Surface anisotropy and magnetic freezing of MnO nanoparticles

Authors

Marco Morales Torres, University of Nebraska - LincolnFollow
Ralph Skomski, University of Nebraska-LincolnFollow
Shannon Fritz, University of Nebraska - LincolnFollow
G. Shelburne, University of Nebraska - Lincoln
Jeffrey E. Shield, University of Nebraska - LincolnFollow
Ming Yin, Columbia University, New York City, New York
Stephen O'Brien, Columbia University, New York City, New York
Diandra Leslie-Pelecky, University of Nebraska -- LincolnFollow

Date of this Version

4-26-2007

Comments

Published by American Physical Society. Phys. Rev. B 75, 134423 2007. http://prb.aps.org. Copyright © 2007 American Physical Society. Permission to use.

Abstract

Nanoparticles of bulk antiferromagnets often exhibit ferromagnetic behavior due to uncompensated surface spins. The peak temperature in the zero-field-cooled magnetization of MnO—in contrast to other antiferromagnetic nanoparticles—has anomalous behavior, shifting to higher temperatures with decreasing nanoparticle size. We attribute this behavior to surface anisotropy enhanced by the specific occupancy of 3d levels in Mn, which produces a high-spin–low-spin transition not present in NiO nanoparticles.