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Phys. Rev. B 52, 12779–12783 (1995)

[Issue 17 – 1 November 1995 ]

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Superparamagnetic relaxation of Fe deposited on MgO(001)

Yongsup Park, S. Adenwalla, G. P. Felcher, and S. D. Bader

Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439

Superparamagnetic behavior is investigated for Fe grown at 700 K onto MgO(001) to a thickness equivalent to that of a ten monolayer film. Two such Fe deposits separated by a 200-Å deposit of MgO exhibit a ferromagnetic response with no hysteresis at either 300 or 150 K, but with identical reduced magnetization curves M(H/T) which confirms the existence of superparamagnetism. M(H) data at 300 K were fitted to a Langevin function to yield an average particle size of 100 Å diameter. M(T) for field-cooled and zero-field-cooled samples shows behavior characteristic of superparamagnetic particles with a distribution in particle size. Time-dependent remanent magnetization data measured over a 20 h period at various temperatures show nonexponential decay attributed to the distribution in particle size and interactions among the particles.

©1995 The American Physical Society

URL: http://link.aps.org/abstract/PRB/v52/p12779
DOI: 10.1103/PhysRevB.52.12779
PACS: 75.30.Pd, 75.50.Rr, 75.70.Cn

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