Surface anisotropy and magnetic freezing ofMnOnanoparticles

• DOI: 10.1103/physrevb.75.134423
• Publication Date: 2007-04-26T23:06:41Z
• Authors: M. A. Morales; R. Skomski; S. Fritz; G. Shelburne; J. E. Shield; Ming Yin; Stephen O’Brien; D. L. Leslie-Pelecky
• Keywords: Physics; 530; 01 natural sciences; 0104 chemical sciences

Nanoparticles of bulk antiferromagnets often exhibit ferromagnetic behavior due to uncompensated surface spins. The peak temperature in the zero-field-cooled magnetization of $\mathrm{MnO}$\char22{}in contrast to other antiferromagnetic nanoparticles\char22{}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\char21{}low-spin transition not present in $\mathrm{NiO}$ nanoparticles.