Elementary specific spin and orbital moments of ultrathin CoFeB amorphous films on GaAs(100)

TL;DR

This study reveals that ultrathin amorphous CoFeB films on GaAs(100) exhibit significantly enhanced orbital to spin magnetic moments, correlating with large magnetic anisotropy, which is promising for spintronics.

Contribution

It provides experimental evidence linking enhanced spin-orbital moments to magnetic anisotropy in ultrathin amorphous CoFeB films on GaAs(100).

Findings

Orbital to spin moment ratio increased by over 300%.

Large orbital moment observed in Co atoms.

Enhanced spin-orbital coupling correlates with magnetic anisotropy.

Abstract

Nanoscale CoFeB amorphous films have been synthesized on GaAs(100) and studied with X-ray magnetic circular dichroism (XMCD) and transmission electron microscopy (TEM). We have found that the ratios of the orbital to spin magnetic moments of both the Co and Fe in the ultrathin amorphous film have been enhanced by more than 300% compared with those of the bulk crystalline Co and Fe, and in specifically, a large orbital moment of 0.56*10^-6 B from the Co atoms has been observed and at the same time the spin moment of the Co atoms remains comparable to that of the bulk hcp Co. The results indicate that the large uniaxial magnetic anisotropy (UMA) observed in the ultrathin CoFeB film on GaAs(100) is related to the enhanced spin-orbital coupling of the Co atoms in the CoFeB. This work offers experimental evidences of the correlation between the UMA and the elementary specific spin and orbital moments in the CoFeB amorphous film on the GaAs(100) substrate, which is significant for spintronics applications.