Magnetic anisotropy of [(Co$_{41}$Fe$_{39}$B$_{20}$)$_{x}$(SiO$_{2}$)$_{100-x}$/Bi$_{2}$Te$_{3}$]$_{47}$ multilayer heterostructures

Magnetic anisotropy values are obtained for [(Co$_{41}$Fe$_{39}$B$_{20}$)$_{x}$(SiO$_{2}$)$_{100-x}$/Bi$_{2}$Te$_{3}$]$_{47}$ heterostructures consisting of SiO$_2$ alternating layers, CoFeB nanoparticles distributed in them, and Bi$_2$Te$_3$ layers with ferromagnetic resonance and magnetometry. The heterostructures have anisotropy of $\sim$10$^6$ erg/cm$^3$, which orients the magnetic moment in films plane. The films are not solid, but they disintegrate into CoFeB nanoparticles with an average diameter of 5 nm during deposition, which corresponds to the blocking magnetization temperature of $\sim$30 K during their saturation magnetization of $M_S$ = 720 emu/cm$^3$. The relationship between anisotropy constant and thickness of the layers of the heterostructures is nonmonotonic due to competition between surface and bulk anisotropies of the ferromagnetic granules, which the films are made of.