bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carrier-Concentration-Dependent Magnetic Properties of the Diluted Magnetic Semiconductor SnMnte
Authors: Swagten H. J. M. , Eltink S. J. E. A. , De Jonge W. J. M. 
Published: September 2012

ABSTRACTIn this paper experimental evidence is presented for the carrier concentration dependence of the magnetic properties of Sn0.97Mn0.03Te, yielding a critical concentration above which ferromagnetic interactions are dominant. The observed behavior can be fairly well explained within a modified RKKY-model. Preliminary experiments on the low temperature magnetic phases indicate re-entrant spinglass behavior, which is qualitatively described with the spinglass model of Sherrington and Kirkpatrick.
In-Situ Techniques for Studying Epitaxially Grown Layers and Determining their Magnetic Properties
Authors: Heinrich B. , Arrott A. S. , Cochran J. F. , Urquhart K. B. , Myrtle K. , Celinski Z. , Zhong Q. M. 
Published: September 2012

ABSTRACTUltrathin films of bcc Fe (001) on Ag (001) and Fe/Ni (001) bilayers on Ag were grown by molecular beam epitaxy. A wide range of surface science tools (RHEED, REELFS, AES, and XPS) were employed to establish the quality of epitaxial growth. Ferromagnetic resonance and Brillouin light scattering were used to extract the magnetic properties. Emphasis was placed on the study of magnetic anisotropies. Large uniaxial anisotropies with the easy axis perpendicular to the film surface were observed in all ultrathin structures studied. In sufficiently thin samples the saturation magnetization was oriented perpendicular to the film surface in the absence of an applied field. It has been demonstrated that in bcc Fe films the uniaxial perpendicular anisotropy originates at the film interfaces. Fe/Ni bilayers were also investigated. Ni grows in the pure bcc structure for the first 3–6ML and then transforms to a new structure which exhibits unique magnetic properties. Transformed ultrathin bilayers possesses large in-plane 4th order anisotropies far surpassing those observed in bulk Fe and Ni. The large 4th order anisotropies originate in crystallographic defects formed during the Ni lattice transformation.
Characterization of Epitaxial Fe on GaAs(110) by Scanning Tunneling Microscopy
Authors: Dragoset R. A. , First P. N. , Stroscio Joseph A. , Pierce D. T. , Celotta R. J. 
Published: September 2012

ABSTRACTIron on GaAs(110) comprises an interesting system not only due to small lattice mismatch, 1.4%, but also because of the magnetic properties of the overlayer. In the present work, scanning tunneling microscopy (STM) was used to investigate bcc Fe films in the 0.1 Å to 20 Å thickness range, grown at 300 K and 450 K substrate temperatures. STM images show Volmer-Weber growth with the formation of 3-D Fe islands 20–30 Å in diameter for 0.1–1 Å deposition at 300 K, increasing to 40–50 Å for thicker films. Iron island sizes at low coverage and thin film roughness at higher coverages both show significant dependence upon growth temperature.
Structural and Magnetic Characterization of Rare Earth and Transition Metal Films Grown on Epitaxial Buffer Films on Semiconductor
Authors: Farrow R. F. C. , Parkin S. S. P. , Speriosu V. S. , Bezinge A. , Segmuller A. P. 
Published: September 2012

ABSTRACTStructural and magnetic data are presented and discussed for epitaxial films of rare earth metals ( Dy, Ho, Er) on LaF3 films on the GaAs(TTT) surface and Fe on Ag films on the GaAs(001) surface. Both systems exhibit unusual structural characteristics which influence the magnetic properties of the metal films. In the case of rare earth epitaxy on LaF3 we present evidence for epitaxy across an incommensurate or discommensurate interface. Coherency strain is not transmitted into the metal which behaves much like bulk crystals of the rare earths. In the case of Fe films , tilted epitaxy and long-range coherency strain are confirmed by X-ray diffractometry. Methods of controlling some of these structural effects by modifying the epitaxial structures are presented.
Magnetic Domains in Epitaxial (100) Fe Thin Films
Authors: Florczak Jeffrey M. , Ryan P. J. , Kuznia J. N. , Wowchak A. M. , Cohen P. I. , White R. M. , Prinz G. A. , Dahlberg E. Dan 
Published: September 2012

ABSTRACTBy use of Kerr microscopy, the domain patterns of thin Fe films (10 nm) grown on Inx Ga1-x As (0.09 ≤ x ≤ 0.25)/GaAs substrates have been investigated. For This nvestigation, two types of InGaAs buffer layers were prepared. One consisted of a single, thick InGaAs layer and the second composed of an InGaAs strained layer superlattice. Both were grown on (100) GaAs substrates. The study showed that many of the domain walls were approximately parallel to the easy axis of Fe for those films grown on the low x alloy, e.g. x-0.1, InGaAs buffer layers. In the alloy films with larger values of x, e.g. x-0.2, the domain pattern of the Fe overlayer was strongly influenced by dislocations of the strain relieved InGaAs buffer layer. These dislocations manifested themselves as corrugations parallel to the <110> directions in the InGaAs. Kerr microscopy of a x-0.2 film indicated the presence of long, narrow domains with their long axes parallel to the striations. Although shape anisotropy arguments predicted that the magnetization should be parallel to the striations, magnetometer data indicated that a substantial component of magnetization was oriented perpendicular to the corrugations at low fields. The Fe film grown on the superlattice had magnetic domains very similar to a thick Fe film (0.5 μm) grown on GaAs.
X-Ray Scattering Studies of Thin Films and Multilayers
Authors: Cargill G. S. 
Published: September 2012

ABSTRACTX-ray scattering experiments provide important information about the atomic scale structure and the microstructure of thin films and multilayers. The high intensity, brightness, and broad energy spectrum of synchrotron radiation greatly extend capabilities of scattering experiments, particularly for scattering from ultrathin films and for anomalous dispersion scattering from alloys. Examples of scattering studies of both crystalline and amorphous materials are given in this overview.
Ferromagnetic and Nuclear Magnetic Resonance Study of Co/Pd Multilayers
Authors: Gronckel H. A. M. De , Swuste C. H. W. , Kopinga K. , Jonge W. J. M. De 
Published: September 2012

ABSTRACTThe microscopic properties of Co/Pd multilayers were studied by ferromagnetic and nuclear magnetic resonance. In addition to previous results the magnetic anisotropy is found to be also a function of the Pd layer thickness, increasing below 20 Å for decreasing thickness. This is ascribed to a decrease in the Pd/Co interface contribution to the anisotropy.Hyperfine field spectra show a shift to lower hyperfine fields upon decreasing Co sublayer thickness. This is attributed to an expansion of the Co ‘lattice’. Comparison of the results on the [111] multilayers with those on almost single phased [100] multilayers suggests that this expansion is nearly isotropic.
Exafs Study of the Stability of Amorphous TbFe Thin Films
Authors: Samant Mahesh G. , Marinero Ernesto E. , Robinson Clifford , Cargill G. S. 
Published: September 2012

ABSTRACTEXAFS is used to measure the local atomic structure of Fe in Au doped Tb-Fe thin film alloys. The as deposited sample shows structural fcatures which are essentially identical to those of the undoped films. Au additions stabilizes the amorphous structure against recrystallization, however, the loss of magnetic anisotropy under thermal annealing is not reduced. This demonstrates that magnetic relaxation in these alloys does not involve crystallization of the amorphous structure.
Hrem Structural Studies of TbFeCo Thin Films
Authors: Li Z. G. , Smith David J. , Sickafus K. 
Published: September 2012

ABSTRACTThe microstructure of TbFeCo thin films prepared under different deposition conditions has been observed in crosssection and top-view using high-resolution electron microscopy, as well as conventional bright-field and dark-field techniques. A comparison has been made with FeCo thin films prepared under identical experimental conditions. Very fine microcrystals (sizes 2–5nm) were observed in the basically amorphous TbFeCo thin films whereas much larger crystals (sizes 20–50nm) were visible in the primarily crystalline FeCo thin films. It was also found that the size of the nanocrystals in the TbFeCo films depended upon the argon partial pressure during deposition.
Time-Dependent Landau-Ginzburg Modelling of Magnetic Inhomogeneities and Spiral Domain Structures in Thin Films
Authors: Tuszyński J. A. 
Published: September 2012

ABSTRACTA Landau-Ginzburg model for a uniaxial ferromagnetic thin film is presented which includes inhomogeneities due to nearest neighbor exchange interactions. The role of external magnetic fields is studied in the determination of exact symmetries of the equation of state. Spiral domain structures allowed by symmetry considerations as exact solutions at the critical and tricritical points have recently been found experimentally in epitaxially grown single-crystal garnet ferrite films. These experiments are discussed from the point of view of our model.
Exchange Anisotropy in Amorphous/Microcrystalline Co-Gd Films
Authors: Toxen A. M. , Hopkins A. , Hagstrom S. B. , White R. M. 
Published: September 2012

ABSTRACTMagnetization, TEM, and x-ray diffraction studies have been carried out on GdCox films sputtered onto Si or sapphire substrates at ˜90 C, ambient temperature. The composition range studied was x=2−8.5. Over the composition range defined approximately by 5>×>3, the films, which are 1–3 microns thick, exhibit a unidirectionally displaced B-H loop, characteristic of an exchange-biased phase. TEM studies indicated that the samples with the shifted loops indeed consist of a mixture of amorphous and microcrystalline phases. The characteristic size of the microstructure is 10–20 A. Electron diffraction shows a very broad ring characteristic of amorphous phase together with six or seven sharper rings characteristic of crystalline material which index best to the hexagonal GdCo5 structure or to a high temperature hexagonal Gd2Co17 phase. The diffraction pattern remains virtually unchanged over the composition range x=2–8. This leads us to conclude that the microcrystalline material consists of one, or perhaps more than one, metastable phase over the indicated composition range. X-ray diffraction shows only one broad maximum.
X-Ray Diffraction Study of Rare Earth Epitaxial Structures Grown by MBE onto (111) GaAs
Authors: Bennett W. R. , Farrow R. F. C. , Parkin S. S. P. , Marinero E. E. 
Published: September 2012

ABSTRACTWe report on the new epitaxial system LaF3/Er/Dy/Er/LaF3/GaAs (111) grown by molecular beam epitaxy. X-ray diffraction studies have been used to determine the epitaxial relationships between the rare earths, the LaF3 and the substrate. Further studies of symmetric and asymmetric reflections yielded the in-plane and perpendicular strain components of the rare earth layers. Such systems may be used to probe the effects of magnetoelastic interactions and dimensionality on magnetic ordering in rare earth metal films and multilayers.
Magnetic and Crystallographic Interactions of Alternately Deposited Fe and Al ultra-thin Layers
Authors: Nagakubo M. , Yamamoto T. , Naoe M. 
Published: September 2012

ABSTRACTMultilayered films consisting of ferromagnetic Fe and nonmagnetic Al layers were prepared by using ion beam sputtering, and the relationships between their crystallographic characteristics and soft magnetic properties have been investigated in detail.The periodicity of the multilayered films was confirmed for various layer thicknesses (ΔFe and ΔA1) above 10Å from their X-ray diffraction peaks at low angle. When ΔFe decreased along with ΔA1 from 100Å, the coercivity Hc decreased and showed a minimum of 1.5 Oe at layer thicknesses of 20Å, but at the same time, the saturation magnetization 4πMs which was estimated from total thickness of the Fe layers decreased from 20 kG and showed drastic decrease at ΔFe below 10Å. For ΔFe above 100Å, 4πMs was constant around 20 kG without dependence on ΔA1. When ΔAl was changed for AFe of 100Å, the values of Hc had a interesting relationship with the crystallite orientation in Fe layers. Namely, the preferentially oriented planes of α-Fe crystallites changed from (110) to (200) in the case of Al layer thinner than 15Å and Hc showed a minimum below 4 Oe for ΔAl in this transition range of crystallite orientation, while 4πMs of all Fe layers themselves was kept at 20 kG. Taking into consideration that the nearest atomic distance of fcc Al and the lattice constant of bcc Fe is almost the same, these results may be caused by crystallographical interaction at the interfaces between Fe and Al layers.
Calculation of Magnetization Processes in Multilayers with Antiferromagnetic Coupling between Adjacent Layers
Authors: Dieny B. , Gavigan J. P. , Rebouillat J. P. 
Published: September 2012

ABSTRACTThis paper presents calculations of hysteresis loops in ferromagnetic multilayer systems of cubic or uniaxial anisotropy with antiferromagnetic coupling between adjacent layers. The case of a bilayer has been systematically studied as a function of the strenght of the anisotropy. The two limiting cases corresponding to either a coherent rotation of the magnetization or to a non-dissipative nucleation-propagation mechanism are investigated. The influence of the number of layers is also discussed.
Giant Magnetoresistance of (001) Fe / (001) Cr Superlattices
Authors: Barthelemy A. , Baibich M. N. , Broto J. M. , Cabanel R. , Creuzet G. , Etienne P. , Fert A. , Friederich A. , Lequien S. , Dau F. Nguyen Van , Ounadjela K. 
Published: September 2012

ABSTRACTWe recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices grown by MBE. The magnetoresistance is found to be very large for thin Cr layers. We ascribe this magnetoresistance to a magnetic gate effect.We recently reported the observation of a very large magnetoresistance in (001)Fe/(001)Cr superlattices with thin Cr layers [1]. A large magnetoresitance has also been observed in Fe/Cr/Fe sandwhiches [2]. In both cases, for Cr layers thinner than about 30 Å an antiparallel coupling of the magnetization of neighbor Fe layers is indicated by magnetic, magneto-optic and light scattering measurements [1–3]. It thus turns out that the large magnetoresistance os associated with the change to parallel alignment in an applied field. In this paper, we present new data on the magnetic and transport properties of Fe/Cr superlattics and we concentrate on the discussion of the microscopic origin of the magnetoresistance
Spin Polarized Inverse Photoemission Study of Fe and Co Thin Films on W(001)
Authors: Cai Qing , Avci Recep , Lapeyre Gerald J. 
Published: September 2012

ABSTRACTSpin- (and angle-) resolved inverse photoemission spectroscopy (SPIPES) has beenused for studying magnetic thin films. The spin dependence of the unoccupiedelectronic structure has been investigated for in-situ-grown epitaxial, ultrathin Fe and Cofilms on W(001). The Fe overlayers have a square lattice and exhibit in-plane magneticremanence in the direction of the surface Brilluoin zone. Four or more atomic layersof Fe show bulklike SPIPES spectra with a majority spin peak at the Fermi energy (EF)and a broad minority peak 1.3 eV above EF The Co overlayers on W(001) showdistorted hexagonal structures in the plane with an atomic density twice that of theW(001) plane. Two atomic layers of Co show strong in-plane magnetic remanence withthe minority peak at 0.7 eV. The SPIPES results in general are consistent with thetheoretical electronic structure for momentum-conserving radiative transition from freeelectron-like bands down to the unoccupied 3d bands.
Magnetometry in Ultrathin Films using Spin Polarized Cascade Electrons
Authors: Kay Eric 
Published: September 2012

ABSTRACTIn this review, we show how spin polarized cascade electron spectroscopy provides a relatively rapid and flexible approach to the study of a variety of problems of current interest in both ultrathin magnetic films and surface magnetism. Specific examples relating to the non-bulk like magnetization behavior as a function of temperature of ultrathin films are given which lead to the conclusion that stabilization of the magnetization at low temperature is a universal characteristic of ultrathin magnetic films. Comparison between ultrathin film and surface magnetic behavior is made. Evidence is given that the weakening of exchange coupling both at the surface of a bulk sample and across magnetic spacer layers between an ultrathin magnetic thin film and a bulk sample can be evaluated and dramatic effects due to minute quantities of non-magnetic nearest neighbors are demonstrated.
Magnetic Properties of Rare-Earth/Fe Multilayered Films with Artificial Superstructures
Authors: Shinjo Teruya , Mibu Ko , Ogawa Shinichi , Hosoito Nobuyoshi 
Published: September 2012

ABSTRACTBy using UHV deposition technique, multilayered films consisting of Fe and rare-earth (Dy, Nd or Y) layers were prepared. Magnetic properties of Fe layers were investigated from 57Fe Mössbauer spectroscopy. From SQUID magnetic measurements, the behavior of rare-earth layers was studied. In Fe/Dy and Fe/Nd multilayers, there often exists a large perpendicular anisotropy. Mössbauer spectra evidenced that, in certain samples, the magnetization changes the direction, from in-plane at high temperature to perpendicular at low temperature. The origin of the perpendicular anisotropy is attributed to interface rare-earth atoms which are magnetically coupled with ferromagnetic Fe layers even at higher than their bulk Curie temperatures.
The Thermal Stability of Heavily Carbon-Doped GaAs Grown by Metalorganic Molecular Beam Epitaxy
Authors: Sohn Hyunchul , Weber E. R. , Nozaki S. , Konagai M. , Takahashi K. 
Published: September 2012

ABSTRACTHeavily carbon-doped GaAs thin films with a hole concentration of 5.8 × 1020 cm-3, grown by metalorganic molecular beam epitaxy (MOMBE), were annealed at 900°C for 30 minutes. The microstructural changes due to annealing were investigated by transmission electron microscopy. Electron diffraction study showed some evidence of carbon clustering on {111} in as-grown samples. A high density of precipitates was found in the annealed sample, together with a decrease of the lattice contraction and hole concentration. In the as-grown layer, misfit dislocations with only one type of Burgers vector were observed, while misfit dislocations with the several Burgers vectors were observed in [110] direction after annealing. The density of misfit dislocations in both <110> directions increased significantly even though the lattice contraction in carbon-doped GaAs decreased after annealing. A model is proposed to explain the change of misfit dislocation density in heavily carbon-doped GaAs layer.
Oxygen Related Lattice Defects in Silicon: Present Status
Authors: Bender Hugo , Vanhellemont Jan 
Published: September 2012

ABSTRACTThe structural characterization of the oxygen related lattice defects formed under different thermal cycling conditions is discussed. The present understanding on the nature of rod-like defects and oxide precipitates is reviewed. Attention is given to the whole lattice defect spectrum which is induced by the oxygen precipitation. The influence of carbon and dopants on the defects is discussed.
High Resistivity GaSb and GaAs Produced by MBE Growth at Elevated Temperatures
Authors: Polyakov A. Y. , Milnes A. G. , Stam M. , Wilson R. G. , Fang Z. Q. , Rai-Choudhury P. , Hillard R. J. 
Published: September 2012

ABSTRACTIn this paper we show that when grown by MBE at unusually high temperatures epitaxial layers of GaSb and GaAs are semi-insulating. In GaSb combination of Hall effect, TSC, SIMS and two probe resistivity profiling leads us to believe that high resistivity is due to production of midgap centers at elevated temperatures. No strong evidence of the prevalence of such midgap centers was obtained for high temperature GaAs layers and in this case we believe that high resistivity is associated with the formation of Ga-related precipitates acting as internal Schottky barriers.
Defect Structures in Heteroepitaxial InAs/GaAs and GaAs/InAs Grown by Atomic Layer Molecular Beam Epitaxy
Authors: Molina S. I. , Aragon G. , Garcia R. 
Published: September 2012

ABSTRACTA Transmission Electron Microscopy (TEM) study on ALMBE grown InAs/GaAs (001) is presented. The density and the types of defects contained in InAs and GaAs layers are clearly different. A relation between the planar defects in these layers and the compressive and extensive nature of the growth for each layer is found. Atomic Layer Molecular Beam Epitaxy (ALMBE) grown InAs layers possess a better quality of defects than other InAs layers grown on GaAs (001) by conventional MBE. Several ways of nucleation are presented as possible for explaining the existence of the different defects found in the studied heterostructure.
Effect of Electron Irradiation and Excess Cd on Ion-Assisted Doping of p-CdTe Thin Films
Authors: Kim D. , Fahrenbruch A. L. , Lopez-Otero A. , Bube R. H. 
Published: September 2012

ABSTRACTIon-assisted doping of homoepitaxial p-CdTe films with low energy P ions (20 eV) deposited by vacuum evaporation has been investigated. In order to control the properties of the films, we applied low energy electron irradiation and Cd overpressure during the growth. We report the results of measurements of hole density, spectral response of Cr/p-CdTe Schottky barriers (to estimate the minority carrier diffusion length Lj). From Ld, we have found that the quality of the films is dependent on both the ion dose and the ion energy. By reducing the ion energy to 20 eV and applying electron irradiation and Cd overpressure, p-CdTe films with p = 1 × 10 17 cm−3 and Lp =0.35 μm were obtained. A p-CdTe film with p = 1016 cm−3 was obtained with a low ion energy of 10eV.