADS)

    Frisch, P. C.; Berdyugin, A.; Piirola, V.; Magalhaes, A. M.; Seriacopi, D. B.; Wiktorowicz, S. J.; Andersson, B.-G.; Funsten, H. O.; McComas, D. J.; Schwadron, N. A.; Slavin, J. D.; Hanson, A. J.; Fu, C.-W.

    2015-12-01

    The interstellar magnetic field (ISMF) near the heliosphere is a fundamental component of the solar galactic environment that can only be studied using polarized starlight. The results of an ongoing survey of the linear polarizations of local stars are analyzed with the goal of linking the ISMF that shapes the heliosphere to the nearby field in interstellar space. We present new results on the direction of the magnetic field within 40 pc obtained from analyzing polarization data using a merit function that determines the field direction that provides the best fit to the polarization data. Multiple magnetic components are identified, including a dominant interstellar field, {B}{POL}, that is aligned with the direction ℓ, b = 36.°2, 49.°0 (±16.°0). Stars tracing {B}{POL} have the same mean distance as stars that do not trace {B}{POL}, but show weaker average polarizations consistent with a smaller column density of polarizing material. {B}{POL} is aligned with the ISMF traced by the IBEX Ribbon to within {7.6}-7.6+14.9 degrees. The variations in the polarization position angle directions derived from the data that best match {B}{POL} indicate a low level of magnetic turbulence, ˜9° ± 1°. The direction of {B}{POL} is obtained after excluding polarization data tracing a separate magnetic structure that appears to be associated with interstellar dust deflected around the heliosphere. The velocities of local interstellar clouds relative to the Local Standard of Rest (LSR) increase with the angles between the LSR velocities and {B}{POL}, indicating that the kinematics of local interstellar material is ordered by the ISMF. The Loop I superbubble that extends close to the Sun contains dust that reddens starlight and whose distance is determined by the color excess E(B - V) of starlight. Polarizations caused by grains aligned with respect to {B}{POL} are consistent with the location of the Sun in the rim of the Loop I superbubble. An angle of {76

  8. Scanning tunneling spectroscopy of a magnetic atom on graphene in the Kondo regime

    DOE PAGESBeta

    Zhuang, Huai -Bin; Sun, Qing -feng; Xie, X. C.

    2009-06-23

    In this study, the Kondo effect in the system consisting of a magnetic adatom on the graphene is studied. By using the non-equilibrium Green function method with the slave-boson mean field approximation, the local density of state (LDOS) and the conductance are calculated. For a doped graphene, the Kondo phase is present at all time. Surprisingly, two kinds of Kondo regimes are revealed. But for the undoped graphene, the Kondo phase only exists if the adatom’s energy level is beyond a critical value. The conductance is similar to the LDOS, thus, the Kondo peak in the LDOS can be observedmore » with the scanning tunneling spectroscopy. In addition, in the presence of a direct coupling between the STM tip and the graphene, the conductance may be dramatically enhanced, depending on the coupling site.« less

  9. Scanning tunneling spectroscopy of a magnetic atom on graphene in the Kondo regime

    SciTech Connect

    Zhuang, Huai -Bin; Sun, Qing -feng; Xie, X. C.

    2009-06-23

    In this study, the Kondo effect in the system consisting of a magnetic adatom on the graphene is studied. By using the non-equilibrium Green function method with the slave-boson mean field approximation, the local density of state (LDOS) and the conductance are calculated. For a doped graphene, the Kondo phase is present at all time. Surprisingly, two kinds of Kondo regimes are revealed. But for the undoped graphene, the Kondo phase only exists if the adatom’s energy level is beyond a critical value. The conductance is similar to the LDOS, thus, the Kondo peak in the LDOS can be observed with the scanning tunneling spectroscopy. In addition, in the presence of a direct coupling between the STM tip and the graphene, the conductance may be dramatically enhanced, depending on the coupling site.

  10. Warm Up with Skill.

    ERIC Educational Resources Information Center

    Hoyle, R. J.; Smith, Robert F.

    1989-01-01

    Too little time is often spent on warm-up activities in the school or recreation class. Warm-ups are often perfunctory and unimaginative. Several suggestions are made for warm-up activities that incorporate both previously learned and new skills, while preparing the body for more vigorous activity. (IAH)

  11. Helical order in one-dimensional magnetic atom chains and possible emergence of Majorana bound states

    NASA Astrophysics Data System (ADS)

    Kim, Younghyun; Cheng, Meng; Bauer, Bela; Lutchyn, Roman M.; Das Sarma, S.

    2014-08-01

    We theoretically obtain the phase diagram of localized magnetic impurity spins arranged in a one-dimensional chain on top of a one- or two-dimensional electron gas. The interactions between the spins are mediated by the Ruderman-Kittel-Kasuya-Yosida mechanism through the electron gas. Recent work predicts that such a system may intrinsically support topological superconductivity without spin-orbit coupling when a helical spin-density wave is spontaneously formed in the spins, and superconductivity is induced in the electron gas. We analyze, using both analytical and numerical techniques, the conditions under which such a helical spin state is stable in a realistic situation in the presence of disorder. We show that (i) it appears only when the spins are coupled to a (quasi-) one-dimensional electron gas, and (ii) it becomes unstable towards the formation of (anti)ferromagnetic domains if the disorder in the impurity spin positions δR becomes comparable with the Fermi wavelength. We also examine the stability of the helical state against Gaussian potential disorder in the electronic system using a diagrammatic approach. Our results suggest that in order to stabilize the helical spin state and thus the emergent topological superconductivity under realistic experimental conditions, a sufficiently strong Rashba spin-orbit coupling, giving rise to Dzyaloshinskii-Moriya interactions, is required.

  12. Magnetic-field-induced electric quadrupole moments for relativistic hydrogenlike atoms: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function

    NASA Astrophysics Data System (ADS)

    Stefańska, Patrycja

    2016-02-01

    We consider a Dirac one-electron atom placed in a weak, static, uniform magnetic field. We show that, to the first order in the strength B of the external field, the only electric multipole moments, which are induced by the perturbation in the atom, are those of an even order. Using the Sturmian expansion of the generalized Dirac-Coulomb Green function [R. Szmytkowski, J. Phys. B 30, 825 (1997), 10.1088/0953-4075/30/4/007; J. Phys. B 30, 2747 (1997), 10.1088/0953-4075/30/11/023], We derive a closed-form expression for the electric quadrupole moment induced in the atom in an arbitrary discrete energy eigenstate. The result, which has the form of a double finite sum involving the generalized hypergeometric functions 3F2 of the unit argument, agrees with the earlier relativistic formula for that quantity, obtained by us for the ground state of the atom.

  13. Chiral and magnetic rotation in atomic nuclei studied within self-consistent mean-field methods

    NASA Astrophysics Data System (ADS)

    Olbratowski, P.

    2004-07-01

    Currently, one application of the mean-field methods in nuclear physics is the investigation of exotic nuclear symmetries. This is related, in particular, to the study of nuclear rotation about an axis tilted with respect to the principal axes of the mass distribution in the Tilted-Axis Cranking (TAC) model. The present work presents one of the first TAC calculations performed within fully self-consistent methods. The Hartree-Fock method with the Skyrme effective two-body interaction has been used. A computer code has been developed that allows for the breaking of all spatial symmetries of the solution. As a first application, calculations for the magnetic bands in 142Gd and for the chiral bands in 130Cs, 132La, 134Pr, and 136Pm have been carried out. The appearance of those bands is due to a new mechanism of breaking the spherical symmetry and to the spontaneous breaking of the chiral symmetry, respectively. The self-consistent solutions for 142Gd confirm the important role of the shears mechanism in generating the total angular momentum. However, the agreement with experimental data is not satisfactory, probably due to the lack of the pairing correlations in the calculations or to the possibly overestimated deformation. The results obtained for 132La constitute the first fully self-consistent proof that the nuclear rotation can attain a chiral character. It has been shown that the chiral rotation can only exist above a certain critical angular frequency. It has also been checked that the terms of the Skyrme mean field odd under the time reversal have no qualitative influence on the results.

  14. Influence of the critical Fe atomic volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements

    NASA Astrophysics Data System (ADS)

    Kiss, L. F.; Kemény, T.; Bednarčík, J.; Gamcová, J.; Liermann, H.-P.

    2016-06-01

    Despite the intensive studies for decades, it is still not well understood how qualitatively different magnetic behaviors can occur in a narrow composition range for the Fe-rich Fe-transition metal (TM) amorphous alloys. In this study of amorphous F e100 -xZ rx (x =7 , 9, 12) metallic glasses, normal ferromagnetism (FM) is found at 12 % Zr where only the FM-paramagnetic (PM) transition is observed at the Curie temperature, TC. In contrast, spin-glass (SG)-PM transition at a temperature, Tg, called SG temperature, is only observed at 7 % Zr, while in the transient re-entrant composition range (x =8 -11 ) , an SG-FM transition at a temperature, Tf, called spin-freezing temperature, is also observed at low temperature besides the normal FM-PM transition at TC. In order to understand this unusual behavior, a detailed characterization of pressure (atomic volume), composition, and temperature dependence of the magnetic properties is coupled with high pressure synchrotron x-ray diffraction determination of the pressure dependence of the atomic volume. The results on F e100 -xZ rx (x =7 , 9, 12) are compared to those obtained for the FM C o91Z r9 metallic glass not showing any kind of anomalous magnetic properties. It is confirmed that the unusual behavior is caused by a granularlike magnetic structure where weakly coupled magnetic clusters are embedded into a FM bulk matrix. Since the mechanism of the magnetization reversal was found to be of the curling type rather than homogeneous rotation, the energy barrier determining the blocking temperature of the clusters is calculated as AR, where A is the exchange constant and R is the cluster size, in contrast to the usual characterization of the energy barrier by KV where K is the anisotropy energy and V is the cluster volume. The volume fraction of the FM part is a fast changing function of the bulk composition: Almost 100% FM fraction is found at 12 % of Zr while no trace of real FM is observed at 7 at % Zr. The driving

  15. Warm dense crystallography

    NASA Astrophysics Data System (ADS)

    Valenza, Ryan A.; Seidler, Gerald T.

    2016-03-01

    The intense femtosecond-scale pulses from x-ray free electron lasers (XFELs) are able to create and interrogate interesting states of matter characterized by long-lived nonequilibrium semicore or core electron occupancies or by the heating of dense phases via the relaxation cascade initiated by the photoelectric effect. We address here the latter case of "warm dense matter" (WDM) and investigate the observable consequences of x-ray heating of the electronic degrees of freedom in crystalline systems. We report temperature-dependent density functional theory calculations for the x-ray diffraction from crystalline LiF, graphite, diamond, and Be. We find testable, strong signatures of condensed-phase effects that emphasize the importance of wide-angle scattering to study nonequilibrium states. These results also suggest that the reorganization of the valence electron density at eV-scale temperatures presents a confounding factor to achieving atomic resolution in macromolecular serial femtosecond crystallography (SFX) studies at XFELs, as performed under the "diffract before destroy" paradigm.

  16. On the electronic and magnetic properties of nanostructures, solids and cold atomic gases

    NASA Astrophysics Data System (ADS)

    Sau, Jay Deep

    technique to determine the level alignment and gaps of a molecule in the neighborhood of a substrate. We then test our method by quantitatively comparing the results of this method applied to the C 60 molecule on Au and Ag substrates to experimental scanning tunneling spectroscopy results on these systems. (6) In chapter six we move our focus to bulk systems and use a combination of density functional theory and empirical pseudopotential methods to study the transport properties of Ge-Sn alloy systems. Using the empirical pseudopotential method we find a combination of strain and alloying that turns Ge-Sn into a direct gap semiconductor with low electron and hole masses. The low effective masses implies an increased carrier mobility for the alloy. Using density functional theory calculations we calculate the effect of alloy scattering from Sn in Ge and show that even after taking into account substitutional disorder from alloy scattering Ge-Sn alloys are expected to exhibit higher mobilities than Ge. (7) In the final chapter we apply the combination of a model Hamiltonian and a computational solution of mean field equations that we have been applying to solid state systems to understand and predict the properties of ultra-cold spinor Bose Eintein Condensates. In this study we study the effect of how dipole-dipole interactions between spin-1 Rubidium atoms can directly affect the dynamics of quantum noise induced domain formation and predict ways to directly observe the dipole-dipole interactions between 87Rb.

  17. Matrix-assisted laser desorption using a fast-atom bombardment ion source and a magnetic mass spectrometer.

    PubMed

    Annan, R S; Köchling, H J; Hill, J A; Biemann, K

    1992-04-01

    A conventional fast-atom bombardment (FAB) ion source was used to achieve matrix-assisted laser desorption (MALD) in a high-mass, double-focusing, magnetic mass spectrometer. The pulsed ion signals generated by irradiation of a mixture of sample and matrix (2,5-dihydroxybenzoic acid) with either a XeF excimer laser (353 nm) or a nitrogen laser (337 nm) were recorded with a focal-plane detector. A resolution (full-width at half maximum) of 4500 was achieved at m/z 1347.7 (the peptide substance P), 2500 for CsI cluster ions at m/z 10,005.7, and 1250 for the isotope cluster of the small protein cytochrome c (horse) [M+H]+ = m/z 12,360 (average). Sensitivity is demonstrated with 11 fmol of substance P. A survey scan is taken to locate the m/z of the sample molecular ion. The segment that contains the sample can then be integrated for a longer time to produce a better signal-to-noise ratio. In addition to higher sensitivity and lower matrix interference, the advantage of MALD over FAB is the former's lower susceptibility to the presence of salts, and competition between hydrophobic and hydrophilic components of a mixture. This feature is demonstrated by the complete MALD spectrum of a crude partial tryptic digest of sperm-whale apomyoglobin, containing 24 peptides, representing the entire sequence of this protein. PMID:1373978

  18. Viscoelastic measurements of single molecules on a millisecond time scale by magnetically driven oscillation of an atomic force microscope cantilever.

    PubMed

    Kawakami, Masaru; Byrne, Katherine; Khatri, Bhavin S; Mcleish, Tom C B; Radford, Sheena E; Smith, D Alastair

    2005-05-10

    The dynamical nature of biomolecular systems means that knowledge of their viscoelastic behavior is important in fully understanding function. The linear viscoelastic response can be derived from an analysis of Brownian motion. However, this is a slow measurement and technically demanding for many molecular systems of interest. To address this issue, we have developed a simple method for measuring the full linear viscoelastic response of single molecules based on magnetically driven oscillations of an atomic force microscope cantilever. The cantilever oscillation frequency is periodically swept through the system resonance in less than 200 ms allowing the power spectrum to be obtained rapidly and analyzed with a suitable model. The technique has been evaluated using dextran, a polysaccharide commonly used as a test system for single molecule mechanical manipulation experiments. The monomer stiffness and friction constants were compared with those derived from other methods. Excellent agreement is obtained indicating that the new method accurately and, most importantly, rapidly provides the viscoelastic response of a single molecule between the tip and substrate. The method will be a useful tool for studying systems that change their structure and dynamic response on a time scale of 100-200 ms, such as protein folding and unfolding under applied force. PMID:16032901

  19. Radiation pressure excitation of Low Temperature Atomic Force & Magnetic Force Microscope (LT-AFM/MFM) for Imaging

    NASA Astrophysics Data System (ADS)

    Karci, Ozgur; Celik, Umit; Oral, Ahmet; NanoMagnetics Instruments Ltd. Team; Middle East Tech Univ Team

    2015-03-01

    We describe a novel method for excitation of Atomic Force Microscope (AFM) cantilevers by means of radiation pressure for imaging in an AFM for the first time. Piezo excitation is the most common method for cantilever excitation, but it may cause spurious resonance peaks. A fiber optic interferometer with 1310 nm laser was used both to measure the deflection of cantilever and apply a force to the cantilever in a LT-AFM/MFM from NanoMagnetics Instruments. The laser power was modulated at the cantilever`s resonance frequency by a digital Phase Lock Loop (PLL). The force exerted by the radiation pressure on a perfectly reflecting surface by a laser beam of power P is F = 2P/c. We typically modulate the laser beam by ~ 800 μW and obtain 10nm oscillation amplitude with Q ~ 8,000 at 2.5x10-4 mbar. The cantilever's stiffness can be accurately calibrated by using the radiation pressure. We have demonstrated performance of the radiation pressure excitation in AFM/MFM by imaging a hard disk sample between 4-300K and Abrikosov vortex lattice in BSCCO single crystal at 4K to for the first time.

  20. The elastic, electronic and magnetism structure of the MAl and M3Al (M=Fe and Ni) alloy with and without hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A.

    2016-03-01

    The energetic stability, electronic and magnetism of the MAl, M3Al alloy (M=Fe, Ni) and variant surfaces of MAl (001) with and without hydrogen atoms are investigated by utilizing DFT and GGA as the exchange-correlation potential. All presented alloys with and without the H atom absorption is found elastically and thermodynamically stable. The calculated absorption energy shows that H is more energetically stable in the bridge and octahedral site in MAl and M3Al alloys, respectively. Hydrogen atoms absorption is expanded and brittle the studied host alloys. The ability of absorption of H atom at more than one site in the MAl alloy is found energetically and thermodynamically stable. The H adsorption on the variant surfaces of MAl (001) is predicted too. Fourfold and top sites are found more energetically stable to adsorbed the H atom on the above surface layer of H/MAl-M and H/MAl-Al, respectively. The obvious changes are observed in the interlayer spacing for studied surfaces which yields to decrease the LDOS and magnetic moments of the surface and subsurface layers.

  1. Two Keggin-type heteropolytungstates with transition metal as a central atom: Crystal structure and magnetic study with 2D-IR correlation spectroscopy

    SciTech Connect

    Chai, Feng; Chen, YiPing; You, ZhuChai; Xia, ZeMin; Ge, SuZhi; Sun, YanQiong; Huang, BiHua

    2013-06-01

    Two Keggin-type heteropolytungstates, [Co(phen)₃]₃[CoW₁₂O₄₀]·9H₂O 1 (phen=1,10-phenanthroline) and [Fe(phen)₃]₂[FeW₁₂O₄₀]·H₃O·H₂O 2, have been synthesized via the hydrothermal technique and characterized by single crystal X-ray diffraction analyses, IR, XPS, TG analysis, UV–DRS, XRD, thermal-dependent and magnetic-dependent 2D-COS IR (two-dimensional infrared correlation spectroscopy). Crystal structure analysis reveals that the polyanions in compound 1 are linked into 3D supramolecule through hydrogen bonding interactions between lattice water molecules and terminal oxygen atoms of polyanion units, and [Co(phen)₃]²⁺ cations distributed in the polyanion framework with many hydrogen bonding interactions. The XPS spectra indicate that all the Co atoms in 1 are +2 oxidation state, the Fe atoms in 2 existing with +2 and +3 mixed oxidation states. - Graphical abstract: The magnetic-dependent synchronous 2D correlation IR spectra of 1 (a), 2 (b) over 0–50 mT in the range of 600–1000 cm⁻¹, the obvious response indicate two Keggin polyanions skeleton susceptible to applied magnetic field. Highlights: • Two Keggin-type heteropolytungstates with transition metal as a central atom has been obtained. • Compound 1 forms into 3D supramolecular architecture through hydrogen bonding between water molecules and polyanions. • Magnetic-dependent 2D-IR correlation spectroscopy was introduced to discuss the magnetism of polyoxometalate.

  2. Magnetic ordering and exchange interactions in structural modifications of M n3Ga alloys: Interplay of frustration, atomic order, and off-stoichiometry

    NASA Astrophysics Data System (ADS)

    Khmelevskyi, Sergii; Ruban, Andrei V.; Mohn, Peter

    2016-05-01

    Mn-Ga alloys close to the M n3Ga stoichiometry can be synthesized in three different crystal modifications: hexagonal, tetragonal, and face-centered cubic, both in bulk and in thin-film forms. The magnetic ordering of these modifications is varying from noncollinear antiferromagnetic in the hexagonal case to ferrimagnetic order in the tetragonal one, whereas it is still unknown for the atomically disordered fcc structure. Here we study the onset of magnetic order at finite temperatures in these systems on a first-principles basis calculating the interatomic magnetic exchange interactions in the high-temperature paramagnetic regime. We employ the disordered local moment formalism and the magnetic force theorem within the framework of the local spin-density approximation and Monte Carlo simulations taking also the effects of atomic disorder in fcc alloys into account. In particular we find the origin of the stabilization of the noncollinear 3 k structure in competition between antiferromagnetic inter- and in-plane couplings of frustrated kagome planes in hexagonal M n3Ga and predict the antiferromagnetic-1 collinear order due to frustration in fcc alloys. Special attention is paid to the effects of the off-stoichiometry and the consequences of atomic disorder. We calculate the site-preference energy of Ga antisite atoms in the tetragonal structures in the range of the compositions from M n3Ga to M n2Ga and slightly beyond and confirm the earlier explanation of the effect of magnetization increase due to Ga preferentially occupying one of the Mn sites.

  3. First principle study of magnetic and electronic properties of single X (X = Al, Si) atom added to small carbon clusters (C n X, n = 2-10)

    NASA Astrophysics Data System (ADS)

    Afshar, M.; Hoseini, S. S.; Sargolzaei, M.

    2016-07-01

    In this paper, the magnetic and electronic properties of single aluminum and silicon atom added to small carbon clusters (C n X; X = Al, Si; n = 2-10) are studied in the framework of generalized-gradient approximation using density functional theory. The calculations were performed for linear, two dimensional and three dimensional clusters based on full-potential local-orbital (FPLO) method. The total energies, HOMO-LUMO energy gap and total magnetic moments of the most stable structures are presented in this work. The calculations show that C n Si clusters have more stability compared to C n Al clusters. In addition, our magnetic calculations were shown that the C n Al isomers are magnetic objects whereas C n Si clusters are nonmagnetic objects.

  4. Atomic-level Pseudo-degeneracy of Atomic Levels Giving Transitions Induced by Magnetic Fields, of Importance for Determining the Field Strengths in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Li, Wenxian; Yang, Yang; Tu, Bingsheng; Xiao, Jun; Grumer, Jon; Brage, Tomas; Watanabe, Tetsuya; Hutton, Roger; Zou, Yaming

    2016-08-01

    We present a measured value for the degree of pseudo-degeneracy between two fine-structure levels in Fe9+ from line intensity ratios involving a transition induced by an external magnetic field. The extracted fine-structure energy difference between the 3{p}43d{}4{D}5/2 and {}4{D}7/2 levels, where the latter is the upper state for the magnetic-field induced line, is needed in our recently proposed method to measure magnetic-field strengths in the solar corona. The intensity of the 3{p}43d{}4{D}7/2\\to 3{p}5{}2{P}3/2 line at 257.262 Å is sensitive to the magnetic field external to the ion. This sensitivity is in turn strongly dependent on the energy separation in the pseudo-degeneracy through the mixing induced by the external magnetic field. Our measurement, which uses an Electron Beam Ion Trap with a known magnetic-field strength, indicates that this energy difference is 3.5 cm‑1. The high abundance of Fe9+ and the sensitivity of the line’s transition probability to field strengths below 0.1 T opens up the possibility of diagnosing coronal magnetic fields. We propose a new method to measure the magnetic field in the solar corona, from similar intensity ratios in Fe9+. In addition, the proposed method to use the line ratio of the blended line 3{p}43d{}4{D}7/{2,5/2}\\to 3{p}5{}2{P}3/2 with another line from Fe x as the density diagnostic should evaluate the effect of the magnetic-field-induced transition line.

  5. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  6. [Connection of magnetic antisense probe with SK-Br-3 oncocyte mRNA nucleotide detected by high resolution atomic force microscope].

    PubMed

    Tan, Shude; Ouyang, Yu; Li, Xinyou; Wen, Ming; Li, Shaolin

    2011-06-01

    The present paper is aimed to detect superparamagnetic iron oxide labeled c-erbB2 oncogene antisense oligonucleotide probe (magnetic antisense probe) connected with SK-Br-3 oncocyte mRNA nucleotide by high resolution atomic force microscope (AFM). We transfected SK-Br-3 oncocyte with magnetic antisense probe, then observed the cells by AFM with high resolution and detected protein expression and magnetic resonance imagine (MRI). The high resolution AFM clearly showed the connection of the oligonucleotide remote end of magnetic antisense probe with the mRNA nucleotide of oncocyte. The expression of e-erbB2 protein in SK-Br3 cells were highly inhibited by using magnetic antisense probe. We then obtained the lowest signal to noise ratio (SNR) of SK-Br-3 oncocyte transfected with magnetic antisense probe by MRI (P<0.05). These experiments demonstrated that the high resolution AFM could be used to show the binding of magnetic antisense probe and SK-Br-3 mRNA of tumor cell nuclear. PMID:21774198

  7. Atomic sulfur: Frequency measurement of the J = 0 left arrow 1 fine-structure transition at 56.3 microns by laser magnetic resonance

    NASA Technical Reports Server (NTRS)

    Brown, John M.; Evenson, Kenneth M.; Zink, Lyndon R.

    1994-01-01

    The J = 0 left arrow 1 fine-structure transition in atomic sulfur (S I) in its ground (3)P state has been detected in the laboratory by far-infrared laser magnetic resonance. The fine-structure interval has been measured accurately as 5,322,492.9 +/- 2.8 MHz which corresponds to a wavelength of 56.325572 +/- 0.000030 micrometers.

  8. Elimination of interface states of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction by inserting an Al atomic layer

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Yang, G. W.

    2011-01-01

    Aiming at improvement performance of Co2MnSi/MgO/Co2MnSi magnetic tunneling junction (MTJ), we have studied interface behaviors of Co2MnSi/MgO by inserting an Al atomic layer between Heusler alloy and barrier, i.e., CoCo/Al/O, MnSi/Al/O, MnMn/Al/O and SiSi/Al/O four interfaces. It was found that CoCo/Al/O is stable and half-metallic, meaning interface states can be eliminated in this system. Hybridization and repulsion of transition-metal d and p states of sp atoms at interface and electrons transfer between interfacial atoms were suggested to be responsible for interface states elimination. These findings open a way to eliminate the interface states in MTJ.

  9. Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}.

    PubMed

    Altmeyer, Michaela; Jeschke, Harald O; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F; Rozenberg, Marcelo J; Valentí, Roser; Gabay, Marc

    2016-04-15

    Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100  meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface. PMID:27127984

  10. Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO3

    NASA Astrophysics Data System (ADS)

    Altmeyer, Michaela; Jeschke, Harald O.; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F.; Rozenberg, Marcelo J.; Valentí, Roser; Gabay, Marc

    2016-04-01

    Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO3, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ˜100 meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t2 g itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.

  11. Structure, electronic and magnetic properties of hexagonal boron nitride sheets doped by 5d transition metal atoms: First-principles calculations and molecular orbital analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaofu; Geng, Zhaohui; Cai, Danyun; Pan, Tongxi; Chen, Yixin; Dong, Liyuan; Zhou, Tiege

    2015-01-01

    A first-principles calculation based on density functional theory is carried out to reveal the geometry, electronic structures and magnetic properties of hexagonal boron nitride sheets (h-BNSs) doped by 5d transitional mental atoms (Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg) at boron-site (B5d) and nitrogen-site (N5d). Results of pure h-BNS, h-BNS with B vacancy (VB) and N vacancy (VN) are also given for comparison. It is shown that all the h-BNSs doped with 5d atoms possess a C3v local symmetry except for NLu and NHg which have a clear deviation. For the same 5d dopant, the binding energy of B5d is larger than that of N5d, which indicates the substitution of a 5d atom for B is preferred. The total densities of states are presented, where impurity energy levels exist. Besides, the total magnetic moments (TMMs) change regularly with the increment of the 5d atomic number. Theoretical analyses by molecular orbital under C3v symmetry explain the impurity energy levels and TMMs.

  12. Neutral atom traps.

    SciTech Connect

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  13. Newton's Atom

    NASA Astrophysics Data System (ADS)

    Chaney, Andrea; Espinosa, James; Espinosa, James

    2006-10-01

    At the turn of the twentieth century, physicists and chemists were developing atomic models. Some of the phenomena that they had to explain were the periodic table, the stability of the atom, and the emission spectra. Niels Bohr is known as making the first modern picture that accounted for these. Unknown to much of the physics community is the work of Walter Ritz. His model explained more emission spectra and predates Bohr's work. We will fit several spectra using Ritz's magnetic model for the atom. The problems of stability and chemical periodicity will be shown to be challenges that this model has difficulty solving, but we will present some potentially useful adaptations to the Ritzian atom that can account for them.

  14. Warm-Up Activities.

    ERIC Educational Resources Information Center

    Mingguang, Yang

    1999-01-01

    Discusses how warm-up activities can help to make the English-as-a-foreign-language classroom a lively and interesting place. Warm-up activities are games carried out at the beginning of each class to motivate students to make good use of class time. (Author/VWL)

  15. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: an ab initio study of He + CH2(X) collisions.

    PubMed

    Tscherbul, T V; Grinev, T A; Yu, H-G; Dalgarno, A; Kłos, Jacek; Ma, Lifang; Alexander, Millard H

    2012-09-14

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH(2)(X(3)B(1))] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH(2)(X(3)B(1)) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH(2), CHD, and CD(2) molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH(2)(X(3)B(1)) molecules in a magnetic trap. Furthermore, we find that ortho-CH(2) undergoes collision-induced spin relaxation much more slowly than para-CH(2), which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules. PMID:22979854

  16. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X~) collisions

    NASA Astrophysics Data System (ADS)

    Tscherbul, T. V.; Grinev, T. A.; Yu, H.-G.; Dalgarno, A.; Kłos, Jacek; Ma, Lifang; Alexander, Millard H.

    2012-09-01

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH_2(tilde{X}^3B_1)] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH_2(tilde{X}^3B_1) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH2, CHD, and CD2 molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH_2(tilde{X}^3B_1) molecules in a magnetic trap. Furthermore, we find that ortho-CH2 undergoes collision-induced spin relaxation much more slowly than para-CH2, which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules.

  17. Investigation of the magnetic dipole field at the atomic scale in quasi-one-dimensional paramagnetic conductor Li0.9Mo6O17.

    PubMed

    Wu, Guoqing; Ye, Xiao-shan; Zeng, Xianghua; Wu, Bing; Clark, W G

    2016-01-13

    We report magnetic dipole field investigation at the atomic scale in a single crystal of quasi-one-dimensional (Q1D) paramagnetic conductor Li0.9Mo6O17, using a paramagnetic electron model and (7)Li-NMR spectroscopy measurements with an externally applied magnetic field B 0  =  9 T. We find that the magnetic dipole field component ([Formula: see text]) parallel to B 0 at the Li site from the Mo electrons has no lattice axial symmetry; it is small around the middle between the lattice a and c axes in the ac-plane with the minimum at the field orientation angle [Formula: see text], while the [Formula: see text] maximum is at [Formula: see text] when B 0 is applied perpendicular to b ([Formula: see text]), where [Formula: see text] represents the direction of [Formula: see text]. Further estimation indicates that [Formula: see text] has a maximum value of 0.35 G at B 0  =  9 T. By minimizing the potential magnetic contributions to the NMR spectra satellites with the NMR spectroscopy measurements at the direction where the value of the magnetic dipole field component [Formula: see text] is  ∼0, the behavior of the electron charge statics is exhibited. This work demonstrates that the magnetic dipole field of the Mo electrons is the dominant source of the local magnetic fields at the Li site, and suggests that the unknown metal-'insulator' crossover at low temperatures is not a charge effect. The work also reveals valuable local electric and magnetic field information for further NMR investigation as recently suggested (2012 Phys. Rev. B 85 235128) regarding the unusual properties of the material. PMID:26571041

  18. Effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La(Fe, Si)13-based compounds

    NASA Astrophysics Data System (ADS)

    Zhang, Hu; Hu, FengXia; Sun, JiRong; Shen, BaoGen

    2013-12-01

    La(Fe, Si)13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La(Fe, Si)13 compounds. By introducing H and/or C atoms, the Curie temperature T C increases notably with the increase of lattice expansion which makes the Fe 3 d band narrow and reduces the overlap of the Fe 3 d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduction of interstitial C atoms promotes the formation of NaZn13-type (1:13) phase in La(Fe, Si)13 compounds, and thus reducing the annealing time significantly from 40 days for LaFe11.7Si1.3 to a week for LaFe11.7Si1.3C0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La(Fe, Si)13 compounds around room temperature, for instance, La0.7Pr0.3Fe11.5Si1.5C0.2H1.2 exhibits a large |Δ S M| of 22.1 J/(kg·K) at T C = 321 K without hysteresis loss for a field change of 0-5 T.

  19. FAST TRACK COMMUNICATION: Generalized geometrical model for photoionization of polarized atoms: II. Magnetic dichroism in the 3p photoemission from the K 3p64s 2S1/2 ground state

    NASA Astrophysics Data System (ADS)

    Grum-Grzhimailo, A. N.; Cubaynes, D.; Heinecke, E.; Hoffmann, P.; Zimmermann, P.; Meyer, M.

    2010-10-01

    The generalized geometrical model for photoionization from polarized atoms is extended to include mixing of configurations in the initial atomic and/or the final photoion states. The theoretical results for angle-resolved linear and circular magnetic dichroism are in good agreement with new high-resolution photoelectron data for 3p-1 photoionization of potassium atoms polarized in the K 3p64s 2S1/2 ground state by laser optical pumping.

  20. A fast parallel code for calculating energies and oscillator strengths of many-electron atoms at neutron star magnetic field strengths in adiabatic approximation

    NASA Astrophysics Data System (ADS)

    Engel, D.; Klews, M.; Wunner, G.

    2009-02-01

    We have developed a new method for the fast computation of wavelengths and oscillator strengths for medium-Z atoms and ions, up to iron, at neutron star magnetic field strengths. The method is a parallelized Hartree-Fock approach in adiabatic approximation based on finite-element and B-spline techniques. It turns out that typically 15-20 finite elements are sufficient to calculate energies to within a relative accuracy of 10-5 in 4 or 5 iteration steps using B-splines of 6th order, with parallelization speed-ups of 20 on a 26-processor machine. Results have been obtained for the energies of the ground states and excited levels and for the transition strengths of astrophysically relevant atoms and ions in the range Z=2…26 in different ionization stages. Catalogue identifier: AECC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3845 No. of bytes in distributed program, including test data, etc.: 27 989 Distribution format: tar.gz Programming language: MPI/Fortran 95 and Python Computer: Cluster of 1-26 HP Compaq dc5750 Operating system: Fedora 7 Has the code been vectorised or parallelized?: Yes RAM: 1 GByte Classification: 2.1 External routines: MPI/GFortran, LAPACK, PyLab/Matplotlib Nature of problem: Calculations of synthetic spectra [1] of strongly magnetized neutron stars are bedevilled by the lack of data for atoms in intense magnetic fields. While the behaviour of hydrogen and helium has been investigated in detail (see, e.g., [2]), complete and reliable data for heavier elements, in particular iron, are still missing. Since neutron stars are formed by the collapse of the iron cores of massive stars, it may be assumed that their atmospheres contain an iron plasma. Our objective is to fill the gap

  1. Role of magnetic and atomic ordering in the martensitic transformation of Ni-Mn-In from a first-principles study

    NASA Astrophysics Data System (ADS)

    Li, Chun-Mei; Luo, Hu-Bin; Hu, Qing-Miao; Yang, Rui; Johansson, Börje; Vitos, Levente

    2012-12-01

    The composition-dependent lattice parameters, crystal structure, elastic properties, magnetic moment, and electronic structure of Ni2Mn1+xIn1-x (0≤x≤0.6) are studied by using first-principles calculations. It is shown that the martensitic phase transition (MPT) from cubic L21 to tetragonal L10 accompanies the MnMn-MnIn ferromagnetic (FM) to antiferromagnetic (AFM) transition, at around the critical composition x=0.32, in agreement with the experimental measurement. The Mn-In atomic disorder leads to decreasing stability of the martensite relative to the austenite, which depresses the MPT. The shear elastic constant C' of the parent phase first decreases slightly with increasing x and then remains almost unchanged above x=0.32, indicating C' alone cannot account for the increase of the MPT temperature with x. The total magnetic moments for the L21 phase are in good agreement with those determined by experiments, whereas for the L10 phase they are slightly larger than the experimental data due to the possible Mn-In atomic disorder in the sample. The calculated density of states demonstrate that the covalent bonding between the minority spin states of Ni and In plays an important role in both the magnetic and structural stability.

  2. Observation of acoustic-phonon-like mode driven by magnetic imbalance between neighboring Fe atoms in Fe1+yTe (y < 0 . 12)

    NASA Astrophysics Data System (ADS)

    Fobes, David; Zaliznyak, Igor; Xu, Zhijun; Gu, Genda; Tranquada, John M.; He, Xu-Gang; Ku, Wei; Garlea, Ovidiu

    2014-03-01

    We have studied the evolution with temperature of the low-energy inelastic spectra of Fe1+yTe (y < 0 . 12), a parent compound of the iron-chalcogenide superconductor family, revealing an acoustic mode at an unexpected position. Recently, we found evidence for the formation of a bond-order wave leading to ferro-orbital order in the monoclinic phase, in part due to the observation of an elastic structural peak at (100) in the low-temperature monoclinic phase [D. Fobes, et al., arXiv:1307.7162]. In the inelastic spectra we observe a sharp acoustic-phonon-like mode dispersing out of the (100) position in the monoclinic phase. Surprisingly, the mode survives in the tetragonal phase, despite the absence of a Bragg peak at (100); such a peak is forbidden by symmetry. LDA calculations suggest this mode could involve significant magnetic scattering. By assuming in-phase virtual displacement of the Fe atoms from their equilibrium position in a frozen phonon calculation, we have found a small but significant imbalance in the magnetic moments between the two Fe atoms within the unit cell, suggesting magnetic contribution to the mode. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC02-98CH10886. Research conducted at ORNL Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US DOE.

  3. Analytic models of warm plasma dispersion relations

    SciTech Connect

    Seough, J. J.; Yoon, P. H.

    2009-09-15

    The present paper is concerned with analytic models of warm plasma dispersion relations for electromagnetic waves propagating parallel to the ambient magnetic field. Specifically, effects of finite betas on two slow modes, namely, the left-hand circularly polarized ion-cyclotron mode and the right-hand circularly polarized whistler mode, are investigated. Analytic models of the warm plasma dispersion relations are constructed on the basis of conjecture and upon comparisons with numerically found roots. It is shown that the model solutions are good substitutes for actual roots. The significance of the present work in the context of nonlinear plasma research is discussed.

  4. Warm and Cool Dinosaurs.

    ERIC Educational Resources Information Center

    Mannlein, Sally

    2001-01-01

    Presents an art activity in which first grade students draw dinosaurs in order to learn about the concept of warm and cool colors. Explains how the activity also helped the students learn about the concept of distance when drawing. (CMK)

  5. Global warming elucidated

    SciTech Connect

    Shen, S.

    1995-03-01

    The meaning of global warming and its relevance to everyday life is explained. Simple thermodynamics is used to predict an oscillatory nature of the change in climate due to global warming. Global warming causes extreme events and bad weather in the near term. In the long term it may cause the earth to transition to another equilibrium state through many oscillation in climatic patterns. The magnitudes of these oscillations could easily exceed the difference between the end points. The author further explains why many no longer fully understands the nature and magnitudes of common phenomena such as storms and wind speeds because of these oscillations, and the absorptive properties of clouds. The author links the increase in duration of the El Nino to global warming, and further predicts public health risks as the earth transitions to another equilibrium state in its young history.

  6. Reconciling Warming Trends

    NASA Technical Reports Server (NTRS)

    Schmidt, Gavin A.; Shindell, Drew T.; Tsigaridis, Konstantinos

    2014-01-01

    Climate models projected stronger warming over the past 15 years than has been seen in observations. Conspiring factors of errors in volcanic and solar inputs, representations of aerosols, and El NiNo evolution, may explain most of the discrepancy.

  7. Existence and stability of alternative ion-acoustic solitary wave solution of the combined MKdV-KdV-ZK equation in a magnetized nonthermal plasma consisting of warm adiabatic ions

    SciTech Connect

    Das, Jayasree; Bandyopadhyay, Anup; Das, K. P.

    2007-09-15

    The purpose of this paper is to present the recent work of Das et al. [J. Plasma Phys. 72, 587 (2006)] on the existence and stability of the alternative solitary wave solution of fixed width of the combined MKdV-KdV-ZK (Modified Korteweg-de Vries-Korteweg-de Vries-Zakharov-Kuznetsov) equation for the ion-acoustic wave in a magnetized nonthermal plasma consisting of warm adiabatic ions in a more generalized form. Here we derive the alternative solitary wave solution of variable width instead of fixed width of the combined MKdV-KdV-ZK equation along with the condition for its existence and find that this solution assumes the sech profile of the MKdV-ZK (Modified Korteweg-de Vries-Zakharov-Kuznetsov) equation, when the coefficient of the nonlinear term of the KdV-ZK (Korteweg-de Vries-Zakharov-Kuznetsov) equation tends to zero. The three-dimensional stability analysis of the alternative solitary wave solution of variable width of the combined MKdV-KdV-ZK equation shows that the instability condition and the first order growth rate of instability are exactly the same as those of the solitary wave solution (the sech profile) of the MKdV-ZK equation, when the coefficient of the nonlinear term of the KdV-ZK equation tends to zero.

  8. Variational calculation of ground-state energy of iron atoms and condensed matter in strong magnetic fields. [at neutron star surfaces

    NASA Technical Reports Server (NTRS)

    Flowers, E. G.; Ruderman, M. A.; Lee, J.-F.; Sutherland, P. G.; Hillebrandt, W.; Mueller, E.

    1977-01-01

    Variational calculations of the binding energies of iron atoms and condensed matter in strong magnetic fields (greater than 10 to the 12th gauss). These calculations include the electron exchange energy. The cohesive energy of the condensed matter, which is the difference between these two binding energies, is of interest in pulsar theories and in the description of the surfaces of neutron stars. It is found that the cohesive energy ranges from 2.6 keV to 8.0 keV.

  9. Optimization of Doppler-free magnetically induced dichroic locking spectroscopy on the 1S0-3P1 transition of a neutral mercury atom

    NASA Astrophysics Data System (ADS)

    Liu, Hongli; Yin, Shiqi; Qian, Jun; Xu, Zhen; Wang, Yuzhu

    2013-04-01

    Doppler-free dichroic locking (DFDL) spectroscopy on the 1S0-3P1 transition of neutral mercury (Hg) atoms is observed in a 5 mm long vapour cell. The performance of the DFDL signal, such as its slope and amplitude, is investigated in detail. The optimal axial magnetic field and cell temperature (optical depth) for the observed seven transitions are also highlighted. We also demonstrate an important application of DFDL spectroscopy in the frequency stabilization of an ultraviolet laser on the transition of 200Hg.

  10. Inhomogeneous broadening of optically detected magnetic resonance of the ensembles of nitrogen-vacancy centers in diamond by interstitial carbon atoms

    SciTech Connect

    Levchenko, A. O. Vasil'ev, V. V.; Zibrov, S. A.; Zibrov, A. S.; Sivak, A. V.; Fedotov, I. V.

    2015-03-09

    We study the impact of the negatively charged nitrogen-vacancy (NV{sup –}) center density on the lattice strain resulting in the splitting of the optically detected magnetic resonance of HPHT diamond. A simple model, taking into account the presence of the interstitial carbon atoms, acting like a wedge force on the crystal lattice, explains the broadening and splitting of the optically detected magnetic resonance of the ensemble of NV{sup –} centers at densities within the range of 10{sup 13} ÷ 10{sup 14 }cm{sup −3}. This model uses a complete generalized spin Hamiltonian, takes into account the strain-effect of each center in the ensemble and gives good agreement with experimental data.

  11. Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction

    NASA Astrophysics Data System (ADS)

    Espejo, A. P.; Zierold, R.; Gooth, J.; Dendooven, J.; Detavernier, C.; Escrig, J.; Nielsch, K.

    2016-08-01

    Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1‑x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

  12. Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction.

    PubMed

    Espejo, A P; Zierold, R; Gooth, J; Dendooven, J; Detavernier, C; Escrig, J; Nielsch, K

    2016-08-26

    Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated. PMID:27454574

  13. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1993-07-20

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  14. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1992-06-30

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  15. Long range global warming

    SciTech Connect

    Rolle, K.C.; Pulkrabek, W.W.; Fiedler, R.A.

    1995-12-31

    This paper explores one of the causes of global warming that is often overlooked, the direct heating of the environment by engineering systems. Most research and studies of global warming concentrate on the modification that is occurring to atmospheric air as a result of pollution gases being added by various systems; i.e., refrigerants, nitrogen oxides, ozone, hydrocarbons, halon, and others. This modification affects the thermal radiation balance between earth, sun and space, resulting in a decrease of radiation outflow and a slow rise in the earth`s steady state temperature. For this reason the solution to the problem is perceived as one of cleaning up the processes and effluents that are discharged into the environment. In this paper arguments are presented that suggest, that there is a far more serious cause for global warming that will manifest itself in the next two or three centuries; direct heating from the exponential growth of energy usage by humankind. Because this is a minor contributor to the global warming problem at present, it is overlooked or ignored. Energy use from the combustion of fuels and from the output of nuclear reactions eventually is manifest as warming of the surroundings. Thus, as energy is used at an ever increasing rate the consequent global warming also increases at an ever increasing rate. Eventually this rate will become equal to a few percent of solar radiation. When this happens the earth`s temperature will have risen by several degrees with catastrophic results. The trends in world energy use are reviewed and some mathematical models are presented to suggest future scenarios. These models can be used to predict when the global warming problem will become undeniably apparent, when it will become critical, and when it will become catastrophic.

  16. Warm up to the idea: Global warming is here

    SciTech Connect

    Lynch, C.F.

    1996-07-01

    This article summarizes recent information about global warming as well as the history of greenhouse gas emissions which have lead to more and more evidence of global warming. The primary source detailed is the second major study report on global warming by the Intergovernmental Panel on climate change. Along with comments about the environmental effects of global warming such as coastline submersion, the economic, social and political aspects of alleviating greenhouse emissions and the threat of global warming are discussed.

  17. Magnetism of randomly distributed f atoms in (U{sub 1{minus}x}Nd{sub x})Co{sub 2}Ge{sub 2} solid solutions

    SciTech Connect

    Caspi, E. |; Kuznietz, M.; Ettedgui, H.; Pinto, H.; Melamud, M.; Shaked, H.

    1998-01-01

    Solid solutions of the (U{sub 1{minus}x}Nd{sub x})Co{sub 2}Ge{sub 2} system (x=0.25, 0.50, 0.75) are found by neutron diffraction to have tetragonal ThCr{sub 2}Si{sub 2}-type crystal structure (space group I4/mmm), same as their end compounds (x =0, 1). In the solid solutions, U and Nd atoms are randomly distributed in the basal planes. The end compounds and the solid solutions are paramagnetic at room temperature. At 12 K the (U,Nd) sublattice has the antiferromagnetic AF-I magnetic structure [+{minus}+{minus} stacking of ferromagnetic (U,Nd) planes along c], with moments parallel to the c axis. It is found that within a ferromagnetic basal plane the U magnetic moments are parallel to the Nd magnetic moments, unlike (U,Tb), where they are antiparallel. This shows that the {open_quotes}spin charge{close_quotes} rule for lanthanides extends to U-lanthanide systems. Neutron-diffraction and ac-susceptibility results are compared in order to investigate the character of the magnetic transition in the solid solutions. {copyright} {ital 1998} {ital The American Physical Society}

  18. Preparation of a magnetic molecularly imprinted polymer by atom-transfer radical polymerization for the extraction of parabens from fruit juices.

    PubMed

    You, Xiaoxiao; Piao, Chungying; Chen, Ligang

    2016-07-01

    A silica-based surface magnetic molecularly imprinted polymer for the selective recognition of parabens was prepared using a facile and general method that combined atom-transfer radical polymerization with surface imprinting technique. The prepared magnetic molecularly imprinted polymer was characterized by transmission electron microscopy, Fourier transform infrared spectrometry and physical property measurement. The isothermal adsorption experiment and kinetics adsorption experiment investigated the adsorption property of magnetic molecularly imprinted polymer to template molecule. The four parabens including methylparaben, ethylparaben, propylparaben, and butylparaben were used to assess the rebinding selectivity. An extraction method, which used magnetic molecularly imprinted polymer as adsorbents coupled with high-performance liquid chromatography for the determination of the four parabens in fruit juice samples was developed. Under the optimal conditions, the limits of detections of the four parabens were 0.028, 0.026, 0.021, and 0.026 mg/L, respectively. The precision expressed as relative standard deviation ranging from 2.6 to 8.9% was obtained. In all three fortified levels, recoveries of parabens were in the range of 72.5-89.4%. The proposed method has been applied to different fruit juice samples including orange juice, grape juice, apple juice and peach juice, and satisfactory results were obtained. PMID:27214157

  19. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics

    NASA Astrophysics Data System (ADS)

    McKay Parry, Nicholas; Baker, Mark; Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina

    2014-08-01

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ˜5 mm-1 and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW.

  20. Atomic magnetometer

    DOEpatents

    Schwindt, Peter; Johnson, Cort N.

    2012-07-03

    An atomic magnetometer is disclosed which uses a pump light beam at a D1 or D2 transition of an alkali metal vapor to magnetically polarize the vapor in a heated cell, and a probe light beam at a different D2 or D1 transition to sense the magnetic field via a polarization rotation of the probe light beam. The pump and probe light beams are both directed along substantially the same optical path through an optical waveplate and through the heated cell to an optical filter which blocks the pump light beam while transmitting the probe light beam to one or more photodetectors which generate electrical signals to sense the magnetic field. The optical waveplate functions as a quarter waveplate to circularly polarize the pump light beam, and as a half waveplate to maintain the probe light beam linearly polarized.

  1. Relativistic effects on the nuclear magnetic shieldings of rare-gas atoms and halogen in hydrogen halides within relativistic polarization propagator theory

    NASA Astrophysics Data System (ADS)

    Gomez, Sergio S.; Maldonado, Alejandro; Aucar, Gustavo A.

    2005-12-01

    In this work an analysis of the electronic origin of relativistic effects on the isotropic dia- and paramagnetic contributions to the nuclear magnetic shielding σ(X ) for noble gases and heavy atoms of hydrogen halides is presented. All results were obtained within the 4-component polarization propagator formalism at different level of approach [random-phase approximation (RPA) and pure zeroth-order approximation (PZOA)], by using a local version of the DIRAC code. From the fact that calculations of diamagnetic contributions to σ within RPA and PZOA approaches for HX(X =Br,I,At) and rare-gas atoms are quite close each to other and the finding that the diamagnetic part of the principal propagator at the PZOA level can be developed as a series [S(Δ)], it was found that there is a branch of negative-energy "virtual" excitations that contribute with more than 98% of the total diamagnetic value even for the heavier elements, namely, Xe, Rn, I, and At. It contains virtual negative-energy molecular-orbital states with energies between -2mc2 and -4mc2. This fact can explain the excellent performance of the linear response elimination of small component (LR-ESC) scheme for elements up to the fifth row in the Periodic Table. An analysis of the convergency of S(Δ ) and its physical implications is given. It is also shown that the total contribution to relativistic effects of the innermost orbital (1s1/2) is by far the largest. For the paramagnetic contributions results at the RPA and PZOA approximations are similar only for rare-gas atoms. On the other hand, if the mass-correction contributions to σp are expressed in terms of atomic orbitals, a different pattern is found for 1s1/2 orbital contributions compared with all other s-type orbitals when the whole set of rare-gas atoms is considered.

  2. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    NASA Astrophysics Data System (ADS)

    Liu, X. H.; Luo, H.; Qu, T. L.; Yang, K. Y.; Ding, Z. C.

    2015-10-01

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  3. Observation of the Forbidden Magnetic Dipole Transition 6{sup 2}P{sub ½} --> 7{sup 2}P{sub ½} in Atomic Thallium

    DOE R&D Accomplishments Database

    Chu, S.

    1976-10-01

    A measurement of the 6{sup 2}P{sub ½} --> 7{sup 2}P{sub ½} forbidden magnetic dipole matrix element in atomic thallium is described. A pulsed, linearly polarized dye laser tuned to the transition frequency is used to excite the thallium vapor from the 6{sup 2}P{sub ½} ground state to the 7{sup 2}P{sub ½} excited state. Interference between the magnetic dipole M1 amplitude and a static electric field induced E1 amplitude results in an atomic polarization of the 7{sup 2}P{sub ½} state, and the subsequent circular polarization of 535 nm fluorescence. The circular polarization is seen to be proportional to / as expected, and measured for several transitions between hyperfine levels of the 6{sup 2}P{sub ½} and 7{sup 2}P{sub ½} states. The result is = -(2.11 +- 0.30) x 10{sup -5} parallel bar e parallel bar dirac constant/2mc, in agreement with theory.

  4. Recyclable decoration of amine-functionalized magnetic nanoparticles with Ni(2+) for determination of histidine by photochemical vapor generation atomic spectrometry.

    PubMed

    Hu, Yuan; Wang, Qi; Zheng, Chengbin; Wu, Li; Hou, Xiandeng; Lv, Yi

    2014-01-01

    It is critically important to accurately determine histidine since it is an indicator for many diseases when at an abnormal level. Here, an inexpensive and simple method using an amine-functionalized magnetic nanoparticle-based Ni(2+)-histidine affinity pair system was developed for highly sensitive and selective detection of histidine in human urine by photochemical vapor generation atomic spectrometry. Ni(2+) was first bound to the amine groups of the amine-functionalized magnetic nanoparticles and then liberated to solution via the highly specific interaction between the histidine and Ni(2+) in the presence of histidine. The liberated histidine-Ni(2+) complex was exposed to UV irradiation in the presence of formic acid to form gaseous nickel tetracarbonyl, which was separated from the sample matrix and determined by atomic absorption/fluorescence spectrometry. Compared to other methods, this approach promises high sensitivity, simplicity in design, and convenient operation. The need for organic solvents, enzymatic reactions, separation processes, chemical modification, expensive instrumentations, and sophisticated and complicated pretreatment is minimized with this strategy. A limit of detection of 1 nM was obtained and provided tens-to-hundreds of fold improvements over that achieved with conventional methods. The protocol was evaluated by analysis of several urine samples with good recoveries and showed great potential for practical application. PMID:24286112

  5. Coherent coupling of alkali atoms by random collisions.

    PubMed

    Katz, Or; Peleg, Or; Firstenberg, Ofer

    2015-09-11

    Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibrate the spin state of the atoms in the vapor. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali species to another species, mediated by these random collisions. We show that the minor species (potassium) inherits the magnetic properties of the dominant species (rubidium), including its lifetime (T_{1}), coherence time (T_{2}), gyromagnetic ratio, and spin-exchange relaxation-free magnetic-field threshold. We further show that this coupling can be completely controlled by varying the strength of the magnetic field. Finally, we explain these phenomena analytically by mode mixing of the two species via spin-exchange collisions. PMID:26406827

  6. Influence of ball milling on atomic structure and magnetic properties of Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} glassy alloy

    SciTech Connect

    Taghvaei, Amir Hossein; Stoica, Mihai; Bednarčik, Jozef; Kaban, Ivan; Shahabi, Hamed Shakur; Khoshkhoo, Mohsen Samadi; Janghorban, Kamal; Eckert, Jürgen

    2014-06-01

    The influence of ball milling on the atomic structure and magnetic properties of the Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} metallic glass with a high thermal stability and excellent soft magnetic properties has been investigated. After 14 h of milling, the obtained powders were found to consist mainly of an amorphous phase and a small fraction of the (Co,Fe){sub 21}Ta{sub 2}B{sub 6} nanocrystals. The changes in the reduced pair correlation functions suggest noticeable changes in the atomic structure of the amorphous upon ball milling. Furthermore, it has been shown that milling is accompanied by introduction of compressive and dilatational sites in the glassy phase and increasing the fluctuation of the atomic-level hydrostatic stress without affecting the coordination number of the nearest neighbors. Ball milling has decreased the thermal stability and significantly affected the magnetic properties through increasing the saturation magnetization, Curie temperature of the amorphous phase and coercivity. - Highlights: • Ball milling affected the atomic structure of Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} metallic glass. • Mechanically-induced crystallization started after 4 h milling. • Milling increased the fluctuation of the atomic-level hydrostatic stress in glass. • Ball milling influenced the thermal stability and magnetic properties.

  7. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics.

    PubMed

    McKay Parry, Nicholas; Baker, Mark; Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina

    2014-08-01

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ~5 mm(-1) and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW. PMID:25173328

  8. Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics

    SciTech Connect

    McKay Parry, Nicholas Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina; Baker, Mark

    2014-08-15

    We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ∼5 mm{sup −1} and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW.

  9. Warm and Cool Cityscapes

    ERIC Educational Resources Information Center

    Jubelirer, Shelly

    2012-01-01

    Painting cityscapes is a great way to teach first-grade students about warm and cool colors. Before the painting begins, the author and her class have an in-depth discussion about big cities and what types of buildings or structures that might be seen in them. They talk about large apartment and condo buildings, skyscrapers, art museums,…

  10. Identifying the Molecular Origin of Global Warming

    NASA Technical Reports Server (NTRS)

    Bera, Partha P.; Francisco, Joseph S.; Lee, Timothy J.

    2009-01-01

    We have investigated the physical characteristics of greenhouse gases (GHGs) to assess which properties are most important in determining the efficiency of a GHG. Chlorofluorcarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen fluorides, and various other known atmospheric trace molecules have been included in this study. Compounds containing the halogens F or Cl have in common very polar X-F or X-Cl bonds, particularly the X-F bonds. It is shown that as more F atoms bond to the same central atom, the bond dipoles become larger as a result of the central atom becoming more positive. This leads to a linear increase in the total or integrated XF bond dipole derivatives for the molecule, which leads to a non-linear (quadratic) increase in infrared (IR) intensity. Moreover, virtually all of the X-F bond stretches occur in the atmospheric IR window as opposed to X-H stretches, which do not occur in the atmospheric window. It is concluded that molecules possessing several F atoms will always have a large radiative forcing parameter in the calculation of their global warming potential. Some of the implications for global warming and climate change are discussed.

  11. -induced continental warming

    NASA Astrophysics Data System (ADS)

    Kamae, Youichi; Watanabe, Masahiro; Kimoto, Masahide; Shiogama, Hideo

    2014-11-01

    In this the second of a two-part study, we examine the physical mechanisms responsible for the increasing contrast of the land-sea surface air temperature (SAT) in summertime over the Far East, as observed in recent decades and revealed in future climate projections obtained from a series of transient warming and sensitivity experiments conducted under the umbrella of the Coupled Model Intercomparison Project phase 5. On a global perspective, a strengthening of land-sea SAT contrast in the transient warming simulations of coupled atmosphere-ocean general circulation models is attributed to an increase in sea surface temperature (SST). However, in boreal summer, the strengthened contrast over the Far East is reproduced only by increasing atmospheric CO2 concentration. In response to SST increase alone, the tropospheric warming over the interior of the mid- to high-latitude continents including Eurasia are weaker than those over the surrounding oceans, leading to a weakening of the land-sea SAT contrast over the Far East. Thus, the increasing contrast and associated change in atmospheric circulation over East Asia is explained by CO2-induced continental warming. The degree of strengthening of the land-sea SAT contrast varies in different transient warming scenarios, but is reproduced through a combination of the CO2-induced positive and SST-induced negative contributions to the land-sea contrast. These results imply that changes of climate patterns over the land-ocean boundary regions are sensitive to future scenarios of CO2 concentration pathways including extreme cases.

  12. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    SciTech Connect

    Liu, X. H.; Luo, H.; Qu, T. L. Yang, K. Y.; Ding, Z. C.

    2015-10-15

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  13. Electronic Structures and Magnetic Properties of MoS2 Nanostructures: Atomic Defects, Nanoholes, Nanodots and Antidots

    SciTech Connect

    Zhou, Yungang; Yang, Ping; Zu, Haoyue; Gao, Fei; Zu, Xiaotao

    2013-04-24

    MoS2-based nanostructures, including atomic defect, nanohole, nanodot and antidot, are characterized with spin-polarized density functional theory. The S-vacancy defect is more likely to form than the Mo-vacancy defect due to the formation of Mo-Mo metallic bonds. Among different shaped nanoholes and nanodots, triangle ones associated with ferromagnetic characteristic are the most energetically favorable, and exhibit unexpected large spin moment that is scaled linearly with edged length.

  14. Effective Control of the Charge and Magnetic States of Transition-Metal Atoms on Single-Layer Boron Nitride

    SciTech Connect

    Huang, B.; Xiang, H. J.; Yu, J. J.; Wei, S. H.

    2012-05-18

    Developing approaches to effectively control the charge and magnetic states is critical to the use of magnetic nanostructures in quantum information devices but is still challenging. Here we suggest that the magnetic and charge states of transition-metal (TM) doped single-layer boron-nitride (SLBN) systems can be easily controlled by the (internal) defect engineering and (external) electric fields (E{sub ext}). The relative positions and symmetries of the in-gap levels induced by defect engineering and the TM d-orbital energy levels effectively determine the charge states and magnetic properties of the TM/SLBN system. Remarkably, the application of an E{sub ext} can easily control the size of the crystal field splitting of the TM d orbitals and thus, leading to the spin crossover in TM/SLBN, which could be used as E{sub ext}-driven nonvolatile memory devices. Our conclusion obtained from TM/SLBN is valid generally in other TM adsorbed layered semiconductors.

  15. Warm Absorber Diagnostics of AGN Dynamics

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy

    key for validating and testing models. New in this work is treatment of magnetically driven models, self-consistent calculation of the physical properties of the accretion flow and winds and their spectra. This will allow us to test the range of plausible physical origins for warm absorbers.

  16. Closed-form expression for the magnetic shielding constant of the relativistic hydrogenlike atom in an arbitrary discrete energy eigenstate: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function

    NASA Astrophysics Data System (ADS)

    Stefańska, Patrycja

    2016-07-01

    We present analytical derivation of the closed-form expression for the dipole magnetic shielding constant of a Dirac one-electron atom being in an arbitrary discrete energy eigenstate. The external magnetic field, by which the atomic state is perturbed, is assumed to be weak, uniform, and time independent. With respect to the atomic nucleus we assume that it is pointlike, spinless, motionless, and of charge Z e . Calculations are based on the Sturmian expansion of the generalized Dirac-Coulomb Green function [R. Szmytkowski, J. Phys. B 30, 825 (1997), 10.1088/0953-4075/30/4/007; erratum R. Szmytkowski, J. Phys. B 30, 2747(E) (1997), 10.1088/0953-4075/30/11/023], combined with the theory of hypergeometric functions. The final result is of an elementary form and agrees with corresponding formulas obtained earlier by other authors for some particular states of the atom.

  17. Anti-atoms: Gotcha!

    NASA Astrophysics Data System (ADS)

    Surko, Clifford M.

    2011-07-01

    Refined techniques to mix cold antiprotons and positrons in a magnetic bottle show that antihydrogen atoms can be trapped for 15 minutes -- an improvement of four orders of magnitude over previous experiments.

  18. A fast parallel code for calculating energies and oscillator strengths of many-electron atoms at neutron star magnetic field strengths in adiabatic approximation

    NASA Astrophysics Data System (ADS)

    Engel, D.; Klews, M.; Wunner, G.

    2009-02-01

    We have developed a new method for the fast computation of wavelengths and oscillator strengths for medium-Z atoms and ions, up to iron, at neutron star magnetic field strengths. The method is a parallelized Hartree-Fock approach in adiabatic approximation based on finite-element and B-spline techniques. It turns out that typically 15-20 finite elements are sufficient to calculate energies to within a relative accuracy of 10-5 in 4 or 5 iteration steps using B-splines of 6th order, with parallelization speed-ups of 20 on a 26-processor machine. Results have been obtained for the energies of the ground states and excited levels and for the transition strengths of astrophysically relevant atoms and ions in the range Z=2…26 in different ionization stages. Catalogue identifier: AECC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3845 No. of bytes in distributed program, including test data, etc.: 27 989 Distribution format: tar.gz Programming language: MPI/Fortran 95 and Python Computer: Cluster of 1-26 HP Compaq dc5750 Operating system: Fedora 7 Has the code been vectorised or parallelized?: Yes RAM: 1 GByte Classification: 2.1 External routines: MPI/GFortran, LAPACK, PyLab/Matplotlib Nature of problem: Calculations of synthetic spectra [1] of strongly magnetized neutron stars are bedevilled by the lack of data for atoms in intense magnetic fields. While the behaviour of hydrogen and helium has been investigated in detail (see, e.g., [2]), complete and reliable data for heavier elements, in particular iron, are still missing. Since neutron stars are formed by the collapse of the iron cores of massive stars, it may be assumed that their atmospheres contain an iron plasma. Our objective is to fill the gap

  19. Microstructual investigation of mixed rar earth iron boron processed vis melt-spinning and high-pressure gas-atomization for isotrophic bonded permanent magnets

    SciTech Connect

    Buelow, Nicholas Lee

    2005-08-01

    A solid solution of three rare earths (RE) in the RE{sub 2}Fe{sub 14}B structure have been combined to create the novel mixed rare earth iron boron (MRE{sub 2}Fe{sub 14}B) alloy family. MRE{sub 2}Fe{sub 14}B exhibits reduced temperature dependent magnetic properties; remanence and coercivity. The desired form of MRE{sub 2}Fe{sub 14}B is a powder that can be blended with a polymer binder and compression or injection molded to form an isotropic polymer bonded permanent magnet (PBM). Commercially, Nd{sub 2}Fe{sub 14}B is the alloy of choice for PBMs. Powders of Nd{sub 2}Fe{sub 14}B are made via melt-spinning as can be MRE{sub 2}Fe{sub 14}B which allows for direct comparisons. MRE{sub 2}Fe{sub 14}B made using melt-spinning at high wheel speeds is overquenched and must be annealed to an optimal hard magnetic state. Due to the rare earth content in the MRE{sub 2}Fe{sub 14}B powders, they must be protected from the environment in which they operate. This protection is accomplished by using a modified fluidized bed process to grow a protective fluoride coating nominally 15nm thick, to reduce air oxidation. MRE{sub 2}Fe{sub 14}B has demonstrated reduced temperature dependent magnetic properties in ribbon and PBM form. The real challenge has been modifying alloy designs that were successfully melt-spun to be compatible with high-pressure gas-atomization (HPGA). The cooling rates in HPGA are lower than melt-spinning, as the powders are quenched via convective cooling, compared to melt-spinning, which quenches initially by conductive cooling. Early alloy designs, in gas atomized and melt-spun form, did not have similar phase compositions or microstructures. Alloy additions, such as the addition of zirconium as a nucleation catalyst, were successful in creating similar phases and microstructures in the HPGA powders and melt-spun ribbon of the same MRE{sub 2}Fe{sub 14}B composition.

  20. Atomic resolution protein structure determination by three-dimensional transferred echo double resonance solid-state nuclear magnetic resonance spectroscopy

    PubMed Central

    Nieuwkoop, Andrew J.; Wylie, Benjamin J.; Franks, W. Trent; Shah, Gautam J.; Rienstra, Chad M.

    2009-01-01

    We show that quantitative internuclear 15N–13C distances can be obtained in sufficient quantity to determine a complete, high-resolution structure of a moderately sized protein by magic-angle spinning solid-state NMR spectroscopy. The three-dimensional ZF-TEDOR pulse sequence is employed in combination with sparse labeling of 13C sites in the β1 domain of the immunoglobulin binding protein G (GB1), as obtained by bacterial expression with 1,3-13C or 2-13C-glycerol as the 13C source. Quantitative dipolar trajectories are extracted from two-dimensional 15N–13C planes, in which ∼750 cross peaks are resolved. The experimental data are fit to exact theoretical trajectories for spin clusters (consisting of one 13C and several 15N each), yielding quantitative precision as good as 0.1 Å for ∼350 sites, better than 0.3 Å for another 150, and ∼1.0 Å for 150 distances in the range of 5–8 Å. Along with isotropic chemical shift-based (TALOS) dihedral angle restraints, the distance restraints are incorporated into simulated annealing calculations to yield a highly precise structure (backbone RMSD of 0.25±0.09 Å), which also demonstrates excellent agreement with the most closely related crystal structure of GB1 (2QMT, bbRMSD 0.79±0.03 Å). Moreover, side chain heavy atoms are well restrained (0.76±0.06 Å total heavy atom RMSD). These results demonstrate for the first time that quantitative internuclear distances can be measured throughout an entire solid protein to yield an atomic-resolution structure. PMID:19739873

  1. Electronic and magnetic properties of single Fe atoms on a CuN surface: Effects of electron correlations

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Di Marco, I.; Grânäs, O.; Eriksson, O.; Fransson, J.

    2016-04-01

    The electronic structure and magnetic properties of a single Fe adatom on a CuN surface have been studied using density functional theory in the local spin density approximation (LSDA), the LSDA+U approach, and the local density approximation plus dynamical mean-field theory (LDA+DMFT). The impurity problem in LDA+DMFT is solved through exact diagonalization and in the Hubbard-I approximation. The comparison of the one-particle spectral functions obtained from LSDA, LSDA+U, and LDA+DMFT show the importance of dynamical correlations for the electronic structure of this system. Most importantly, we focused on the magnetic anisotropy and found that neither LSDA nor LSDA+U can explain the measured high values of the axial and transverse anisotropy parameters. Instead, the spin excitation energies obtained from our LDA+DMFT approach with exact diagonalization agree significantly better with experimental data. This affirms the importance of treating fluctuating magnetic moments through a realistic many-body treatment when describing this class of nanomagnetic systems. Moreover, it facilitates insight to the role of the hybridization with surrounding orbitals.

  2. Teaching Global Warming

    NASA Astrophysics Data System (ADS)

    Hobson, Art

    2004-05-01

    Every citizen's education should include socially relevant science courses because, as the American Association for the Advancement of Science puts it, "Without a scientifically literate population, the outlook for a better world is not promising." I have developed a conceptual liberal-arts physics course that covers the major principles of classical physics, emphasizes modern/contemporary physics, and includes societal topics such as global warming, ozone depletion, transportation, exponential growth, scientific methodology, risk assessment, nuclear weapons, nuclear power, and the energy future. The societal topics, occupying only about 15% of the class time, appear to be the main cause of the surprising popularity of this course among non-scientists. I will outline some ideas for incorporating global warming into such a course or into any other introductory physics course. For further details, see my textbook Physics: Concepts and Connections (Prentice Hall, 3rd edition 2003).

  3. Analysis of off-axis solenoid fields using the magnetic scalar potential: An application to a Zeeman-slower for cold atoms

    NASA Astrophysics Data System (ADS)

    Muniz, Sérgio R.; Bagnato, Vanderlei S.; Bhattacharya, M.

    2015-06-01

    In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here, we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method does not require integration or knowledge of the current distribution and is presented through practical examples, including a nonuniform finite solenoid used to produce cold atomic beams via laser cooling. These examples allow educators to discuss the nontrivial calculation of fields off-axis using concepts familiar to most students, while offering the opportunity to introduce themes of current modern research.

  4. PERENNIAL WARM-SEASON GRASSES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Warm-season grasses and can be used to augment the forage supply for grazing livestock operations in the northeastern U.S. Much of what is known about warm season grass production and management in the northeastern US was obtained from a soil conservation or wildlife habitat perspective. Warm-seas...

  5. Neutrino-atom collisions

    NASA Astrophysics Data System (ADS)

    Kouzakov, Konstantin A.; Studenikin, Alexander I.

    2016-05-01

    Neutrino-atom scattering provides a sensitive tool for probing nonstandard interactions of massive neutrinos in laboratory measurements. The ionization channel of this collision process plays an important role in experiments searching for neutrino magnetic moments. We discuss some theoretical aspects of atomic ionization by massive neutrinos. We also outline possible manifestations of neutrino electromagnetic properties in coherent elastic neutrino-nucleus scattering.

  6. Spin and orbital magnetic moments and spin anisotropy energies of light rare earth atoms embedded in graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Li, Ya-Jing; Wang, Min; Tang, Meng-yu; Tian, Xing; Gao, Shan; He, Zhen; Li, Ying; Zhou, Tie-Ge

    2016-01-01

    The geometries, electronic structures, spin magnetic moments (SMMs), orbital magnetic moments (OMMs) and spin anisotropy energies (SAEs) of light rare earth atoms (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd) embedded in graphene were studied by using first-principles calculations based on Density Functional Theory (DFT). The spin-orbital coupling effect was taken into account and GGA+U method was adopted to describe the strongly localized and correlated 4f electrons. There is a significant deformation of the graphene plane after doping and optimization. The deformation of Gd doped graphene is the largest, while Eu the smallest. The results show that the valence is +3 for La, Ce, Pr, Nd, Pm, Sm and Gd, and +2 for Eu. Except Eu and Gd, there are obvious OMMs. When the spin is in the Z direction, the OMMs are -0.941 μB, -1.663 μB, -3.239 μB, -3.276 μB and -3.337 μB for Ce, Pr, Nd, Pm and Sm, respectively, and point the opposite direction of SMMs. All the doped systems except Gd show considerable SAEs. For Ce, Pr, Nd, Pm, Sm, and Eu, the SAEs are -0.928 meV, 20.941 meV, -8.848 meV, 7.855 meV, 75.070 meV and 0.810 meV, respectively. When the spin orientation is different, different orbital angular moments lead to apparent charge density difference of the 4f atoms, which can also explain the origin of SAEs.

  7. Global Warming And Meltwater

    NASA Astrophysics Data System (ADS)

    Bratu, S.

    2012-04-01

    In order to find new approaches and new ideas for my students to appreciate the importance of science in their daily life, I proposed a theme for them to debate. They had to search for global warming information and illustrations in the media, and discuss the articles they found in the classroom. This task inspired them to search for new information about this important and timely theme in science. I informed my students that all the best information about global warming and meltwater they found would be used in a poster that would help us to update the knowledge base of the Physics laboratory. I guided them to choose the most eloquent images and significant information. Searching and working to create this poster, the students arrived to better appreciate the importance of science in their daily life and to critically evaluate scientific information transmitted via the media. In the poster we created, one can find images, photos and diagrams and some interesting information: Global warming refers to the rising average temperature of the Earth's atmosphere and oceans and its projected evolution. In the last 100 years, the Earth's average surface temperature increased by about 0.8 °C with about two thirds of the increase occurring over just the last three decades. Warming of the climate system is unequivocal, and scientists are more than 90% certain most of it is caused by increasing concentrations of greenhouse gases produced by human activities such as deforestation and burning fossil fuel. They indicate that during the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C for the lowest emissions scenario and 2.4 to 6.4 °C for the highest predictions. An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, and potentially result in expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing decrease of

  8. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3.

    PubMed

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J L; Zhong, Ruidan; Schneeloch, John A; Liu, Tiansheng; Valla, Tonica; Tranquada, John M; Gu, Genda; Davis, J C Séamus

    2015-02-01

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a "Dirac-mass gap" in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in the ferromagnetic TI Cr0.08(Bi0.1Sb0.9)1.92Te3. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship [Formula: see text] is confirmed throughout and exhibits an electron-dopant interaction energy J* = 145 meV·nm(2). These observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential. PMID:25605947

  9. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3

    DOE PAGESBeta

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J. L.; Zhong, Ruidan D.; Schneeloch, John A.; Liu, Tiansheng S.; Valla, Tonica; Tranquada, John M.; Gu, Genda D.; et al

    2015-01-20

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a “Dirac-mass gap” in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in themore » ferromagnetic TI Cr₀.₀₈(Bi₀.₁Sb₀.₉)₁.₉₂Te₃. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship Δ(r)∝n(r) is confirmed throughout and exhibits an electron–dopant interaction energy J* = 145 meV·nm². In addition, these observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.« less

  10. A highly optimized code for calculating atomic data at neutron star magnetic field strengths using a doubly self-consistent Hartree-Fock-Roothaan method

    NASA Astrophysics Data System (ADS)

    Schimeczek, C.; Engel, D.; Wunner, G.

    2012-07-01

    account the shielding of the core potential for outer electrons by inner electrons, and an optimal finite-element decomposition of each individual longitudinal wave function. These measures largely enhance the convergence properties compared to the previous code, and lead to speed-ups by factors up to two orders of magnitude compared with the implementation of the Hartree-Fock-Roothaan method used by Engel and Wunner in [D. Engel, G. Wunner, Phys. Rev. A 78 (2008) 032515]. New version program summaryProgram title: HFFER II Catalogue identifier: AECC_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: v 55 130 No. of bytes in distributed program, including test data, etc.: 293 700 Distribution format: tar.gz Programming language: Fortran 95 Computer: Cluster of 1-13 HP Compaq dc5750 Operating system: Linux Has the code been vectorized or parallelized?: Yes, parallelized using MPI directives. RAM: 1 GByte per node Classification: 2.1 External routines: MPI/GFortran, LAPACK, BLAS, FMlib (included in the package) Catalogue identifier of previous version: AECC_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 302 Does the new version supersede the previous version?: Yes Nature of problem: Quantitative modellings of features observed in the X-ray spectra of isolated magnetic neutron stars are hampered by the lack of sufficiently large and accurate databases for atoms and ions up to the last fusion product, iron, at strong magnetic field strengths. Our code is intended to provide a powerful tool for calculating energies and oscillator strengths of medium-Z atoms and ions at neutron star magnetic field strengths with sufficient accuracy in a routine way to create such databases. Solution method: The

  11. Experimental investigation of inhomogeneities, nanoscopic phase separation, and magnetism in arc melted Fe-Cu metals with equal atomic ratio of the constituents

    NASA Astrophysics Data System (ADS)

    Hassnain Jaffari, G.; Aftab, M.; Anjum, D. H.; Cha, Dongkyu; Poirier, Gerald; Ismat Shah, S.

    2015-12-01

    Composition gradient and phase separation at the nanoscale have been investigated for arc-melted and solidified with equiatomic Fe-Cu. Diffraction studies revealed that Fe and Cu exhibited phase separation with no trace of any mixing. Microscopy studies revealed that immiscible Fe-Cu form dense bulk nanocomposite. The spatial distribution of Fe and Cu showed existence of two distinct regions, i.e., Fe-rich and Cu-rich regions. Fe-rich regions have Cu precipitates of various sizes and different shapes, with Fe forming meshes or channels greater than 100 nm in size. On the other hand, the matrix of Cu-rich regions formed strips with fine strands of nanosized Fe. Macromagnetic response of the system showed ferromagnetic behavior with a magnetic moment being equal to about 2.13 μB/ Fe atom and a bulk like negligible value of coercivity over the temperature range of 5-300 K. Anisotropy constant has been calculated from various laws of approach to saturation, and its value is extracted to be equal to 1350 J/m3. Inhomogeneous strain within the Cu and Fe crystallites has been calculated for the (unannealed) sample solidified after arc-melting. Annealed sample also exhibited local inhomogeneity with removal of inhomogeneous strain and no appreciable change in magnetic character. However, for the annealed sample phase separated Fe exhibited homogenous strain.

  12. Preparation of modified magnetic nanoparticles as a sorbent for the preconcentration and determination of cadmium ions in food and environmental water samples prior to flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mirabi, Ali; Dalirandeh, Zeinab; Rad, Ali Shokuhi

    2015-05-01

    A new method has been developed for the separation/preconcentration of trace level cadmium ions using diphenyl carbazone/sodium dodecyl sulfate immobilized on magnetic nanoparticle Fe3O4 as a new sorbent SPE and their determination by flame atomic absorption spectrometry (FAAS). Synthesized nanoparticle was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Various influencing parameters on the separation and preconcentration of trace level cadmium ions such as, pH value, amount of nanoparticles, amount of diphenyl carbazone, condition of eluting solution, the effects of matrix ions were examined. The cadmium ions can be eluted from the modified magnetic nanoparticle using 1 mol L-1 HCl as a desorption reagent. The detection limit of this method for cadmium was 3.71 ng ml-1 and the R.S.D. was 0.503% (n=6). The advantages of this new method include rapidity, easy preparation of sorbents and a high concentration factor. The proposed method has been applied to the determination of Cd ions at trace levels in real samples such as, green tea, rice, tobacco, carrot, lettuce, ginseng, spice, tap water, river water, sea water with satisfactory results.

  13. MAGNETS

    DOEpatents

    Hofacker, H.B.

    1958-09-23

    This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

  14. Global warming - A reduced threat

    SciTech Connect

    Michaels, P.J.; Stooksbury, D.E. )

    1992-10-01

    Issues associated with global warming are analyzed focusing on global and hemispheric temperature histories and trace gas concentrations; artificial warming from urban heat islands; high-latitude and diurnal temperatures; recent climate models; direct effects on vegetation of an increase in carbon dioxide; and compensatory cooling from other industrial products. Data obtained indicate that anthropogenerated sulfate emissions are mitigating some of the warming, and that increased cloudiness as a result of these emissions will further enhance night, rather than day, warming. It is noted that the sulfate emissions are not sufficient to explain all of the night warming. The sensitivity of climate to anthropogenerated aerosols, and the general lack of previously predicted warming, could drastically alter the debate on global warming in favor of less expensive policies. 61 refs.

  15. Trapping deuterium atoms

    SciTech Connect

    Wiederkehr, A. W.; Hogan, S. D.; Lambillotte, B.; Andrist, M.; Schmutz, H.; Agner, J.; Salathe, Y.; Merkt, F.

    2010-02-15

    Cold deuterium atoms in a supersonic beam have been decelerated from an initial velocity of 475 m/s to zero velocity in the laboratory frame using a 24-stage Zeeman decelerator. The atoms have been loaded in a magnetic quadrupole trap at a temperature of {approx}100 mK and an initial density of {approx}10{sup 6} cm{sup -3}. Efficient deceleration was achieved by pulsing the magnetic fields in the decelerator solenoids using irregular sequences of phase angles. Trap loading was optimized by monitoring and suppressing the observed reflection of the atoms by the field gradient of the back solenoid of the trap.

  16. Sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection

    PubMed Central

    Liang, Pei; Kang, Caiyan; Yang, Enjian; Ge, Xiaoxiao; Du, Dan; Lin, Yuehe

    2016-01-01

    We developed a new magnetic nanoparticles sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for quantification of organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form TiO2-MNPs/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma. PMID:26953358

  17. In situ emulsification microextraction using a dicationic ionic liquid followed by magnetic assisted physisorption for determination of lead prior to micro-sampling flame atomic absorption spectrometry.

    PubMed

    Shokri, Masood; Beiraghi, Asadollah; Seidi, Shahram

    2015-08-19

    For the first time, a simple and efficient in situ emulsification microextraction method using a dicationic ionic liquid followed by magnetic assisted physisorption was presented to determine trace amounts of lead. In this method, 400 μL of 1.0 mol L(-1) lithium bis (trifluoromethylsulfonyl) imide aqueous solution, Li[NTf2], was added into the sample solution containing 100 μL of 1.0 mol L(-1) 1,3-(propyl-1,3-diyl) bis (3-methylimidazolium) chloride, [pbmim]Cl2, to form a water immiscible ionic liquid, [pbmim][NTf2]2. This new in situ formed dicationic ionic liquid was applied as the acceptor phase to extract the lead-ammonium pyrrolidinedithiocarbamate (Pb-APDC) complexes from the sample solution. Subsequently, 30 mg of Fe3O4 magnetic nanoparticles (MNPs) were added into the sample solution to collect the fine droplets of [pbmim][NTf2]2, physisorptively. Finally, MNPs were eluted by acetonitrile, separated by an external magnetic field and the obtained eluent was subjected to micro-sampling flame atomic absorption spectrometry (FAAS) for further analysis. Comparing with other microextraction methods, no special devices and centrifugation step are required. Parameters influencing the extraction efficiency such as extraction time, pH, concentration of chelating agent, amount of MNPs and coexisting interferences were studied. Under the optimized conditions, this method showed high extraction recovery of 93% with low LOD of 0.7 μg L(-1). Good linearity was obtained in the range of 2.5-150 μg L(-1) with determination coefficient (r(2)) of 0.9921. Relative standard deviation (RSD%) for seven repeated measurements at the concentration of 10 μg L(-1) was 4.1%. Finally, this method was successfully applied for determination of lead in some water and plant samples. PMID:26343434

  18. A sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection.

    PubMed

    Liang, Pei; Kang, Caiyan; Yang, Enjian; Ge, Xiaoxiao; Du, Dan; Lin, Yuehe

    2016-04-01

    We developed a new magnetic nanoparticle sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for the quantification of an organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form a TiO2-MNP/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad range of OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma. PMID:26953358

  19. Microwave electric field sensing with Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Stack, Daniel T.; Kunz, Paul D.; Meyer, David H.; Solmeyer, Neal

    2016-05-01

    Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.

  20. Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution

    SciTech Connect

    Karcı, Özgür; Dede, Münir

    2014-10-01

    We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ~12 fm/√Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system.

  1. Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution.

    PubMed

    Karcı, Özgür; Dede, Münir; Oral, Ahmet

    2014-10-01

    We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ∼12 fm/√Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system. PMID:25362401

  2. FLATs: Warming Up

    NASA Astrophysics Data System (ADS)

    Calzetti, Daniela

    1997-07-01

    The purpose of this proposal is to monitor the flat fields during the interval between the end of science observations and the exhaustion of cryogen and subsequent warming of the dewar to > 100K. These flats will provide a monitor for particulate comtamination {GROT} and detector lateral position {from the coronagraphic spot and FDA vignetting}. They will provide some measure of relative {flat field} and absolute QE variation as a function of temperature. When stars are visible they might provide a limited degree of focus determination.

  3. FLATs: Warming Up - continuation

    NASA Astrophysics Data System (ADS)

    Calzetti, Daniela

    1997-07-01

    The purpose of this proposal is to monitor the flat fields during the interval between the end of science observations and the exhaustion of cryogen and subsequent warming of the dewar to > 100K. These flats will provide a monitor for particulate comtamination {GROT} and detector lateral position {from the coronagraphic spot and FDA vignetting}. They will provide some measure of relative {flat field} and absolute QE variation as a function of temperature. When stars are visible they might provide a limited degree of focus determination.

  4. Rapid prototyping of versatile atom chips for atom interferometry applications.

    NASA Astrophysics Data System (ADS)

    Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

    2016-05-01

    We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

  5. Quantum electrodynamics effects on NMR magnetic shielding constants of He-like and Be-like atomic systems

    NASA Astrophysics Data System (ADS)

    Gimenez, Carlos A.; Kozioł, Karol; Aucar, Gustavo A.

    2016-03-01

    NMR shielding constants for He- and Be-like atomic systems of Ne, Ar, Kr, Xe, and Rn have been calculated at the random-phase-approximation level of approach, including an estimation of QED corrections within the polarization propagator formalism. We show that QED effects enhance electron correlation when Z becomes heavier, which happens with relativistic effects, and also that QED effects become smaller when going from more to less ionized systems. We studied two- and four-electron systems. Then such studies could easily be generalized to other many-electron systems. Results of calculations with our relatively simple model, which includes QED and electron correlation effects on the same theoretical grounds, have a summarized error in the range from 10% (for Ne) up to 24% (for Rn), so that our accuracy is a little lower than for calculations on H-like systems. Our findings should stimulate the development and/or the application of more rigorous formalisms to get more accurate QED corrections to response properties in many-electron systems.

  6. Is Global Warming Accelerating?

    NASA Astrophysics Data System (ADS)

    Shukla, J.; Delsole, T. M.; Tippett, M. K.

    2009-12-01

    A global pattern that fluctuates naturally on decadal time scales is identified in climate simulations and observations. This newly discovered component, called the Global Multidecadal Oscillation (GMO), is related to the Atlantic Meridional Oscillation and shown to account for a substantial fraction of decadal fluctuations in the observed global average sea surface temperature. IPCC-class climate models generally underestimate the variance of the GMO, and hence underestimate the decadal fluctuations due to this component of natural variability. Decomposing observed sea surface temperature into a component due to anthropogenic and natural radiative forcing plus the GMO, reveals that most multidecadal fluctuations in the observed global average sea surface temperature can be accounted for by these two components alone. The fact that the GMO varies naturally on multidecadal time scales implies that it can be predicted with some skill on decadal time scales, which provides a scientific rationale for decadal predictions. Furthermore, the GMO is shown to account for about half of the warming in the last 25 years and hence a substantial fraction of the recent acceleration in the rate of increase in global average sea surface temperature. Nevertheless, in terms of the global average “well-observed” sea surface temperature, the GMO can account for only about 0.1° C in transient, decadal-scale fluctuations, not the century-long 1° C warming that has been observed during the twentieth century.

  7. Warm Inflation Model Building

    NASA Astrophysics Data System (ADS)

    Bastero-Gil, Mar; Berera, Arjun

    We review the main aspects of the warm inflation scenario, focusing on the inflationary dynamics and the predictions related to the primordial spectrum of perturbations, to be compared with the recent cosmological observations. We study in detail three different classes of inflationary models, chaotic, hybrid models and hilltop models, and discuss their embedding into supersymmetric models and the consequences for model building of the warm inflationary dynamics based on first principles calculations. Due to the extra friction term introduced in the inflaton background evolution generated by the dissipative dynamics, inflation can take place generically for smaller values of the field, and larger values of couplings and masses. When the dissipative dynamics dominates over the expansion, in the so-called strong dissipative regime, inflation proceeds with sub-Planckian inflaton values. Models can be naturally embedded into a supergravity framework, with SUGRA corrections suppressed by the Planck mass now under control, for a larger class of Kähler potentials. In particular, this provides a simpler solution to the "eta" problem in supersymmetric hybrid inflation, without restricting the Kähler potentials compatible with inflation. For chaotic models dissipation leads to a smaller prediction for the tensor-to-scalar ratio and a less tilted spectrum when compared to the cold inflation scenario. We find in particular that a small component of dissipation renders the quartic model now consistent with the current CMB data.

  8. Optical magnetic resonances induced by the interference of reactive components in the near radiation-field zone of atoms in a glow discharge of a mixture of even neon isotopes

    NASA Astrophysics Data System (ADS)

    Saprykin, E. G.

    2016-02-01

    Four types of anomalous optical magnetic resonances shifted with respect to the zero magnetic field and with different shapes are found in radiation of a glow discharge in a mixture of even neon isotopes placed in a swept longitudinal magnetic field. This testifies to the manifestation of collective processes of synchronous light emission by oscillators belonging to isotopically different spatially separated atoms in discharge plasma. The origin of resonances is associated with nonstationary interference of reactive fields in the near radiation-field zones of emission of atoms, averaged over the lifetime of the fields (interference), while different types of resonances are associated with different methods of synchronization of the phases of the fields.

  9. Magnetic dipolar and quadrupolar transitions in two-electron atoms under exponential-cosine-screened Coulomb potential

    SciTech Connect

    Modesto-Costa, Lucas; Canuto, Sylvio; Mukherjee, Prasanta K.

    2015-03-15

    A detailed investigation of the magnetic dipolar and quadrupolar excitation energies and transition probabilities of helium isoelectronic He, Be{sup 2+}, C{sup 4+}, and O{sup 6+} have been performed under exponential cosine screened Coulomb potential generated in a plasma environment. The low-lying excited states 1s{sup 2}:{sup 1}S{sup e} → 1sns:{sup 3}S{sup e}{sub 0}, and 1snp:{sup 3}P{sup o}{sub 2} (n = 2, 3, 4, and 5) are considered. The variational time-dependent coupled Hartree-Fock scheme has been used. The effect of the confinement produced by the potential on the structural properties is investigated for increasing coupling strength of the plasma. It is noted that there is a gradual destabilization of the energy of the system with the reduction of the ionization potential and the number of excited states. The effect of the screening enhancement on the excitation energies and transition probabilities has also been investigated and the results compared with those available for the free systems and under the simple screened Coulomb potential.

  10. Microfabricated Spin Polarized Atomic Magnetometers

    NASA Astrophysics Data System (ADS)

    Jimenez Martinez, Ricardo

    Spin polarized atomic magnetometers involve the preparation of atomic spins and their detection for monitoring magnetic fields. Due to the fact that magnetic fields are ubiquitous in our world, spin polarized atomic magnetometers are used in a wide range of applications from the detection of magnetic fields generated by the human heart and brain to the detection of nuclear magnetic resonance. In this thesis we developed microfabricated spin polarized atomic magnetometers. These sensors are based on optical pumping and spin-exchange collisions between alkali atoms and noble gases contained in microfabricated millimeter-scale vapor cells. In the first part of the thesis, we improved different features of current microfabricated optical magnetometers. Specifically, we improved the bandwidth of these devices, without degrading their magnetic field sensitivity, by broadening their magnetic resonance through spin-exchange collisions between alkali atoms. We also implemented all-optical excitation techniques to avoid problems, such as the magnetic perturbation of the environment, induced by the radio-frequency fields used in some of these sensors. In the second part of the thesis we demonstrated a microfluidic chip for the optical production and detection of hyperpolarized Xe gas through spin-exchange collisions with optically pumped Rb atoms. These devices are critical for the widespread use of spin polarized atomic magnetometers in applications requiring simple, compact, low-cost, and portable instrumentation.

  11. Magnetic solid-phase extraction combined with graphite furnace atomic absorption spectrometry for speciation of Cr(III) and Cr(VI) in environmental waters.

    PubMed

    Jiang, Hong-mei; Yang, Ting; Wang, Yan-hong; Lian, Hong-zhen; Hu, Xin

    2013-11-15

    A new approach of magnetic solid phase extraction (MSPE) coupled with graphite furnace atomic absorption spectrometry (GFAAS) has been developed for the speciation of Cr(III) and Cr(VI) using zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles (Zincon-Si-MNPs) as the MSPE absorbent. Cr(III) was quantitatively reserved on the absorbent at pH 9.1 while total Cr was reserved at pH 6.5. The absorbed Cr species were eluted by using 2 mol/L HCl and detected by GFAAS. The concentration of Cr(VI) could be calculated by subtracting Cr(III) from total Cr. All the parameters affecting the separation and extraction efficiency of Cr species such as pH, extraction time, concentration and volume of eluent, sample volume and influence of co-existing ions were systematically examined and the optimized conditions were established accordingly. The detection limit (LOD) of the method was 0.016 and 0.011 ng mL(-1) for Cr(III) and Cr(VI), respectively, with the enrichment factor of 100 and 150. The precisions of this method (Relative standard deviation, RSD, n=7) for Cr(III) and Cr(VI) at 0.1 ng mL(-1) were 6.0% and 6.2%, respectively. In order to validate the proposed method, a certified reference material of environmental water was analyzed, and the result of Cr speciation was in good agreement with the certified value. This MSPE-GFAAS method has been successfully applied for the speciation of Cr(III) and Cr(VI) in lake and tap waters with the recoveries of 88-109% for the spiked samples. Moreover, the MSPE separation mechanism of Cr(III) and Cr(VI) based on their adsorption-desorption on Zincon-Si-MNPs has been explained through various spectroscopic characterization. PMID:24148416

  12. Global Warming on Triton

    NASA Technical Reports Server (NTRS)

    Elliot, J. L.; Hammel, H. B.; Wasserman, L. H.; Franz, O. G.; McDonald, S. W.; Person, M. J.; Olkin, C. B.; Dunham, E. J.; Spencer, J. R.; Stansberry, J. A.; Buie, M. W.; Pasachoff, J. M.; Babcock, B. A.; McConnochie, T. H.

    1998-01-01

    Triton, Neptune's largest moon, has been predicted to undergo significant seasonal changes that would reveal themselves as changes in its mean frost temperature. But whether this temperature should at the present time be increasing, decreasing or constant depends on a number of parameters (such as the thermal properties of the surface, and frost migration patterns) that are unknown. Here we report observations of a recent stellar occultation by Triton which, when combined with earlier results, show that Triton has undergone a period of global warming since 1989. Our most conservative estimates of the rate of temperature and surface-pressure increase during this period imply that the atmosphere is doubling in bulk every 10 years, significantly faster than predicted by any published frost model for Triton. Our result suggests that permanent polar caps on Triton play a c dominant role in regulating seasonal atmospheric changes. Similar processes should also be active on Pluto.

  13. Global warming challenge

    SciTech Connect

    Hengeveld, H. )

    1994-11-01

    Global warming will necessitate significant adjustments in Canadian society and its economy. In 1979, the Canadian federal government created its Canadian Climate Program (CCP) in collaboration with other agencies, institutions, and individuals. It sought to coordinate national efforts to understand global and regional climate, and to promote better use of the emerging knowledge. Much of the CCP-coordinated research into sources and sinks of greenhouse gases interfaces with other national and international programs. Other researchers have become involved in the Northern Wetlands Study, a cooperative United States-Canada initiative to understand the role of huge northern bogs and muskegs in the carbon cycle. Because of the need to understand how the whole, linked climate system works, climate modeling emerged as a key focus of current research. 35 refs., 4 figs.

  14. Warm waters, bleached corals

    SciTech Connect

    Roberts, L.

    1990-10-12

    Two researchers, Tom Goreau of the Discovery Laboratory in Jamaica and Raymond Hayes of Howard University, claim that they have evidence that nearly clinches the temperature connection to the bleached corals in the Caribbean and that the coral bleaching is an indication of Greenhouse warming. The incidents of scattered bleaching of corals, which have been reported for decades, are increasing in both intensity and frequency. The researchers based their theory on increased temperature of the seas measured by satellites. However, some other scientists feel that the satellites measure the temperature of only the top few millimeters of the water and that since corals lie on reefs perhaps 60 to 100 feet below the ocean surface, the elevated temperatures are not significant.

  15. Method of performing MRI with an atomic magnetometer

    SciTech Connect

    Savukov, Igor Mykhaylovich; Matlashov, Andrei Nikolaevich; Espy, Michelle A; Volegov, Petr Lvovich; Kraus, Jr., Robert Henry; Zotev, Vadim Sergeyevich

    2013-08-27

    A method and apparatus are provided for performing an in-situ magnetic resonance imaging of an object. The method includes the steps of providing an atomic magnetometer, coupling a magnetic field generated by magnetically resonating samples of the object through a flux transformer to the atomic magnetometer and measuring a magnetic resonance of the atomic magnetometer.

  16. Method of performing MRI with an atomic magnetometer

    DOEpatents

    Savukov, Igor Mykhaylovich; Matlashov, Andrei Nikolaevich; Espy, Michelle A.; Volegov, Petr Lvovich; Kraus, Jr., Robert Henry; Zotev, Vadim Sergeyevich

    2012-11-06

    A method and apparatus are provided for performing an in-situ magnetic resonance imaging of an object. The method includes the steps of providing an atomic magnetometer, coupling a magnetic field generated by magnetically resonating samples of the object through a flux transformer to the atomic magnetometer and measuring a magnetic resonance of the atomic magnetometer.

  17. Interacting warm dark matter

    SciTech Connect

    Cruz, Norman; Palma, Guillermo; Zambrano, David; Avelino, Arturo E-mail: guillermo.palma@usach.cl E-mail: avelino@fisica.ugto.mx

    2013-05-01

    We explore a cosmological model composed by a dark matter fluid interacting with a dark energy fluid. The interaction term has the non-linear λρ{sub m}{sup α}ρ{sub e}{sup β} form, where ρ{sub m} and ρ{sub e} are the energy densities of the dark matter and dark energy, respectively. The parameters α and β are in principle not constrained to take any particular values, and were estimated from observations. We perform an analytical study of the evolution equations, finding the fixed points and their stability properties in order to characterize suitable physical regions in the phase space of the dark matter and dark energy densities. The constants (λ,α,β) as well as w{sub m} and w{sub e} of the EoS of dark matter and dark energy respectively, were estimated using the cosmological observations of the type Ia supernovae and the Hubble expansion rate H(z) data sets. We find that the best estimated values for the free parameters of the model correspond to a warm dark matter interacting with a phantom dark energy component, with a well goodness-of-fit to data. However, using the Bayesian Information Criterion (BIC) we find that this model is overcame by a warm dark matter – phantom dark energy model without interaction, as well as by the ΛCDM model. We find also a large dispersion on the best estimated values of the (λ,α,β) parameters, so even if we are not able to set strong constraints on their values, given the goodness-of-fit to data of the model, we find that a large variety of theirs values are well compatible with the observational data used.

  18. A Warm Magnetoactive Plasma in a Large Volume of Space

    NASA Technical Reports Server (NTRS)

    Heiles, C.

    1984-01-01

    A diffuse ionized warm gas fills a large volume of space in the general direction of Radio Loop II. There are three types of observational evidence: Faraday rotation measures (RM's) of extragalactic sources; emission measures (EM's) derived from the H alpha emission line in the diffuse interstellar medium; and magnetic field strengths in HI clouds derived from Zeeman splitting observations.

  19. Policy implications of greenhouse warming

    NASA Astrophysics Data System (ADS)

    Coppock, Rob

    1992-03-01

    A study panel of the National Academy of Sciences, National Academy of Engineering, and Institute of Medicine recently issued the report Policy Implications of Greenhouse Warming. That report examined relevant scientific knowldeg and evidence about the potential of greenhouse warming, and assayed actions that could slow the onset of warming (mitigation policies) or help human and natural systems of plants and animals adapt to climatic changes (adaptation policies). The panel found that, even given the considerable uncertainties knowledge of the relevant phenomena, greenhouse warming poses a threat sufficient to merit prompt action. People in this country could probably adapt to the changes likely to accompany greenhouse warming. The costs, however, could be substantial. Investment in mitigation acts as insurance protection against the great uncertainties and the possibility of dramatic surprises. The panel found mitigation options that could reduce U.S. emissions by an estimated 10 to 40 percent at modest cost.

  20. A RELATION BETWEEN THE WARM NEUTRAL AND IONIZED MEDIA OBSERVED IN THE CANADIAN GALACTIC PLANE SURVEY

    SciTech Connect

    Foster, T.; Kothes, R.; Brown, J. C.

    2013-08-10

    We report on a comparison between 21 cm rotation measure (RM) and the optically thin atomic hydrogen column density (N{sub H{sub I}}({tau} {yields} 0)) measured toward unresolved extragalactic sources in the Galactic plane of the northern sky. H I column densities integrated to the Galactic edge are measured immediately surrounding each of nearly 2000 sources in 1 arcmin 21 cm line data, and are compared to RMs observed from polarized emission of each source. RM data are binned in column density bins 4 Multiplication-Sign 10{sup 20} cm{sup -2} wide, and one observes a strong relationship between the number of hydrogen atoms in a 1 cm{sup 2} column through the plane and the mean RM along the same line of sight and path length. The relationship is linear over one order of magnitude (from 0.8 to 14 Multiplication-Sign 10{sup 21} atoms cm{sup -2}) of column densities, with a constant RM/N{sub H{sub I}}{approx} -23.2 {+-} 2.3 rad m{sup -2}/10{sup 21} atoms cm{sup -2}, and a positive RM of 45.0 {+-} 13.8 rad m{sup -2} in the presence of no atomic hydrogen. This slope is used to calculate a mean volume-averaged magnetic field in the second quadrant of (B{sub Parallel-To }) {approx}1.0 {+-} 0.1 {mu}G directed away from the Sun, assuming an ionization fraction of 8% (consistent with the warm-neutral medium; WNM). The remarkable consistency between this field and (B) = 1.2 {mu}G found with the same RM sources and a Galactic model of dispersion measures (DMs) suggests that electrons in the partially ionized WNM are mainly responsible for pulsar DMs, and thus the partially ionized WNM is the dominant form of the magneto-ionic interstellar medium.