Probing defect driven tunable spontaneous magnetization in paramagnetic Zn0.95Co0.05O epitaxial films by X-ray absorption investigations

Abstract In order to address existing unresolved issues related to intrinsic and extrinsic origins of ferromagnetism in Zn 1−x Co x O based diluted magnetic semiconductors for varying x, the present work aims to investigate the tunable ferromagnetism triggered in paramagnetic Zn 0.95 Co 0.05 O films using 500 KeV inert xenon ion irradiation of different fluences. The origin of ferromagnetism in post irradiated Zn 0.95 Co 0.05 O films is understood from different densities of bound magnetic polarons (BMPs) formation through correlated spins of tetrahedrally substituted Co 2+ ions and anionic vacancies. The alteration in crystallographic positions of Zn, Co cations, and O anions in the tetrahedral environment as analyzed from Zn and Co K-edgeX-ray absorption and O 1s photoemission is a crucial factor for the stabilization of different density of BMPs. Magnetic field and temperature dependence of X-ray magnetic circular dichroism at the Co L 2,3 edge provide experimental evidence of purely paramagnetic contribution from well localized Co 2+ ions of Co sublattice for paramagnetic Zn 0.95 Co 0.05 O film. The paramagnetic Co 2+ ions of Co sublattice persist in irradiated films, which reveal BMPs formation as the origin of ferromagnetism.