Magnetic anisotropy in multilayer nanogranular films (Co40Fe40B20) 50(SiO2)(50)/alpha-Si:H

Macroscopic and local magnetic anisotropy of [CoFeB-SiO₂/α-Si:H]₆₀ multilayer films was studied in comparison with that for the thick CoFeB-SiO₂ granular films. The volume fraction of magnetic component Co₄₀Fe₄₀B₂₀ is ranged from 0.34 to 0.70. In the multilayer films the magnetic layer and silicon spacer thicknesses are 2.5÷4.5 nm and 3.5 nm correspondingly. The magnetization curves and ferromagnetic resonance measurements were used to determining magnetic anisotropy energy constants. The main contribution to the local magnetic anisotropy energy constant is found to be from surface magnetic anisotropy of magnetic granules. It is found that the magnetic percolation point of multilayer films (X_C~40) is shifted in comparison with that in granular films (X_C~30). Surface magnetic anisotropy energy constants of multilayer films with different X evaluated from the surface modes of spin-wave resonance are in the range 0.5< K_s <0.9 erg/cm².