Microstructure and random magnetic anisotropy in Fe–Ni based nanocrystalline thin films

• Published in: Journal of physics. D, Applied physics Applied physics, 2008-08, Vol.41 (15), p.155009-155009 (8)
• Main Authors: Thomas, Senoy, Al-Harthi, S H, Sakthikumar, D, Al-Omari, I A, Ramanujan, R V, Yoshida, Yasuhiko, Anantharaman, M R
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Physics
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/41/15/155009

Nanocrystalline Fe-Ni thin films were prepared by partial crystallization of vapour deposited amorphous precursors. The microstructure was controlled by annealing the films at different temperatures. X-ray diffraction, transmission electron microscopy and energy dispersive x-ray spectroscopy investigations showed that the nanocrystalline phase was that of Fe-Ni. Grain growth was observed with an increase in the annealing temperature. X-ray photoelectron spectroscopy observations showed the presence of a native oxide layer on the surface of the films. Scanning tunnelling microscopy investigations support the biphasic nature of the nanocrystalline microstructure that consists of a crystalline phase along with an amorphous phase. Magnetic studies using a vibrating sample magnetometer show that coercivity has a strong dependence on grain size. This is attributed to the random magnetic anisotropy characteristic of the system. The observed coercivity dependence on the grain size is explained using a modified random anisotropy model.