Evolution of structural and magnetic properties and the electronic structure of spinel Fe/sub x/Co/sub 3-x/O/sub 4/ thin films

• Published in: IEEE transactions on magnetics Vol. 41; no. 10; pp. 3478 - 3480
• Main Authors: Kim, Kwang Joo, Kim, Hee Kyung, Park, Young Ran, Ahn, Geun Young, Kim, Chul Sung, Park, Jae Yun
• Format: Journal Article
• Language: English
• Published: IEEE 01.10.2005
• Subjects: Crystal structure; Iron; Lattices; Magnetic films; magnetic hysteresis; Magnetic properties; MÖssbauer spectroscopy; optical absorption; Optical films; Optical saturation; Phase measurement; Saturation magnetization; Spectroscopy; spinel; X-ray diffraction
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2005.854914

Evolution of structural, optical, and magnetic properties has been investigated for sol-gel-grown spinel Fe/sub x/Co/sub 3-x/O/sub 4/ thin films as the Fe composition (x) increases from 0 to 2. The crystal structure of Fe/sub x/Co/sub 3-x/O/sub 4/ is found to remain cubic with the lattice constant increasing with increasing x. Coexistence of two phases is observed by X-ray diffraction for 0.76/spl les/x/spl les/0.93, interpreted as due to normal spinel, dominant for x/spl les/0.55, and inverse spinel, dominant for x/spl ges/1.22. Analysis on the measured optical absorption spectra by spectroscopic ellipsometry for the samples indicates the dominance of the normal spinel phase for low x in which Fe/sup 3+/ ions mostly substitute octahedral Co/sup 3+/ sites. X-ray photoelectron spectroscopy measurements revealed that both Fe/sup 2+/ and Fe/sup 3+/ ions exist with similar strength in the x=0.93 sample. Vibrating sample magnetometry measurements revealed that the Fe/sub x/Co/sub 3-x/O/sub 4/ films start exhibiting magnetic hysteresis behaviors for x/spl ges/0.76 with the saturation magnetization increasing with increasing x. Conversion electron Mo/spl uml/ssbauer spectra measured on the x=0.93 sample showed that Fe/sup 2+/ ions prefer the octahedral sites, indicating the formation of the inverse spinel phase. The remarkable change of the lattice constant for x/spl ges/0.76 is derivable from the site preference of the Fe/sup 2+/ and Fe/sup 3+/ ions.