Defect-induced magnetic order in pure ZnO films

Abstract

We have investigated the magnetic properties of pure ZnO thin films grown under N 2 pressure on a-, c-, and r-plane Al 2 O 3 substrates by pulsed-laser deposition. The substrate temperature and the N 2 pressure were varied from room temperature to 570°C and from 0.007 to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c-and a-plane Al 2 O 3 substrates did not show significant ferromagnetism. However, ZnO films grown on r-plane Al 2 O 3 showed reproducible ferromagnetism at 300 K when grown at 300-400°C and 0.1-1.0 mbar N 2 pressure. Positron annihilation spectroscopy measurements as well as density-functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

Defect-induced magnetism in undoped wide band gap oxides: Zinc vacancies in ZnO as an example

“…Indeed, experimental observations of ferromagnetism in ZnO thin films 23 and pure ZnO powders 24,25 have been attributed to the intrinsic defects. It was also proposed that defects like Zn and O vacancies, 23,[26][27][28][29][30][31] [35][36][37][38][39][40][41] suggesting that the underlying physics is universal. However, open questions still remain related to this approach of defect engineering towards magnetism in oxides: e.g., what kinds of defects can contribute magnetic moments?…”

Structural and magnetic properties of irradiated SiC

“…It challenges the mJ paradigm for magnetism, where m refers the local moment and J stands for the interaction between the local moments. Experimentally, defect-induced ferromagnetism was observed in many materials, including graphite [2][3][4][5] and various oxides [6][7][8][9][10][11][12]. SiC single crystals are emerging as another candidate for this investigation and have been shown to be ferromagnetic after particle irradiation [13,14] or after aluminum doping [15].…”

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

“…A fundamental question is whether materials containing only s or p electrons can be ferromagnetic. For nearly two decades, there have been various theoretical and experimental studies devoted to clarifying this question [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It turns out that materials with completely filled 3d or 4f shells or with only s or p electrons can be ferromagnetic when they contain defects.…”