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

P. R. Ohodnicki, Carnegie Mellon University
K. Y. Goh, Carnegie Mellon University
Y. Hanlumyuang, Carnegie Mellon University
K. Ramos, Carnegie Mellon University
M. E. McHenry, Carnegie Mellon University
Z. Cai, Northeastern University
K. Ziemer, Northeastern University
H. Morkoc, Virginia Commonwealth University
N. Biyikli, Virginia Commonwealth University
Z. Chen, Northeastern University
C. Vittoria, Northeastern University
V. G. Harris, Northeastern University

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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.