Easy-cone state in spin-torque diode under combined action of magnetostatics and perpendicular anisotropy

Spin-torque diodes (STDs) with interfacial perpendicular magnetic anisotropy (IPMA) in the free layer have outstanding microwave signal rectification performances. Large sensitivity values in such systems are usually associated with an easy cone (EC) magnetic state, when the magnetization in the free layer is tilted from the normal to the plane of the film. Here we theoretically investigate the phase diagram of the existence of an EC state in an infinite free layer of the magnetic tunnel junction (MTJ) considering both IPMA (first and second order) and magnetostatic interaction. We show that the increase of the magnetostatic field leads to extension of the EC existence region. Then we consider the effect of finite dimensions in case of two differently spatially oriented elliptic nanopillar MTJ on the obtained phase diagrams. And finally, we consider dynamic properties and rectification of two elliptic STD under microwave current injection. These results clarify magnetostatic interaction influence on IPMA based STD rectification and demonstrate possible approach to extend the parameters area of the EC STD highly effective rectification.

The Bloch point 3D topological charge induced by the magnetostatic interaction

A hedgehog or Bloch point is a point-like 3D magnetization configuration in a ferromagnet. Regardless of widely spread treatment of a Bloch point as a topological defect, its 3D topological charge has never been calculated. Here, applying the concepts of the emergent magnetic field and Dirac string, we calculate the 3D topological charge (Hopf index) of a Bloch point and show that due to the magnetostatic energy contribution it has a finite, non-integer value. Thus, Bloch points form a new class of hopfions—3D topological magnetization configurations. The calculated Bloch point non-zero gyrovector leads to important dynamical consequences such as the appearance of topological Hall effect.

Analysis of Remagnetization Processes of High-Anisotropic Alloy after Heat Treatment

The simulation of the Sm(Co, Fe, Cu, Zr)7.5 type alloy domain structure formation after various thermal treatments was carried out by FMRM program based on a phenomenological approach to the analysis of the uniaxial highly anisotropic ferromagnets demagnetization processes. It is shown that the domain structure of the alloy in the thermally demagnetized state expands as the coercive force of the alloy decreases. It is noted that the domains size increasing process is associated not only with a decrease in the coercive force but also with a change in the influence of the magnetostatic interaction.

Blocking Temperature of a System of Core/Shell Nanoparticles

A theoretical study was made of the dependence of the blocking temperature of the core/shell system of nanoparticles on the intensity of their magnetostatic interaction. It is shown that with an increase in the concentration of nanoparticles (intensity of the magnetostatic interaction), the blocking temperature increases. Moreover, the of large nanoparticles changes more significantly.

Магнитные состояния двухфазных синтезированных частиц Fe-=SUB=-m-=/SUB=-O-=SUB=-n-=/SUB=--Fe-=SUB=-3-x-=/SUB=-Ti-=SUB=-x-=/SUB=-O-=SUB=-4-=/SUB=-: экспериментальный и теоретический анализ

In this work, the materials of FemOn – Fe3-xTixO4 composition have been obtained using the sol-gel method and hydrothermal treatment. The synthesis conditions favor the formation of composites containing titanomagnetite in a rather low concentration. Based on the hysteresis curves and temperature dependences of the remanent magnetization, theoretical analysis of the composites magnetic properties has been carried out using a model of clustered two-phase particles bound with magnetostatic interaction.

Моделирование вынужденных колебаний намагниченности в системе трех ферромагнитных нанодисков

A micromagnetic simulation of ferromagnetic resonance (FMR) was carried out in a system consisting of a cylindrical stack consisting of three ferromagnetic nanodisks, in which a helicoidal distribution of magnetic moments is realized due to magnetostatic interaction in the equilibrium state. The features of tuning the FMR spectrum and the spatial structure of the resonance modes of oscillations of such a system in an external magnetic field are investigated.