Pure spin currents provide the possibility to control the magnetization state of conducting and insulating magnetic materials. They allow one to increase or reduce the density of magnons, and achieve ...coherent dynamic states of magnetization reminiscent of the Bose-Einstein condensation. However, until now there was no direct evidence that the state of the magnon gas subjected to spin current can be treated thermodynamically. Here, we show experimentally that the spin current generated by the spin-Hall effect drives the magnon gas into a quasi-equilibrium state that can be described by the Bose-Einstein statistics. The magnon population function is characterized either by an increased effective chemical potential or by a reduced effective temperature, depending on the spin current polarization. In the former case, the chemical potential can closely approach, at large driving currents, the lowest-energy magnon state, indicating the possibility of spin current-driven Bose-Einstein condensation.
A new approach to describing the magnetic properties of FeRh alloys is proposed. It is based on two assumptions about the properties of 3
d
and 4
d
electrons in these alloys. The first is the ...assumption that the 4
d
band is submerged under the Fermi level to a depth that ensures its complete filling at a temperature
T
= 0 K. The second is the assumption that there are two different spatial distributions of 3
d
and 4
d
electrons that are compatible with one atomic structure. The first assumption makes it possible to explain the absence of uncompensated spins of 4
d
electrons in the low-temperature antiferromagnetic (AFM) phase of FeRh. The second assumption is proposed to explain the strong changes in the spin structure of the FeRh alloy upon the AFM–FM transition, while its atomic structure is almost unchanged. Attempts have been made to predict the new properties of the FeRh alloy that follow from these assumptions. Our second assumption proved to be successful and enabled us to predict the existence of local magnetic moments of 3
d
electrons in the AFM phase, which are larger than the magnetic moments of Fe ions. Measurements of the magnetic susceptibility of the FeRh alloy in the AFM phase confirmed this prediction.
The review considers the principal, as well as less common but promising, methods to determine the fatty acids (FAs) in biological samples. The advantages, disadvantages, and prospects of these ...methods are described and compared. Special attention is paid to specific features of the preparation of biological samples, such as the extraction of lipids and derivatization process of FAs. Methodological aspects of the determination of FAs via gas chromatography (GC) and high-performance liquid chromatography (HPLC) and features of the applications of various types of stationary phases used for the chromatographic separation of FAs are considered. The potential for the use of capillary electrophoresis (CE) and nuclear magnetic resonance spectroscopy (NMR) to analyze FAs are analyzed. The special requirements and limitations of these methods concerning work with biomaterials are also considered
One of the main problems of magnonics is finding the ways of efficiently spin waves excitation in a magnet. This paper considers the method of nonlinear amplification by phase locking of amplitude of ...dynamic magnetization in yttrium-iron garnet film performed by micromagnetic modeling with MuMAX3 software taking into account the real materials parameters. It is shown that the excited magnetization precession can be considered as a autoresonance phenomena. The intensity of the autoresonance in ferrimagnetic yttrium-iron garnet films has threshold dependence on the chirp rate of the exciting magnetic field.
The specific features of dependences of the magnetic anisotropy constants on the thickness of yttrium iron garnet films prepared by pulsed laser deposition were studied. Films with thicknesses of ...96–333 nm were produced by pulsed laser evaporation of the target material and deposition onto gadolinium-gallium-garnet substrates with the (111) orientation. The results of an investigation into static magnetic properties showed that the saturation magnetization decreases as the films get thinner. The high-frequency properties were studied by ferromagnetic resonance (FMR). The uniaxial and cubic anisotropy fields and the relaxation parameter were determined by analyzing the angular dependences of the resonance field and the FMR line width. It was found that as the thickness decreases, the strength of the uniaxial anisotropy field increases monotonically, while the cubic anisotropy field decreases and reverses its sign.
It is shown that the magnetotransmission of unpolarized infrared radiation in the magnetostrictive crystal of CoFe
2
O
4
ferrite spinel in the Faraday geometry can be as high as 30% at a magnetic ...field of 7.5 kOe. This effect is related to the field-induced shift of the fundamental absorption edge, as well as to changes in the intensity and positions of the impurity absorption bands. Correlation between the magnetic field dependence of magnetotransmission and magnetostriction is revealed. The contribution of the Faraday effect to the magnetotransmission is estimated. The analysis of magneto-optical and magnetoelastic characteristics taking into account the contribution of the deformation potential for the valence band is performed.
The spectral, temperature, and field dependences of the Faraday effect in the IR spectral range have been studied in single crystals of the CoFe
2
O
4
ferrimagnetic spinel. It is established that the ...magneto-optical quality factor of CoFe
2
O
4
spinel varies from –60 to +20°/dB in a wavelength range of 1.5–10 μm and weakly depends on the temperature in a 200–300 K interval. Physical mechanisms are proposed that may be responsible for the Faraday effect.
PDF
