Field dependence of orbital magnetic moments in the Heusler compounds Co₂FeAl and Co₂Cr_0.6Fe_0.4Al

Orbital and spin magnetic moments of the Heusler compounds Co2FeAl and Co2Cr0.6Fe0.4Al were measured by magnetic circular dichroism in X-ray absorption (XMCD). The orbital magnetic moments per spin are quite large (0.1-0.2) compared to bulk values of Fe and Co metals, indicating a considerable spin-orbit coupling in these Heusler compounds. A strong localization of the 3d electron states might be responsible for this observation. The Co and Fe orbital to spin moment ratio shows a distinct decrease of Deltar(Fe) = 0.04 +/- 0.02 and Deltar(Co) = 0.06 +/- 0.02 with increasing external field for the ternary compound Co2FeAl, while the ratio is within error limits independent of the field for Co2Cr0.6Fe0.4Al. This is discussed in terms of a relation to magnetocrystalline anisotropies