Observing the orbital angular momentum of Fe and Co in chiral magnet Fe0.75Co0.25Si using soft x-ray magnetic circular dichroism

Abstract

The intermetallic compound Fe[Formula: see text]Co[Formula: see text]Si has a helical magnetic order for [Formula: see text], whereas its orbital angular momentum contributing to the occurrence of a Dzyaloshinskii–Moriya interaction has not yet been verified. We applied soft x-ray magnetic circular dichroism spectroscopy on the Fe [Formula: see text] and Co [Formula: see text] edges below [Formula: see text] for Fe[Formula: see text]Co[Formula: see text]Si such that their orbital magnetic moments [Formula: see text] were evaluated independently. The dichroic signals provide direct experimental evidence that [Formula: see text] for both Fe and Co is coupled in a parallel manner with each spin counterpart [Formula: see text]. The ratio of [Formula: see text] to [Formula: see text] is independently estimated as [Formula: see text]/[Formula: see text]% for Fe and 9% for Co. By comparing the average of the two [Formula: see text] values with the saturated magnetization using a commercial superconducting quantum interference device (SQUID) magnetometer, the hole number in the [Formula: see text] bands for both Fe and Co is roughly estimated as approximately 1.5. This suggests that Fe and Co should be arranged closely for stabilizing the ferromagnetic moments.