pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2018; 68: 522-528

Published online May 31, 2018 https://doi.org/10.3938/NPSM.68.522

## Electron Magnetic Resonance Study of Gd$^{3+}$ Ions in a $\beta$-Ga$_2$O$_3$ Single Crystal

Chong Shik OH, Tae Ho YEOM*

Department of Laser and Optical Information Engineering, Cheongju University, Cheongju 28503, Korea

Correspondence to:thyeom@cju.ac.kr

Received: March 30, 2018; Accepted: April 20, 2018

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

### Abstract

A single-domain $\beta$-Ga$_2$O$_3$ single crystal doped with the Gd$^{3+}$ ions was grown in an O$_2$ atmosphere by using a floating zone method. Electron magnetic resonance (EMR) spectra of the Gd$^{3+}$ impurity ions were recorded using an X-band EMR spectrometer at room temperature. From the analysis of the rotation patterns of the Gd$^{3+}$ ions in the crystallographic planes, the spectroscopic splitting tensor g and the zero-field splitting parameters $B_k^q$'s were determined using an effective spin Hamiltonian. The Gd$^{3+}$ impurity ions replace the Ga$^{3+}$ ions in the oxygen octahedron rather than in the oxygen tetrahedron. The actual local site symmetry of the Gd$^{3+}$ impurity ion substituting at the Ga$^{3+}$ site is unequivocally monoclinic. The energy levels of the ground state for Gd$^{3+}$ ions embedded in $\beta$-Ga$_2$O$_3$ crystals were calculated.

Keywords: $\beta$-Ga$_2$O$_3$ single crystal, EMR, Gd$^{3+}$ impurity ion, Energy level