Abnormal magnetic properties of MnBi thin film synthesized by MBE

MnBi has attracted much attention due to its unusual magnetic properties. It has the potential as an alternative to the permanent magnets containing rare-earth elements. In this paper, the MnBi thin film was grown by plasma-assisted molecular beam epitaxial technique. The as-grown film shows ferromagnetic property and an anomalous magnetization dependence on temperature. The X-ray photoelectron spectrum reveals that there are regular and interstitial sites Mn atoms with two bonding states. The observed decrease of magnetization at ∼230 K would be ascribed to the movements of Mn atoms to the interstitial sites leaving behind Mn vacancies. Also at ∼90 K, it exhibits a spin reorientation due to the magnetization change from c-axis to ab-plane which is related to the abnormal temperature dependence of the lattice parameters