Enhancement of surface magnetization in antiferromagnetic nanoparticles

We report enhancement of magnetization below the antiferromagnetic ordering temperature TNTN in nanoparticles of two antiferromagnets, viz CoRh2O4 and Cr2O3. The enhancement of magnetization below TNTN is systematic, being larger for sample with smaller particle size. Scaling analysis showed that such enhancement of magnetization in CoRh2O4 nanoparticles is due to the superparamagnetic type contribution of surface (shell) spins. The present work shows that similar analysis can also be applied in Cr2O3 nanoparticles.