Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/8160
Title: Effect of microstructural evolution on magnetic properties of Ni thin films
Authors: Kumar, P
Krishna, MG
Bhattacharya, AK
Keywords: Magnetic thin films;Thermal evaporation;Substrate temperature;Atomic force microscopy;Phase contrast imaging
Issue Date: 2009
Publisher: Indian Academy of Sciences
Citation: Bulletin of Materials Science, 32(3), 263 - 270, 2009
Abstract: The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.
Description: Copyright © Indian Academy of Sciences.
URI: http://link.springer.com/article/10.1007%2Fs12034-009-0040-x
http://bura.brunel.ac.uk/handle/2438/8160
DOI: http://dx.doi.org/10.1007/s12034-009-0040-x
ISSN: 0250-4707
Appears in Collections:Materials Engineering
Wolfson Centre for Materials Processing

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