Structural and Morphological Characterization of Nanostructured Cobalt Ferrite Thin Films by Pulsed Laser Deposition
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0962-P09-08
Structural and Morphological Characterization of Nanostructured Cobalt Ferrite Thin Films by Pulsed Laser Deposition K. Mohan Kant1,2 and M.S. Ramachandra Rao1,2 1 Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India 2 Materials Science Research Centre, Indian Institute of Technology Madras, Chennai, 600036, India
ABSTRACT Cobalt ferrite (CoFe2O4) thin films were deposited on quartz and single crystalline MgO (001) substrates using pulsed laser deposition (PLD) technique. The orientation of the asdeposited films were investigated as a function of substrate temperature (TS) in the range 200oC 750oC. Films grown on MgO at higher substrate temperature were found to be (001) oriented while the films grown at lower substrate temperature were polycrystalline in nature. Magnetic measurements reveal that films deposited at lower substrate temperature yielded lower magnetic moment compared to that of films grown with higher substrate temperature, indicating the correlation between magnetic order and crystallinity. This is attributed to the presence of ordered magnetic domains in the oriented films even though the microstructure remains the same.
INTRODUCTION
Research on cobalt ferrite thin films has been very active because of the excellent magnetic and magneto-optic properties offered by them towards various device applications. CoFe2O4 (CFO) is one of the most suitable candidates for high-density recording media because of its high coercivity, high magneto-crystalline anisotropy and moderate saturation magnetization values [1,2]. CoFe2O4 has inverse spinel structure, AB2O4, in which the octahedral B sites are occupied by eight Co2+ and eight Fe3+ cations, while the tetrahedral A sites are occupied by eight Fe3+ cations. In the case of thin films there is a strong evidence for the dominant role of strain on the magnetic anisotropy [3]. By selecting substrates of different lattice parameters, it is possible to change the preferred orientation of the films, the amount of stress imposed and hence the magnetic properties of the CFO films [4]. In this work, epitaxial cobalt ferrite CoFe2O4 thin films were fabricated by pulsed laser deposition (PLD) on MgO (100) substrates. These substrates were chosen because they have a good lattice match with spinel ferrites. It has been reported in literature that epitaxial MnZn-ferrite films on MgO (100) could be achieved at relatively low growth temperatures [5] as compared to other thin film techniques [6–10]. Since most practical applications of Co-ferrite such as magnetic recording and magnetooptic recording require low-temperature processing in order to realize defect free interfaces that could influence the magnetic properties, we have chosen substrate temperature (TS) as the variable growth parameter and examined the dependence of TS on morphological and magnetic properties.
EXPERIMENT Polycrystalline Cobalt ferrite sample was prepared using conventional solid-state method. High pure chemicals were weighed stoichiometrically ,mixed tho
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