1. Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India;2. Department of Physics, University of Calcutta, Kolkata 700009, India;3. USBAS, Guru Govind Singh Indraprastha University, New Delhi 110403, India
Abstract:
Nanosheets of nickel with thickness equal to 0.6 nm have been grown within the interlayer spaces of Na-4 mica. The sheets are made up of percolative clusters of nanodisks. Magnetization characteristics indicate a superparamagnetic behavior with a blocking temperature of 428 K. The magnetic anisotropy constant as extracted from the coercivity data has been found to be higher than that of bulk nickel by two orders of magnitude. This is ascribed to a large aspect ratio of the nickel nanophase. The Bloch exponent is also found to be considerably different from that of bulk nickel because of a size effect. The Bloch equation is still found to be valid for the two dimensional structures.