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XPS and Magnetization Measurements Study of CrMn Nanoparticles

Published online by Cambridge University Press:  17 March 2011

Wathiq Abdul-Razzaq  and
Unchul Lee
Wathiq Abdul-Razzaq
Affiliation:
Physics Department, West Virginia University, Morgantown, WV 26506, U.S.A.
Unchul Lee
Affiliation:
U.S. Army research Laboratory, Adelphi, MD 20783, U.S.A.
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Abstract

Cr1-xMnx (x < 6.3 %) alloy in the bulk form is an interesting complex system that behaves in many but not all respects like a spin-glass system. In this study, 14 nm-size CrMn nanoparticles with 5% Mn, were synthesized by ball milling of Cr and Mn particles in Ar atmosphere. After 50 hours of milling, the x-ray diffraction pattern indicated alloying of the two metals Cr and Mn. However XPS data indicated the formation of MnO2 and Cr2O3oxides on the surface of the chromium core in the nanoparticle. These oxides on the surface, like the Cr core, are antiferromagnets. Magnetization (M) measurement at 200 G as a function of temperature (T), after zero-field-cooling, showed that M increased as T increased from 5 K all the way to 330 K, beyond the Neel temperatures of the Cr and the oxides. Even though the magnetization value is in the range of a typical antiferromagnet at all temperatures from 5 to 330 K, the shape of M versus T curve is neither that of an antiferromagnet nor of a spin-glass. It appears that the behavior of the magnetization curve is due to the frustration of the spins by weak fields associated with spin-density-wave and by the existence of the oxides. This frustration should be different from the frustration of the spins due to the ferromagnetic-antiferromagnetic competition in spin-glass systems.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 704: Symposium W – Nanoparticulate Materials , 2001 , W9.30.1
Copyright
Copyright © Materials Research Society 2002

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