Spin and Orbital Moments of Magnetic Topological Insulator MnBi2Te4 Epitaxial Thin Films

Intrinsic magnetic topological insulators (MTIs) have proven to be an important material system for the study of quantum effects and the development of novel electronic devices. Unlike the magnetically doped topological insulators (TIs)., intrinsic MTIs well preserve the crystalline ordering and homogeneity of the pristine TIs, leading to enhanced quantum coherency in many cases. Here, we report a detailed study of the atomic scale spin
$(m_{\mathrm{s}})$
and orbital
$(m1)$
moments of an epitaxial
$\text{MnBi}_{2}\text{Te}\triangleleft$
thin film. The synchrotron-based x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements were performed to investigate the electronic and magnetic properties of the thin film at 3 K and up to 14 T. The 16.3 nm
$\text{MnBi}_{2}\text{Te}4/\mathrm{A}1_{2}\mathrm{O}_{2}$
shows reduced moments of
$m_{\mathrm{s}}= (1.64\pm 0.2)\mu_{\mathrm{B}}/\text{Mn}$
and
$m1=(0.16\pm 0.02)\mu_{\mathrm{B}}/\text{Mn}$
at 14 T compared to their bulk counterparts. The reduced magnetic moments may be attributed to the weakened intralayer or interlayer exchange interaction and the intrinsic structural defects of the materials. Future work to understand the correlations between the structural defects, intralayer or interlayer exchange interactions, and magnetic properties will have strong implications for both fundamental physics and practical applications of the
$\text{MnBi}_{2}\text{Te}_{4}$
materials.