Title: Magnetic properties of nano-sized Co₂FeSi

Authors: K. Venugopalan; Kuntal Kabra; A. Vinesh; N. Lakshmi

Addresses: Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001, Rajasthan, India. ' Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001, Rajasthan, India. ' Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001, Rajasthan, India. ' Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001, Rajasthan, India

Abstract: Nano-sized samples of Co₂FeSi have been synthesised by mechanical alloying using a high energy ball mill. The average crystallite size shows a systematic decrease with milling time. Mössbauer and DC magnetisation studies show that the Co₂FeSi phase is formed at 9 h of milling and is optimised after 12 h of milling. Further milling results in the formation of a superparamagnetic phase with a corresponding deterioration in magnetic properties. A distribution in crystallite size is evident from the co-existence of superparamagnetic doublets with the magnetic hyperfine field in Mossbauer spectra. The presence of a large magnetically dead layer at the surface of the particles makes the value of saturation magnetisation less in the case of the 12 h sample as compared to the bulk. After 24 h of milling, the alloying process is complete but most of the particles of Co₂FeSi are now superparamagnetic.

Keywords: Heusler alloys; nano Co2FeSi; mechanical alloying; magnetic properties; 57Fe Mossbauer; nanotechnology; milling; superparamagnetic doublets.

DOI: 10.1504/IJNT.2011.044432

International Journal of Nanotechnology, 2011 Vol.8 No.10/11/12, pp.877 - 884

Published online: 24 Dec 2011 *

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