Perpendicular magnetic anisotropy properties of tetragonal Mn3Ga films under various deposition conditions

Abstract

The tetragonal Mn3Ga films exhibited high perpendicular magnetic anisotropy, low saturation magnetization, and high spin polarization, which satisfy the criteria of spin-transfer-torque based devices. For practical device applications, it is necessary to improve the interface nature and optimize the deposition conditions. We fabricated thin films of tetragonal Mn3Ga directly on MgO(100) without any buffer layer by using DC/RF magnetron sputtering method. We investigated the crystallinity, microstructure, and magnetic properties with varying the deposition conditions; such as deposition temperature (350-450 °C), RF power (25-40 W), and Ar gas pressure (2-7 mTorr). X-ray diffraction data revealed that the growth direction is perpendicular to the film plane, i.e., the c axis. Scanning electron microscope images showed that the top surface is flat with a maximum thickness of 290 nm. The optimal deposition conditions are 400 °C, 35 W, and 5 mTorr in our sputtering system. For the field perpendicular to the film plane, clear hysteresis loop was observed with the saturation magnetization MS = 100 emu/cc at room temperature. By extrapolating the hard magnetization data for the field parallel to the film plane, the anisotropic energy was estimated about K1 = 1 × 106 J/m3. © 2015 Published by Elsevier B.V.