Enhancing the magnetic moment of ferrimagnetic NiCo2O4 via ion irradiation driven oxygen vacancies

• Published in: APL materials Vol. 6; no. 6; pp. 066109 - 066109-9
• Main Authors: Pandey, Parul, Bitla, Yugandhar, Zschornak, Matthias, Wang, Mao, Xu, Chi, Grenzer, Jörg, Meyer, Dirk-Carl, Chin, Yi-Ying, Lin, Hong-Ji, Chen, Chien-Te, Gemming, Sibylle, Helm, Manfred, Chu, Ying-Hao, Zhou, Shengqiang
• Format: Journal Article
• Language: English
• Published: AIP Publishing LLC 01.06.2018
• ISSN: 2166-532X; 2166-532X
• DOI: 10.1063/1.5036941

Ion irradiation has emerged as a powerful tool for the efficient control of uniaxial lattice expansion to fine tune and modulate the otherwise inaccessible complex correlated phases in oxide thin-films. We report the fine tuning of the magnetic moment, ferromagnetic-paramagnetic and metal-insulator transition temperatures in the NiCo2O4 inverse-spinel oxide by creating oxygen deficiencies, employing high energy He-ion irradiation. Tailoring of oxygen vacancies and consequently a uniaxial lattice expansion in the out-of-plane direction drives the system toward the increase of the magnetic moment by two-times in magnitude. The magnetic moment increases with the He-ion irradiation fluence up to 2.5 × 1016/cm2. Our results are corroborated well by spin-polarized electronic structure calculations with density functional theory and X-ray absorption spectroscopic data, which show peak-height change and energy shift of Co-L2,3 and Ni-L2,3 edges driven by the oxygen vacancies. These results demonstrate a new pathway of tailoring oxygen vacancies via He-ion irradiation, useful for designing new functionalities in other complex oxide thin-films.