Abstract
First principles band structure calculations suggest that the preferential occupation of Ni2+ ions on the tetrahedral sites in NiFe₂O₄ would lead to an enhancement of the exchange integral and subsequently the Néel temperature and magnetization. To this end, we have deposited NiFe₂O₄films on MgO substrates by pulsed laser deposition. The substrate temperature was varied from 700 to 900°C at 5 mTorr of O₂ pressure. The films were annealed at 1000°C for different times prior to their characterization. X-ray diffraction spectra showed either (100) or (111) orientation with the spinel structure dependent on the substrate orientation. Magnetic studies showed a magnetization value of 2.7 kG at 300 K. The magnetic moment was increased to the bulk value as a result of postdeposition annealing at 1000°C. The as produced films show that the ferromagnetic resonance linewidth at 9.61 GHz was 1.5 kOe, and it was reduced to 0.34 kOe after postannealing at 1000°C. This suggests that the annealing led to the redistribution of Ni2+ ions to their equilibrium octahedral sites. Further, it is shown that the magnetically preferred direction of Ha can be aligned perpendicular to the film plane when films are grown with a fixed oxygen pressure of 5 mTorr for films deposited at 700 and 900°C.
Keywords
microwave properties, cation inversion, NiFe₂O₄, growth temperature, Ni2+ ions, Néel temperature, MgO substrates, X-ray diffraction, annealing, Ha
Subject Categories
Thin films, Ferromagnetism, Magnetic properties, Pulsed laser deposition, Laser ablation, Magnetization, Pulsed laser deposition, Ferromagnetic resonance
Disciplines
Electromagnetics and photonics
Publisher
American Institute of Physics
Publication Date
5-1-2007
Rights Information
Copyright 2007 American Institute of Physics.
Rights Holder
American Institute of Physics
Permanent URL
Recommended Citation
Chinnasamy, C. N.; Yoon, S. D.; Yang, Aria; Baraskar, Ashish; Vittoria, C.; and Harris, V. G., "Effect of growth temperature on the magnetic, microwave, and cation inversion properties on NiFe₂O₄ thin films deposited by pulsed laser ablation deposition" (2007). Electrical and Computer Engineering Faculty Publications. Paper 35. http://hdl.handle.net/2047/d20002205
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effect_of_growth_temp_fig1.zip (119 kB)Figure 1
effect_of_growth_temp_fig2.zip (58 kB)
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effect_of_growth_temp_fig3.zip (9 kB)
Figure 3
Notes
Originally published in Journal of Applied Physics 101, 09M517 (2007). DOI:10.1063/1.2714204 (http://dx.doi.org/10.1063/1.2714204).