npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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Article

Research Paper

New Physics: Sae Mulli 2016; 66: 523-528

Published online May 31, 2016 https://doi.org/10.3938/NPSM.66.523

Copyright © New Physics: Sae Mulli.

Thickness Dependence of the Perpendicular Magnetic Anisotropy and Magnetic-domain Structures in Nickel-ferrite Films

Byeong-geon KIM1, Joonghoe DHO*1, Sungjo JEONG2, Haeng Beom SHIN2, Hyeon Tae JO2, Bo Guk CHA2

1 Department of Physics, Kyungpook National University, Daegu 41566, Korea
2 Daegu Science High School, Daegu 42110, Korea

Correspondence to:jhdho@knu.ac.kr

Received: December 14, 2015; Revised: January 25, 2016; Accepted: January 27, 2016

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

Inverse spinel NiFe$_{2}$O$_{4}$ (NFO) films were prepared on (110) MgAl$_{2}$O$_{4}$ substrates by using pulsed laser deposition. The NFO films were deposited at a substrate temperature of 600 $^\circ$C and an oxygen partial pressure of 1 mTorr, and their thicknesses were in the range of 20 nm - 240 nm. As the film's thickness increased, the positon of the (440) NFO peak moved to a higher angle, implying a relaxation of the lattice strain. For 240 nm, the lattice constant of the NFO film was about 8.39 Å, which corresponded to a lattice mismatch of about 0.6% with the lattice constant of the NFO bulk. The magnetic hysteresis measurement suggested an increasing tendency of the perpendicular magnetic anisotropy with increasing film thickness. For 160 nm, the ratio of the remanent magnetization to the saturation magnetization (M$_{rem.}$/M$_{sat.}$) was maximally $\sim$0.22. The magnetic domain structure was observed by using magnetic force microscopy. The image contrast was improved with increasing film thickness, and it was the best for a film with a thickness of 160 nm.

Keywords: Ferrite, Film, Magnetic anisotropy, Magnetic domain imaging

Figures

Fig. 1. (a)-(e) MFM images of NiFe2O4 films (image size: 2 μm × 2 μm), and (f) the RMS contrast of MFM images as a function of film thickness.

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