X-ray absorption spectroscopy investigation of relationship between Mg vacancy and magnetic properties of MgO powder

Abstract

This paper reports on the ferromagnetism of MgO powder and degraded powder at room temperature. The starting material, Mg(OH)2, was analyzed by X-ray fluorescence (XRF) spectrometry and then calcined at 450 °C for 5 h to obtain fresh MgO powder. The calcined powder was separated into two batches (i) kept in vacuum sealed (MgO-F) and (ii) kept at ambient environment (30–32 °C at 45–55% relative humidity) for 2 days (MgO-D). The samples were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and X-ray absorption spectroscopy (XAS) including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). XRD and EXAFS confirmed that MgO phase in MgO-F. Both Mg(OH)2 and MgO compositions were found in MgO-D. The origin of ferromagnetism at room temperature of MgO-F and MgO-D is attributed to the Mg vacancies in the MgO structure that revealed and verified by XANES and EXAFS results.