scholarly journals Анизотропия отрицательного магнетосопротивления в эапитаксиальных слоях GaMnAs

2021 ◽  
Vol 55 (2) ◽  
pp. 159
Author(s):  
А.С. Газизулина ◽  
А.А. Насиров ◽  
А.А. Небесный ◽  
П.Б. Парчинский ◽  
Dojin Kim
Keyword(s):  
Uniaxial Anisotropy ◽  
Ferromagnetic State ◽  
Negative Magnetoresistance ◽  
Epitaxial Layers ◽  
Axis Orientation ◽  
Hard Axis ◽  
Spatially Oriented ◽  
Gamnas Layer

Anisotropy of magnetotransport properties of GaMnAs epitaxial layers in ferromagnetic state has been investigated as a function of temperature. The anisotropy of negative magnetoresistance that is not related to uniaxial anisotropy and hard axis orientation has been observed. This anisotropy may be result of arising of spatially oriented structures in the GaMnAs layer during its growth.

scholarly journals Dynamics of Magnetization in Multilayer TbCo / FeCo Structures under the Influence of Femtosecond Optical Excitation

2019 ◽  
Vol 7 (3) ◽  
pp. 50-58 ◽  
Author(s):  
N. A. Ilyin ◽  
A. A. Klimov ◽  
N. Tiercelin ◽  
P. Pernod ◽  
E. D. Mishina ◽  
...  
Keyword(s):  
Easy Axis ◽  
Uniaxial Anisotropy ◽  
Anisotropy Field ◽  
Optical Excitation ◽  
Spin Precession ◽  
Heat Diffusion ◽  
Easy Magnetization ◽  
Test Beam ◽  
Magnetic Subsystem ◽  
Hard Axis

The need to study ultrafast processes in magnetism is due to the prospects for creating ultrafast magnetic recording and ultrafast spintronic devices. In order to excite the magnetic subsystem femtosecond optical pulses are used. The excitement is manifested as in spin precession. In metals, the material is heated first due to significant optical absorption, and significant Joule losses occur. The most important task is to search for materials in which spin processes are excited without heating. Obvious candidates are weakly absorbing materials, such as ferrite garnets. However, the range of such materials and the range of their functionality are limited.The purpose of this work is to study the dynamics of systems with nonthermal mechanisms of spin precession excitation. Such excitation is possible in ferromagnetic / antiferromagnetic heterostructures with exchange interaction, provided that the recombination time of photocarriers is shorter than the time of heat diffusion. Multilayer TbCo / FeCo structures of the near IR range were investigated for a femtosecond optical pulse. The spin dynamics are compared with the direction of the wave vector of the exciting pulse along and perpendicular to the axis of easy magnetization of the structures (“easy axis” and “hard axis” geometry, respectively). It is shown that in case of “easy axis” geometry the determinative mechanism is the thermal interaction. When the system is exposed to an excitation pulse, this mechanism leads to a decrease in the projection of magnetization on the direction of propagation of the test beam. In case of “hard axis” geometry, the magnetization turns to the magnetic field at the initial stage. Then it precesses and relaxes to an equilibrium angular orientation. Such dynamics indicate a rapid recovery of the uniaxial anisotropy field after laser irradiation. The presented results demonstrate an ultrafast change in the magnetic anisotropy induced during the fabrication of the heterostructure under study, which may be of interest for optical control of the orientation of the magnetization.

scholarly journals Microstructures and Soft Magnetic Properties of High Saturation Magnetization Fe-Co-N alloy Thin Films

2000 ◽  
Vol 614 ◽  
Author(s):  
N. X. Sun ◽  
S. X. Wang ◽  
Chin-Ya Hung ◽  
Chester X. Chien ◽  
Hua-Ching Tong
Keyword(s):  
Saturation Magnetization ◽  
Easy Axis ◽  
Uniaxial Anisotropy ◽  
Single Layer ◽  
Soft Magnetic Materials ◽  
High Saturation Magnetization ◽  
Soft Magnetic ◽  
Hard Axis ◽  
High Saturation ◽  
Significant Difference

ABSTRACTHigh saturation magnetization soft magnetic materials are required for future high-density recording heads as well as high frequency inductors. In this work, (Fe0.7Co0.3)1−xNx (or in short FeCoN) alloy films were synthesized with a high saturation magnetization of 24.5 kG, a hard axis coercivity of 5 Oe, an easy axis coercivity of 18 Oe, and a resistivity of 55 μΩcm. The FeCoN film sandwiched between two permalloy layers (5 nm) shows very good magnetic softness, a low hard axis coercivity of 0.6 Oe, an easy axis coercivity of 7.8 Oe, an excellent in-plane uniaxial anisotropy with an anisotropy of about 20 Oe, an initial permeability of 1000, and a roll-off frequency of 1.5 GHz. In order to understand the effect of the permalloy layers on the FeCoN layer, we fabricated four film structures: single layer FeCoN film; FeCoN film sandwiched between two permalloy layers on both sides; FeCoN film with one permalloy layer as the underlayer; and FeCoN film with one permalloy layer as caplayer. All these film structures were both magnetically and structurally characterized and compared. Structural characterization shows that there is no significant difference in the grain size of the FeCoN single layer and the FeCoN layer sandwiched between two permalloy layers. The four film structures have almost the same amount of compressive stress, about −300 MPa; and their saturation magnetostriction constants are also very close, in the range of 39.6×10−6 to 44.3×10−6. Difference in the crystallographic textures was observed in the pole figures for the FeCoN single layer and FeCoN film with permalloy underlayer.

HOPPING MAGNETOTRANSPORT IN THE δ-DOPING LAYER

1994 ◽  
Vol 08 (07) ◽  
pp. 789-800 ◽  
Author(s):  
F. Koch
Keyword(s):  
Molecular Beam Epitaxy ◽  
Magnetic Flux ◽  
Molecular Beam ◽  
Negative Magnetoresistance ◽  
Epitaxial Layers ◽  
Interference Effects ◽  
Hopping Transport ◽  
Coherent Superposition ◽  
Planar Arrays

We review the observations on hopping transport in planar arrays of Si donor atoms in GaAs epitaxial layers grown by molecular beam epitaxy. It is shown that properly designed δ-doping layers permit one to unambigously identify interference effects that result from the coherent superposition of the tunneling amplitudes along alternative paths in the plane. Magnetic flux through the area generated by the paths destroys the interference and leads to negative magnetoresistance. We discuss the observed non-monotonic variation of the resistance.

Thermal behavior of hard-axis magnetization in noninteracting particles with uniaxial anisotropy

2009 ◽  
Vol 95 (20) ◽  
pp. 202503 ◽  
Author(s):  
F. Ilievski ◽  
A. Cuchillo ◽  
W. Nunes ◽  
M. Knobel ◽  
C. A. Ross ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Uniaxial Anisotropy ◽  
Hard Axis

Anisotropy of Negative Magnetoresistance in GaMnAs Epitaxial Layers

2021 ◽  
Vol 55 (2) ◽  
pp. 214-218
Author(s):  
A. S. Gazizulina ◽  
A. A. Nasirov ◽  
A. A. Nebesniy ◽  
P. B. Parchinskiy ◽  
Dojin Kim
Keyword(s):  
Negative Magnetoresistance ◽  
Epitaxial Layers

The Impact of Pregrowth Conditions and Substrate Polytype on SiC Epitaxial Layer Morphology

1996 ◽  
Vol 423 ◽  
Author(s):  
A. A. Burk ◽  
L. B. Rowland ◽  
G. Augustine ◽  
H. M. Hobgood ◽  
R. H. Hopkins
Keyword(s):  
Epitaxial Layer ◽  
Substrate Surface ◽  
Surface Preparation ◽  
Growth Conditions ◽  
Epitaxial Layers ◽  
Axis Orientation ◽  
Step Flow ◽  
Morphological Defects ◽  
Step Flow Growth ◽  
The Impact

Abstract4H and 6H-SiC epitaxial layers exhibit characteristic morphological defects caused by process and substrate interferences with the a-axis directed step-flow growth. 4H-SiC is shown to typically exhibit worse morphology than 6H-SiC for a given off-axis orientation. SiC epitaxial layer defects are significantly reduced by the optimization of growth conditions and substrate surface preparation. The remaining highly variable defects are shown to emanate from the substrate surface with densities of ≥1000 cm−2

scholarly journals Transverse susceptibility of nickel thin films with uniaxial anisotropy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Scott A. Mathews ◽  
Christopher Musi ◽  
Nicholas Charipar
Keyword(s):  
Applied Field ◽  
Magnetic State ◽  
Uniaxial Anisotropy ◽  
Simulated Data ◽  
Anisotropy Field ◽  
Absolute Value ◽  
Hard Axis ◽  
Nickel Thin Films ◽  
Low Temperature Annealing ◽  
Theoretical Predictions

AbstractA finite temperature Stoner–Wohlfarth model has been used to calculate the transverse susceptibility of an ensemble of ferromagnetic particles with distributed anisotropy. The simulated transverse susceptibility is in excellent agreement with data acquired from thin film samples of elemental nickel, deposited on 128° Y-cut LiNb03. A strong, well-defined, uniaxial anisotropy is induced in the nickel film by low temperature annealing. Three peaks in the transverse susceptibility are observed in both the measured and simulated data when the applied field is misaligned with the hard axis by a few degrees. Two broad, reversible peaks occur when the applied field is equal to the anisotropy field. A single, sharp irreversible peak occurs when the absolute value of the applied field is less than the anisotropy field, and is associated with a metastable magnetic state. The irreversible peak disappears when the applied field is well aligned with the hard axis. The observed transverse susceptibility is consistent with the theoretical predictions of Aharoni et al. and is therefore consistent with the Stoner–Wohlfarth model.

Crystal Structure Determination of Glycerol-Containing Lipids from Electron Diffraction Data. Use of Analog Compounds Based upon Configurational Isomers of Cyclopentane-1, 2, 3-TRIOL

1977 ◽  
Vol 35 ◽  
pp. 24-25
Author(s):  
Douglas L. Dorset ◽  
Anthony J. Hancock
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Surface ◽  
Coherent Scattering ◽  
Crystal Structure Determination ◽  
Electron Diffraction Data ◽  
Polar Group ◽  
Axis Orientation

Lipids containing long polymethylene chains were among the first compounds subjected to electron diffraction structure analysis. It was only recently realized, however, that various distortions of thin lipid microcrystal plates, e.g. bends, polar group and methyl end plane disorders, etc. (1-3), restrict coherent scattering to the methylene subcell alone, particularly if undistorted molecular layers have well-defined end planes. Thus, ab initio crystal structure determination on a given single uncharacterized natural lipid using electron diffraction data can only hope to identify the subcell packing and the chain axis orientation with respect to the crystal surface. In lipids based on glycerol, for example, conformations of long chains and polar groups about the C-C bonds of this moiety still would remain unknown.One possible means of surmounting this difficulty is to investigate structural analogs of the material of interest in conjunction with the natural compound itself. Suitable analogs to the glycerol lipids are compounds based on the three configurational isomers of cyclopentane-1,2,3-triol shown in Fig. 1, in which three rotameric forms of the natural glycerol derivatives are fixed by the ring structure (4-7).

Transmission Electron Microscopy Studies of Aluminum Oxidation

1985 ◽  
Vol 43 ◽  
pp. 268-269
Author(s):  
J.Y. Lee
Keyword(s):  
Nucleation And Growth ◽  
Ion Milling ◽  
Cross Sectional ◽  
Polycrystalline Aluminum ◽  
Axis Orientation ◽  
Temperature Oxidation ◽  
Aluminum Oxidation ◽  
Transmission Electron ◽  
High Resolution Images ◽  
Argon Ion

In the oxidation of metals and alloys, microstructural features at the atomic level play an important role in the nucleation and growth of the oxide, but little is known about the atomic mechanisms of high temperature oxidation. The present paper describes current progress on crystallographic aspects of aluminum oxidation. The 99.999% pure, polycrystalline aluminum was chemically polished and oxidized in 1 atm air at either 550°C or 600°C for times from 0.5 hr to 4 weeks. Cross-sectional specimens were prepared by forming a sandwich with epoxy, followed by mechanical polishing and then argon ion milling. High resolution images were recorded in a <110>oxide zone-axis orientation with a JE0L JEM 200CX microscope operated at 200 keV.

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