Amorphous nonstoichiometric oxides with tunable room-temperature ferromagnetism and electrical transport

Qinghao Li; Ruimin Qiao; Apurva Mehta; Weiming Lü; Tie Zhou; Elke Arenholz; Cheng Wang; Yanxue Chen; Li Li; Yufeng Tian; Lihui Bai; Zahid Hussain; Rongkun Zheng; Wanli Yang; Shishen Yan

doi:10.1016/j.scib.2020.06.035

Amorphous nonstoichiometric oxides with tunable room-temperature ferromagnetism and electrical transport

Sci Bull (Beijing). 2020 Oct 30;65(20):1718-1725. doi: 10.1016/j.scib.2020.06.035. Epub 2020 Jun 26.

Authors

Qinghao Li¹, Ruimin Qiao², Apurva Mehta³, Weiming Lü⁴, Tie Zhou⁵, Elke Arenholz⁶, Cheng Wang², Yanxue Chen⁵, Li Li⁷, Yufeng Tian⁵, Lihui Bai⁵, Zahid Hussain², Rongkun Zheng⁷, Wanli Yang⁸, Shishen Yan⁹

Affiliations

¹ Spintronics Institute, University of Jinan, Jinan 250022, China; Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
² Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
³ SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
⁴ Spintronics Institute, University of Jinan, Jinan 250022, China.
⁵ School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.
⁶ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY 14853, USA.
⁷ School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia.
⁸ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Electronic address: wlyang@lbl.gov.
⁹ Spintronics Institute, University of Jinan, Jinan 250022, China. Electronic address: shishenyan@sdu.edu.cn.

PMID: 36659244
DOI: 10.1016/j.scib.2020.06.035

Abstract

Material functionalities strongly depend on the stoichiometry, crystal structure, and homogeneity. Here we demonstrate an approach of amorphous nonstoichiometric inhomogeneous oxides to realize tunable ferromagnetism and electrical transport at room temperature. In order to verify the origin of the ferromagnetism, we employed a series of structural, chemical, and electronic state characterizations. Combined with electron microscopy and transport measurements, synchrotron-based grazing incident wide angle X-ray scattering, soft X-ray absorption and circular dichroism clearly reveal that the room-temperature ferromagnetism originates from the In_0.23Co_0.77O_1-_v amorphous phase with a large tunable range of oxygen vacancies. The room-temperature ferromagnetism is tunable from a high saturation magnetization of 500 emu cm^-3 to below 25 emu cm^-3, with the evolving electrical resistivity from 5 × 10³ μΩ cm to above 2.5 × 10⁵ μΩ cm. Inhomogeneous nano-crystallization emerges with decreasing oxygen vacancies, driving the system towards non-ferromagnetism and insulating regime. Our work unfolds the novel functionalities of amorphous nonstoichiometric inhomogeneous oxides, which opens up new opportunities for developing spintronic materials with superior magnetic and transport properties.

Keywords: Amorphous oxide; Grazing incident wide angle X-ray scattering; Room-temperature ferromagnetism; Soft X-ray spectroscopy.