Effect of hydrogen on magnetic properties in MgO studied by first-principles calculations and experiments

Ittipon Fongkaew; Benjaporn Yotburut; Wutthigrai Sailuam; Warakorn Jindata; Theerawee Thiwatwaranikul; Atchara Khamkongkaeo; Nattapong Chuewangkam; Nantawat Tanapongpisit; Wittawat Saenrang; Rapee Utke; Prasit Thongbai; Supree Pinitsoontorn; Sukit Limpijumnong; Worawat Meevasana

doi:10.1038/s41598-022-13949-w

Effect of hydrogen on magnetic properties in MgO studied by first-principles calculations and experiments

Sci Rep. 2022 Jun 16;12(1):10063. doi: 10.1038/s41598-022-13949-w.

Authors

Affiliations

¹ School of Physics, Suranaree University of Technology, 111 University Ave., Nakhon Ratchasima, 30000, Thailand.
² Department of Applied Physics, Faculty of Engineering, Rajamangala University of Technology ISAN (Khon Kaen Campus), Khon Kaen, 40000, Thailand.
³ Department of Metallurgical Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand.
⁴ Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen, 40002, Thailand.
⁵ School of Chemistry, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.
⁶ School of Physics, Suranaree University of Technology, 111 University Ave., Nakhon Ratchasima, 30000, Thailand. worawat@g.sut.ac.th.
⁷ Thailand Center of Excellence in Physics (ThEP), MHESI, Bangkok, 10400, Thailand. worawat@g.sut.ac.th.

Abstract

We investigated the effects of both intrinsic defects and hydrogen atom impurities on the magnetic properties of MgO samples. MgO in its pure defect-free state is known to be a nonmagnetic semiconductor. We employed density-functional theory and the Heyd-Scuseria-Ernzerhof (HSE) density functional. The calculated formation energy and total magnetic moment indicated that uncharged [Formula: see text] and singly charged [Formula: see text] magnesium vacancies are more stable than oxygen vacancies (V_O) under O-rich growth conditions and introduce a magnetic moment to MgO. The calculated density of states (DOS) results demonstrated that magnetic moments of V_Mg result from spin polarization of an unpaired electron of the partially occupied valence band, which is dominated by O 2p orbitals. Based on our calculations, V_Mg is the origin of magnetism and ferromagnetism in MgO. In contrast, the magnetic moment of the magnetic V_Mg-MgO crystal is suppressed by hydrogen (H) atoms, and unpaired electrons are donated to the unpaired electronic states of V_Mg when the defect complex H_i-V_Mg is formed. This suggests that H causes a reduction in magnetization of the ferromagnetic MgO. We then performed experimental studies to verify the DFT predictions by subjecting the MgO sample to a thermal treatment that creates Mg vacancies in the structure and intentionally doping the MgO sample with hydrogen atoms. We found good agreement between the DFT results and the experimental data. Our findings suggest that the ferromagnetism and diamagnetism of MgO can be controlled by heat treatment and hydrogen doping, which may find applications in magnetic sensing and switching under different environmental conditions.