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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.45  No.7 (2004)  >  pp.2012-2017

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HRTEM and EELS Studies of L10-Ordered FePt nano-Clusters on MgO Films Prepared Below 673 K

Shunsuke Fukami1), Akichika Ohno1) and Nobuo Tanaka1)2)
1) Department of Crystalline Materials Science, Nagoya University
2) EcoTopia Science Institute, Nagoya University

Three kinds of FePt-MgO granular films were prepared by a vacuum successive deposition of MgO, Pt, Fe and MgO on a cleaved surface of sodium chloride below 673 K. Their microstructures, electronic structures and magnetic properties were studied by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS) and measurement with a superconducting quantum interference device (SQUID) magnetometer. The TEM observations and selected area electron diffraction patterns revealed that the samples mainly consist of few nm-sized FePt clusters embedded in MgO films with L10-ordered structure and c-axis perpendicular to the film surface. Size effect on the stability of L10 phase in the FePt nano-clusters was directly observed in [MgO/Fe(0.38 nm)/Pt(0.30 nm)/MgO] and the critical size of the transition from L10 to A1 phase was estimated as around 2 nm, that can be considered as smaller than effective size for the transition from ferromagnetism to superparamagnetism. Coercivity of [MgO/Fe(1.0 nm)/Pt(0.8 nm)/MgO] was 1.2 × 105 A/m. The Fe-L2,3 white-line ratios of the present samples measured by EELS were about 4.0, independently on the incident direction of electron beam. The higher white-line ratio may be attributed to their high-spin state by a change of 3d-band structure owing to the hybridization of d-bands between Fe and Pt atoms.

perpendicular magnetic recording media, L10-iron platinum, nano-cluster, high-resolution transmission electron microscopy, electron energy-loss spectroscopy, size-effect, low temperature preparation, magnesium oxide, white-line ratio

Received: January 19, 2004
Accepted: March 10, 2004 , Published online: June 24, 2005
Copyright (c) 2005 The Japan Institute of Metals



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