Recovering the Magnetic Image of Mars from Satellite Observations

One of the possible approaches to reconstructing the map of the distribution of magnetization parameters in the crust of Mars from the data of the Mars MAVEN orbiter mission is considered. Possible ways of increasing the accuracy of reconstruction of the magnetic image of Mars are discussed.

Радиальные домены в микропроводах DyPr-FeCo-B

In DyPr-FeCo-B microwires with an easy magnetization axis directed along the microwire axis, domains with radial magnetization were found by the method of magneto-optical indicator films (MOIF). The width of the radial domains decreases with increasing field up to 30 mT, and increases with increasing diameter of the microwire in the range 60 - 105 μm. In wires of smaller diameter, the critical field for the appearance of radial domains is smaller. The influence of periodic scratches on the distribution of magnetization perpendicular to the microwire is found.

Nanoscale Mapping of Heterogeneous Strain and Defects in Individual Magnetic Nanocrystals

We map the three-dimensional strain heterogeneity within a single core-shell Ni nanoparticle using Bragg coherent diffractive imaging. We report the direct observation of both uniform displacements and strain within the crystalline core Ni region. We identify non-uniform displacements and dislocation morphologies across the core–shell interface, and within the outer shell at the nanoscale. By tracking individual dislocation lines in the outer shell region, and comparing the relative orientation between the Burgers vector and dislocation lines, we identify full and partial dislocations. The full dislocations are consistent with elasticity theory in the vicinity of a dislocation while the partial dislocations deviate from this theory. We utilize atomistic computations and Landau–Lifshitz–Gilbert simulation and density functional theory to confirm the equilibrium shape of the particle and the nature of the (111) displacement field obtained from Bragg coherent diffraction imaging (BCDI) experiments. This displacement field distribution within the core-region of the Ni nanoparticle provides a uniform distribution of magnetization in the core region. We observe that the absence of dislocations within the core-regions correlates with a uniform distribution of magnetization projections. Our findings suggest that the imaging of defects using BCDI could be of significant importance for giant magnetoresistance devices, like hard disk-drive read heads, where the presence of dislocations can affect magnetic domain wall pinning and coercivity.

Микромагнитное моделирование спин-волновых возбуждений в гофрированных пленках ЖИГ

Particularities of the spin-wave spectrum in YIG film with the thickness of 0.4 μm and magnetization of 1.1 kG that was corrugated due to the periodical substrate relief in the form of grooves having width of 10 μm, depth of 0.5 μm, sloped walls and period of 20 μm were studied with the help of micromagnetic modelling. Calculations were carried out for the external magnetic field applied along (θ=0) and across (θ=90°) the grooves in the film plane, and showed that the anisotropy from the film form caused the spectrum quantization and localization of spin-wave excitations in the different parts of the sample. Besides that, spacial distribution of magnetization amplitude at fixed frequencies in the spectrum for θ=90° can be characterized by several spacial scales that differ by orders. This is explained by the strong inhomogeneity of equilibrium state at grooves' walls for θ=90° that leads to the effective excitation of short-wave part of the spin-wave spectrum in the periodical structure by Schlömann mechanism.

Effect of spin-orbital interaction on continuous and jumpwise reversal magnetization in [Mn(II)(HL)(H2O)][Mn(III)(CN)6]·2H2O molecular ferrimagnet

Magnetic jumps were revealed during the magnetization reversal of [Mn(II)(HL)(H2O)][Mn(III)(CN)6]·2H2O molecular ferrimagnet. Amplitudes of the jumps were 0.01 – 0.1 % of the saturation magnetization. Fourier transform of the time series of jumps magnetization indicates that frequency spectrum is close to the white noise. Statistic distribution of the jumps versus time reveals the appearance of the most jumps at the beginning of the demagnetization. Effect of spin-orbit coupling on statistical distribution of magnetization jumps was considered by comparison of two compounds with different single ion anisotropies. The increase of spin-orbit interaction leads to the decrease of power of spectral density of magnetization jumps.