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Full-Text Articles in Physics

Temporal Characterization Of A Self-Modulated Laser Wakefield, S.P. Le Blanc, M.C. Downer, R. Wagner, Shouyuan Chen, Anatoly Maksimchuk, G. Mourou, Donald P. Umstadter Dec 1996

Temporal Characterization Of A Self-Modulated Laser Wakefield, S.P. Le Blanc, M.C. Downer, R. Wagner, Shouyuan Chen, Anatoly Maksimchuk, G. Mourou, Donald P. Umstadter

Donald Umstadter Publications

The temporal envelope of plasma density oscillations in the wake of an intense (l∼4×1018 W/cm2, λ = 1 μm) laser pulse (400 fs) is measured using forward Thomson scattering from a copropagating, frequency-doubled probe pulse. The wakefield oscillations in a fully ionized helium plasma (ne = 3×1019 cm-3) are observed to reach maximum amplitude ( δne/ne∼0.1) 300 fs after the pump pulse. The wakefield growth ( 3.5 ps-1) and decay ( 1.9 ps-1) rates are consistent with the forward Raman scattering instability and Landau damping, respectively.


Strain-Induced Distortion Of The Bulk Bands Of Gadolinium, Carlo Waldfried, D.N. Mcilroy, C.W. Hutchings, Peter A. Dowben Dec 1996

Strain-Induced Distortion Of The Bulk Bands Of Gadolinium, Carlo Waldfried, D.N. Mcilroy, C.W. Hutchings, Peter A. Dowben

Peter Dowben Publications

Thin films of gadolinium, approximately 8 ML thick, have been grown on the corrugated (112) surface of molybdenum and the electronic structure has been investigated with angle-resolved photoelectron spectroscopy. The unfavorable lattice match between the ‘‘steplike’’ Mo(112) substrate and the preferred hexagonally ordered Gd film results in an incommensurate Gd structure that appears to be ordered, but strained along the direction of the corrugations. The hexagonal Gd lattice is expanded by more than 20% along the ‘‘step’’ lines of the substrate, as determined from the reduced Brillouin-zone size along the ΓΣM high-symmetry line and low-energy electron diffraction. The induced ...


Comparison Of The Temperature-Dependent Electronic Structure Of The Perovskites La0.65Ca0.35Mno3 (A=Ca, Ba), D.N. Mcilroy, C. Waldfried, Jiandi Zhang, Jaewu Choi, F. Foong, Sy_Hwang Liou, Peter A. Dowben Dec 1996

Comparison Of The Temperature-Dependent Electronic Structure Of The Perovskites La0.65Ca0.35Mno3 (A=Ca, Ba), D.N. Mcilroy, C. Waldfried, Jiandi Zhang, Jaewu Choi, F. Foong, Sy_Hwang Liou, Peter A. Dowben

Peter Dowben Publications

The electronic band structure and the local screening effects of the transition-metal perovskites La0.65A0.35MnO3 (A=Ba and Ca ) have been examined across the coupled magnetic-metallic phase transition using the techniques of angle-resolved photoemission, resonance photoemission, and inverse photoemission. Temperature-dependent band shifts of the eg and t2g bands of La0.65Ca0.35MnO3 have been observed. These changes in the observed electronic structure correlate with the phase transition, and are in qualitatively agreement with the predicted behavior associated with double exchange coupled with a dynamic Jahn-Teller distortion. Similar ...


Neutron Scattering Study Of Transverse Magnetism, Christian Binek, T. Kato, Wolfgang Kleemann, O. Petracic, D. Bertrand, F. Bourdarot, P. Burlet, H. Aruga Katori, K. Katsumata, K. Prokes, S. Welzel Dec 1996

Neutron Scattering Study Of Transverse Magnetism, Christian Binek, T. Kato, Wolfgang Kleemann, O. Petracic, D. Bertrand, F. Bourdarot, P. Burlet, H. Aruga Katori, K. Katsumata, K. Prokes, S. Welzel

Christian Binek Publications

In order to clarify the nature of the additional phase transition at H1 (T) < Hc (T) of the layered antiferromagnetic (AF) insulator FeBr2 as found by Aruga Katori et al. (1996) we measured the intensity of different Bragg-peaks in different scattering geometries. Transverse AF ordering is observed in both AF phases, AFI and AFII. Its order parameter exhibits a peak at T1 = T (H1) in temperature scans and does not vanish in zero field. Possible origins of the step-like increase of the transverse ferromagnetic ordering induced by a weak in-plane field component when entering AFI ...


An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver Dec 1996

An Inline Optical Electron Polarimeter, K. W. Trantham, Timothy J. Gay, R. J. Vandiver

Timothy J. Gay Publications

The design and operation of a simple inline optical electron polarimeter is presented. It is based on exchange excitation of ground state neon atoms. The electron polarization is determined from the degree of circular polarization of the subsequent 2p53p 3D3→2p53s 3P2 (6402 Å) fluorescence. This device can characterize both longitudinally and transversely polarized electron beams in a nondestructive fashion, and is inexpensive and easily constructed.


The Behlen Observatory Variable Star Survey, Iv, Edward G. Schmidt, Anil Seth Dec 1996

The Behlen Observatory Variable Star Survey, Iv, Edward G. Schmidt, Anil Seth

Edward Schmidt Publications

Finding charts, accurate coordinates, and light curves are presented for 106 variable stars including 6 which are newly discovered. Parameters descriptive of the light curves are tabulated including periods for 16 stars which lacked them. The periods from the General Catalog of Variable Stars for ten stars were found to be seriously in error. The classification of the stars is discussed. Revisions or refinements of the classifications from the General Catalogue of Variable Stars are suggested for 20 stars and classifications are given for 7 which were previously unclassified. 15%-23% of the Bailey type ab RR Lyrae stars show ...


Stars Classified As Constant In The General Catalogue Of Variable Stars, Ii, Edward G. Schmidt Dec 1996

Stars Classified As Constant In The General Catalogue Of Variable Stars, Ii, Edward G. Schmidt

Edward Schmidt Publications

Photometric observations have been made of 36 stars classified as CST or CST: in the General Catalogue of Variable Stars. Six of these stars are found to vary and three others were deemed possible variables. Of the certain variables, two (MR Her and TY Sge) are red pulsators, one (V1585 Cyg) is a rapid irregular variable, one is apparently a short period Cepheid-strip star (V432 Oph), one is an eclipsing binary (AQ Boo), and one is of uncertain type (V351 Cyg). The stars we have observed as MR Her and TY Sge are the same ones which were identified on ...


Fabrication Of N-Type Nickel Doped B5 C1+Δ Homojunction And Heterojunction Diodes, Seong-Don Hwang, Ken Yang, Peter A. Dowben, Ahmad A. Ahmad, N.J. Ianno, J.Z. Li, J.Y. Lin, H.X. Jiang, D.N. Mcilroy Nov 1996

Fabrication Of N-Type Nickel Doped B5 C1+Δ Homojunction And Heterojunction Diodes, Seong-Don Hwang, Ken Yang, Peter A. Dowben, Ahmad A. Ahmad, N.J. Ianno, J.Z. Li, J.Y. Lin, H.X. Jiang, D.N. Mcilroy

Peter Dowben Publications

We have successfully nickel doped a boron carbide (B5C) alloy film. The nickel doped boron-carbide (Ni-B5C1+δ) thin films were fabricated from a single source carborane cage molecule and nickelocene [Ni(C5H5)2] using plasma enhanced chemical vapor deposition. Nickel doping transforms the highly resistive undoped film from a p-type material to an n-type material. This has been verified from the characteristics of diodes constructed of Ni-B5C1+δ on both n-type silicon and p-type B5C. The homojunction diodes exhibit excellent rectifying properties over a wide range of temperatures. ©1997 ...


Nanoscale Investigation Of Fatigue Effects In Pb(Zr,Ti)O3 Films, Alexei Gruverman, O. Auciello, H. Tokumoto Nov 1996

Nanoscale Investigation Of Fatigue Effects In Pb(Zr,Ti)O3 Films, Alexei Gruverman, O. Auciello, H. Tokumoto

Alexei Gruverman Publications

Scanning force microscopy has been used to perform a comparative nanoscale study of domain structures and switching behavior of Pb(ZrxTi1-x)O3 (PZT) thin films integrated into heterostructures with different electrodes. The study revealed a significant difference between polarization state of as-deposited PZT films on RuO2 and Pt electrodes. The PZT/RuO2 films exhibit polydomain crystallites and show almost symmetric switching behavior, while the PZT/Pt films are mainly in a single polarity state and exhibit highly asymmetric piezoelectric hysteresis loops. Formation of unswitchable polarization within the grains of submicron size as a result ...


Photoionization Of Atoms, Anthony F. Starace Nov 1996

Photoionization Of Atoms, Anthony F. Starace

Anthony F. Starace Publications

This chapter outlines the theory of atomic photoionization, and the dynamics of the photon-atom collision process. Those kinds of electron correlation that are most important in photoionization are emphasized, although many qualitative features can be understood within a central field model. The particle-hole type of electron correlations are discussed, as they are by far the most important for describing the single photoionization of atoms near ionization thresholds. Detailed reviews of atomic photoionization are presented in Refs. [I] and 121. Current activities and interests are well-described in two recent books [3,4]


Electron Energy Distributions From Multiple Ionization In 20–120-Kev H+ + Ar Collisions, Yang-Soo Chung, M. Eugene Rudd Nov 1996

Electron Energy Distributions From Multiple Ionization In 20–120-Kev H+ + Ar Collisions, Yang-Soo Chung, M. Eugene Rudd

M. Eugene Rudd Publications

Energy-analyzed secondary electrons from H+ + Ar collisions at eight proton energies from 20 to 120 keV were detected in coincidence with recoil ions of charge states 1–3. The charge states were distinguished by time-of-flight measurements and the electron energies were analyzed by a newly designed electrostatic analyzer of the low-pass high-pass filter type which has a large (~1.45π steradian) solid angle acceptance. For each of nine electron energies from 10 to 160 eV, the ionizing events associated with each residual ion charge state were counted. The electron energy dependence of the charge-state ratios and the average charge determined ...


Two-Center Effects In Ion-Atom Collisions: A Symposium In Honor Of M. Eugene Rudd, Lincoln, Ne May 1994 — Contents And Preface, Timothy J. Gay, Anthony F. Starace Oct 1996

Two-Center Effects In Ion-Atom Collisions: A Symposium In Honor Of M. Eugene Rudd, Lincoln, Ne May 1994 — Contents And Preface, Timothy J. Gay, Anthony F. Starace

Anthony F. Starace Publications

Following a distinguished career in atomic physics, sketched in the accompanying biography, M. Eugene Rudd retired From the faculty of the University of Nebraska in the spring of 1993. In order to celebrate his many research accomplishments, a two day scientific conference, held on 13-14 May 1994, was organized in Lincoln. It was felt that the special spirit that Rudd brought to the lab would be highlighted by a conference designed to analyze in detail a subject of current research in which he was a pioneer: two center-effects in ion-atom ionizing collisions.

Prior to 1980, primarily as a result of ...


Biographical Sketch Of M. Eugene Rudd, Robert Katz, Duane H. Jaecks Oct 1996

Biographical Sketch Of M. Eugene Rudd, Robert Katz, Duane H. Jaecks

Faculty Publications, Department of Physics and Astronomy

Dr. Rudd's research in atomic collision physics has been characterized by originality and thoroughness. He has written review articles and chapters in the Encyclopedia of Physics - and elsewhere, and is a co-author on a book on atomic collisions. He has published more than 75 refereed research papers, many of which were of seminal importance. He was the first to study systematically the dependence of the probability for electron emission in ion-atom collisions on the incident ion's energy, and on the ejected electron's energy and angle of emission. In 1964 he made the first experimental observation of doubly ...


A Novel Multilayer Circuit Process Using Yba2cu3ox /Srtio3 Thin Films, H.Q. Li, R.H. Ono, L.R. Vale, D.A. Rudman, Sy_Hwang Liou Oct 1996

A Novel Multilayer Circuit Process Using Yba2cu3ox /Srtio3 Thin Films, H.Q. Li, R.H. Ono, L.R. Vale, D.A. Rudman, Sy_Hwang Liou

Si-Hwang Liou Publications

A process combining hydrofluoric acid (HF) and Ar+ ion milling has been used to make YBa2Cu3Oχ/SrTiO3/YBa2Cu2Oχ (YBCO/STO/YBCO) multilayer test circuits. Low-angle steps can be readily etched in STO and YBCO films with this process. YBCO lines crossing 5° steps have about the same critical temperature Tc (89–90 K) and critical current density Jc (>1X106 A/cm2 at 86 K) as lines on planar surfaces. Via connections have the same Tc as other circuit components and adequate critical currents for ...


Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D. N. Mcilroy, Peter A. Dowben, E. Rühl Oct 1996

Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D. N. Mcilroy, Peter A. Dowben, E. Rühl

Peter Dowben Publications

Auger electron spectra and Auger yields of free argon clusm in the Ar(2p) excitation regime are reported. The Auger yield spectra show characteristic changes as a function of cluster size. The results indicate that the Auger yield signal originates primarily from the surface of the cluster. The results are compared to bulk-sensitive experimental techniques, such as total electron yields (TEY), zero kinetic energy electron (ZEKE) spectra for variable size clusters, as well as Auger yield spectra of condensed argon multilayers.


Current Status Of The Saddle-Point Model, Timothy J. Gay Oct 1996

Current Status Of The Saddle-Point Model, Timothy J. Gay

Timothy J. Gay Publications

The saddle-point model of ionizing ion-atom collisions is based on the idea that when a charged projectile ionizes target electrons. some of the ejected electrons find themselves on the transient, moving saddle-point of Coulomb potential with a velocity that matches that of the saddle point. Feeling no force at this position, they "ride" the saddle out of the collision volume and are thus ionized. In the case of the prototypical H+ + H system, or in any proton–neutral target collision, the saddle point moves at half the projectile velocity, so these electrons are often referred to as "v/2" electrons ...


Radial Dose Distributions In The Delta-Ray Theory Of Track Structure, Francis A. Cucinotta, Robert Katz, John W. Wilson, Rajendra R. Dubey Oct 1996

Radial Dose Distributions In The Delta-Ray Theory Of Track Structure, Francis A. Cucinotta, Robert Katz, John W. Wilson, Rajendra R. Dubey

Faculty Publications, Department of Physics and Astronomy

The radial dose distribution from delta rays, fundamental to the delta ray theory of track structure, is recalculated. We now include the model of Rudd for the secondary electron spectrum in proton collisions. We include the effects of electron transmission through matter and the angular dependence of secondary electron emission. Empirical formulas for electron range versus electron energy are intercompared in a wide variety of materials in order to extend the track structure theory to arbitrary media. Radial dose calculations for carbon, water, silicon, and gold are discussed. As in the past, effective charge is used to scale to heavier ...


Magnetic Neutron-Scattering Investigation Of The Field-Induced Griffiths Phase In Fecl2, Christian Binek, D. Bertrand, L.P. Regnault, Wolfgang Kleemann Oct 1996

Magnetic Neutron-Scattering Investigation Of The Field-Induced Griffiths Phase In Fecl2, Christian Binek, D. Bertrand, L.P. Regnault, Wolfgang Kleemann

Christian Binek Publications

Quasielastic neutron scattering has been utilized to investigate the Griffiths phase induced by an axial magnetic field in FeCl2 at temperatures Tc(H)⩽T⩽TN, where Tc(H) is the transition temperature in an external magnetic field H. We present the temperature dependence of the integrated neutron-scattering intensity at fixed scattering vectors for various magnetic fields. On cooling below TN the antiferromagnetic short-range fluctuations decrease due to an increase of the volume fraction which is already antiferromagnetically ordered. A weighted average of the local contributions to the antiferromagnetic susceptibility quantitatively describes the scattering cross section.


Effect Of Beam Attenuation On Photorefractive Grating Erasure, Martin M Liphardt, Arosha Goonesekera, Stephen Ducharme, James M. Takacs, Lei Zhang Oct 1996

Effect Of Beam Attenuation On Photorefractive Grating Erasure, Martin M Liphardt, Arosha Goonesekera, Stephen Ducharme, James M. Takacs, Lei Zhang

Stephen Ducharme Publications

We investigate the influence of attenuation on the speed of erasure of photorefractive gratings by solving the coupled-wave equations in the undepleted pump approximation and by taking into account the attenuation and Gaussian intensity profile of all the beams. The extrinsic grating decay rate is significantly lower than the intrinsic photorefractive decay rate in samples with overall attenuation as low as 10%. The Gaussian beam profiles of the readout and the erasing beams result in a further reduction of the extrinsic decay rate. The results of these calculations are used to determine the spectrum of intrinsic decay rates in a ...


Fundamental Aspects Of Atomic Photoionization With High-Brightness Light Sources, Anthony F. Starace, Steven T. Manson Sep 1996

Fundamental Aspects Of Atomic Photoionization With High-Brightness Light Sources, Anthony F. Starace, Steven T. Manson

Anthony F. Starace Publications

The construction of numerous new synchrotron light sources worldwide is providing the means to study atomic and molecular photoionization processes at a level of detail that is unparalleled in even the recent past. Correspondingly, in theory, the availability of supercomputers and, perhaps more important, relatively inexpensive computer workstations, has permitted theoretical calculations to tackle more complex processes than ever before. In short, these technical developments are creating an unprecedented amount of data to be analyzed and understood.

In this volume, many of the experimental and theoretical advances of recent years will be described. We take the point of view in ...


Is There Spin-Glass Exchange In Ultrathin Fe(110) Films ?, Ralph Skomski, D. Sander, Axel Enders, J. Kirschner Sep 1996

Is There Spin-Glass Exchange In Ultrathin Fe(110) Films ?, Ralph Skomski, D. Sander, Axel Enders, J. Kirschner

Ralph Skomski Publications

The magnetism of sesquilayer bcc iron films on W(110) is investigated. Coercivity data and theoretical calculations that the freezing of the magnetization at low temperatures reflects exchange-dominated domain-wall pinning rather than superparamagnetic spin-glass behavior.


High Coercivity Smfesic Films Fabricated By Multilayer Sputtering, S.Y. Zhang, Z.S. Shan, Yi Liu, David J. Sellmyer Sep 1996

High Coercivity Smfesic Films Fabricated By Multilayer Sputtering, S.Y. Zhang, Z.S. Shan, Yi Liu, David J. Sellmyer

David Sellmyer Publications

SmFeSiC thin films have been obtained by sputtering SmFe/C(Si) multilayers with a Ta underlayer on Si substrates and subsequently annealing at 700° C. The coercivity of the SmF films strongly depends on the sputtering and annealing conditions. The influence of the thickness of the Ta underlayer, the thickness ratio of SmFe to C(Si), the argon pressure and heat treatment In- plane Coercivities up to 7.2 kOe and squareness of 0.94 were obtained.


Magnetization Reversal Behavior In Cobalt Rare-Earth Thin Films, S.S. Malhotra, Z.S. Shan, D.C. Stafford, Sy_Hwang Liou, David J. Sellmyer Sep 1996

Magnetization Reversal Behavior In Cobalt Rare-Earth Thin Films, S.S. Malhotra, Z.S. Shan, D.C. Stafford, Sy_Hwang Liou, David J. Sellmyer

David Sellmyer Publications

Cobalt RareEarth (CoR, R = Pr,Sm) thin films on a Cr underlayer have shown promise as future ultra high density magnetic recording media. The activation volume or the magnetic switching volume (v*) is an important consideration for thermal stability and media noise in high density recording media and V* can also provide information about the magnetization reversal behavior in these films. The magnetic switching volume was estimated for the CoPr films with thicknesses from 28 to 639 nm with a Cr underlayer of 80 nm annealed at 500 0C. The measured switching volume ranges from 1.3 to 1 ...


Film Stress And Domain Wall Pinning In Sesquilayer Iron Films On W(110), D. Sander, Ralph Skomski, C. Schmidthals, Axel Enders, J. Kirschner Sep 1996

Film Stress And Domain Wall Pinning In Sesquilayer Iron Films On W(110), D. Sander, Ralph Skomski, C. Schmidthals, Axel Enders, J. Kirschner

Ralph Skomski Publications

We present an in situ investigation of the correlation between elastic and magnetic properties of monolayer iron films on W(110). Sesquilayers, consisting of two-monolayer patches on a nearly ideal monolayer film, exhibit anomalous elastic properties and a strikingly high in-plane coercivity of order 0.3 T. The sesquilayer coercivity maximum is explained by a novel domain wall pinning mechanism, based on an enhanced exchange interaction in the two monolayer thick patches. This rather unique behavior is restricted to (110) surfaces but does not occur on (100) and (111) thin films.


The Itinerant Limit Of Metallic Anisotropy, Ralph Skomski Sep 1996

The Itinerant Limit Of Metallic Anisotropy, Ralph Skomski

Ralph Skomski Publications

The anisotropy contribution of itinerant electrons confined to a quantum-well potential is calculated and compared with the quasi-ionic contribution due to virtually bound electrons. The easy magnetization direction of the non-L-S quantum-well electrons lies in the plane, and the magnitude of the anisotropy, maximally of order 10 J/m3, is too weak to explain anisotropies encountered in practice. This means that itinerant 3d anisotropy in bulk materials and thin films is associated with Hund's rules-type ionic Contributions.


Doubly Differential Cross Sections Of Low-Energy Electrons Emitted In The Ionization Of Molecular Hydrogen By Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, D. Ling, Y. D. Wang, C. D. Lin, R. Moshammer, G. W. Kerby Iii, M. W. Gealy, M. Eugene Rudd Sep 1996

Doubly Differential Cross Sections Of Low-Energy Electrons Emitted In The Ionization Of Molecular Hydrogen By Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, D. Ling, Y. D. Wang, C. D. Lin, R. Moshammer, G. W. Kerby Iii, M. W. Gealy, M. Eugene Rudd

M. Eugene Rudd Publications

We have measured the double differential cross sections (DDCS) (d2σ/dεedΩe) of low-energy electron emission in the ionization of H2 bombarded by bare carbon ions of energy 30 MeV. The energy and angular distributions of the electron DDCS have been obtained for 12 different emission angles and for electron energies varying between 0.1 and 300 eV. We have also deduced the single differential and total ionization cross section from the measured DDCS. The data have been compared with the predictions of first Born approximations and the CDW-EIS (continuum distorted wave–eikonal ...


High Coercive Field And Film Stress For Epitaxial Monolayers Of Fe On W(110), D. Sander, Axel Enders, Ralph Skomski, J. Kirschner Sep 1996

High Coercive Field And Film Stress For Epitaxial Monolayers Of Fe On W(110), D. Sander, Axel Enders, Ralph Skomski, J. Kirschner

Ralph Skomski Publications

Elastic and magnetic properties of ultra-thin iron films on tungsten(110) are investigated. In situ film stress measurements during growth show stress values of 25 GPa per deposited monolayer. Our experiments indicate that the tremendous film stress triggers the formation of a misfit dislocation network at a coverage of 1.5 monolayers. The effect of the film stress and its spatial variation on the magnetic behavior are discussed. We find an high coercivity of order 0.3 T for 1.5 monolayer thick films. A model is presented that explains the high coercivity in terms of strong domain wall pinning.


An Effective-Viscosity Description Of Domain-Wall Motion In Magnetic Thin Films With Perpendicular Anisotropy, Ralph Skomski, J. Giergiel, J. Kirschner Sep 1996

An Effective-Viscosity Description Of Domain-Wall Motion In Magnetic Thin Films With Perpendicular Anisotropy, Ralph Skomski, J. Giergiel, J. Kirschner

Ralph Skomski Publications

The expansion of magnetic domains in thin films with perpendicular anisotropy is investigated. To determine the domain-wall velocity as a function of the applied magnetic field a self-=consistent magnetic-viscosity approach is used. The main predictions of the theory are a linear behavior\r in the limit of moderately strong fields, a quasi-exponential behavior for fields close to the propagation field, and a negative velocity for very small and negative fields. The predictions of the theory are compatible with domain-wall investigations on Au/Co/Au sandwiches.


Determination Of Crystal-Field Parameters Of Sm2Fe17N3 And Sm2Fe17C3, S. Wirth, M. Wolf, K.H. Muller, Ralph Skomski, S. Brennan, J.M.D. Coey Sep 1996

Determination Of Crystal-Field Parameters Of Sm2Fe17N3 And Sm2Fe17C3, S. Wirth, M. Wolf, K.H. Muller, Ralph Skomski, S. Brennan, J.M.D. Coey

Ralph Skomski Publications

The crystal-field parameters A20 and A40 were determined from the magnetocrystalline anisotropy constants K1 and K2 in a linear approximation for Sm2Fe17Zx (Z = N, C) compounds. For the materials investigated, the values of Iη0 are calculated in two ways: i) from the Kί at zero temperature and ii) from the temperature dependence of the Kί. Both methods give equivalent results. The value A20≈-400 Ka0-2 has been obtained which corresponds to an inverse THOMAS-FERMI screening length q≈2.3 Å-1 calculated within the framework ...


Lorentz Microscopy Observation Of Magnetic Grains In Co-Sm // Cr Films, Yi Liu, Z.S. Shan, David J. Sellmyer Sep 1996

Lorentz Microscopy Observation Of Magnetic Grains In Co-Sm // Cr Films, Yi Liu, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

This paper presents our recent Lorentz microscopy study of magnetic domain structure and its relation to the nanostructure of Co-Sm films. The magnetic domains were imaged by Foucault Lorentz mode and the corresponding nanostructure was revealed by bright field and high resolution images. The nanostructure is composed of clusters of 20 nm grown on Cr grains. Each cluster is formed by the amorphous matrix and about 5 nm crystallites distributed in the matrix. It is found that each cluster forms a magnetic grain. Such magnetic grains show uniform contrast near the magnetic domain wall, and correspond to the switching volume ...