Magnetic anisotropy and crystalline texture in BaO(Fe₂O₃)₆ thin films deposited on GaN/Al₂O₃

Paul R. Ohodnicki, Carnegie Mellon University - Pittsburgh PA
K. Y. Goh, Carnegie Mellon University - Pittsburgh PA
Yuranan Hanlumyuang, Carnegie Mellon University - Pittsburgh PA
K. Ramos, Carnegie Mellon University - Pittsburgh PA
Michael E. McHenry, Carnegie Mellon University - Pittsburgh PA
Zhuhua Cai, Northeastern University - Dept. of Chemical Engineering
Katherine Ziemer, Northeastern University - Dept. of Chemical Engineering
Hadis Morkoc, Virginia Commonwealth University - Richmond VA
Necmi Biyikli, Virginia Commonwealth University - Richmond VA
Zhaohui Chen, Northeastern University - Dept. of Electrical and Computer Engineering
C. Vittoria, Northeastern University - Dept. of Electrical and Computer Engineering
Vincent Girard Harris (1962-), Northeastern University - Dept. of Electrical and Computer Engineering

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Originally published in Journal of Applied Physics, vol.101, no.9, May 2007. doi: 10.1063/1.2712295

Abstract

BaO(Fe₂O₃)₆ (BaM) thin films were deposited by pulsed laser deposition on GaN/Al₂O₃ substrates. A pole figure obtained from the (006) reflection indicated that ~81% of the film volume had the c axis tilted less than 5° from the film normal. A low anisotropy field was inferred from vector coil vibrating sample magnetometer (VVSM) measurements. The reduction in Hₐ from literature values and a two-step switching of the easy axis magnetization is postulated to result from interdiffusion and misalignment effects. To alleviate interdiffusion and to improve the c-axis alignment, experiments were repeated with lower deposition temperatures, thinner films, and MgO buffer layers. The features of the hysteresis loop due to two-step switching and the in-plane coercivity were reduced while the anisotropy field (Hₐ) was larger. Films deposited with MgO buffer layers are observed to have single-step switching of the easy axis magnetization, larger anisotropy fields, and sharp ferromagnetic resonance (FMR) peaks. Films with MgO buffer layers were determined to have anisotropy fields Hₐ=1.57 T by FMR and Hₐ~1.5–1.6 T as determined from the difference in the saturation fields for the easy and hard axis loops.