Uniaxial Magnetic Anisotropy in Amorphous CoFeB Films on Different Orientational GaAs Substrates

In-plane uniaxial magnetic anisotropy (UMA) has been carefully studied for the same amorphous Co
₅₆
Fe
₂₄
B
₂₀
(CoFeB) film deposited on different orientational GaAs substrates. It was noted that a strong uniaxial anisotropy field (
${H_{k}}$
) of
$\sim$
270 Oe could be achieved with CoFeB film grown on GaAs(001) substrate, which is much larger than the largest value (150 Oe) reported before. In contrast, Hk was <20 Oe when the same CoFeB film was deposited on (110) or (111) GaAs substrate. The angular dependence of Hk also behaved quite differently in these CoFeB films. Based on the surface morphology of the CoFeB/GaAs films, the possible mechanisms responsible for the different behavior of UMA were briefly discussed in terms of bond-orientational anisotropy model and random anisotropy model.