Particle size effects in the antiferromagnetic spinel CoRh$_2$O$_4$
  We report the particle size dependent magnetic behaviour in the antiferromagnetic spinel CoRh2O4. The nanoparticles were obtained by mechanical milling of bulk material, prepared under sintering method. The XRD spectra show that the samples are retaining the spinel structure. The particle size decreases from 70 nm to 16 nm as the milling time increases from 12 hours to 60 hours. The magnetic measurements suggest that the antiferromagnetic ordering at T$_N$ $\approx$ 27K exists in bulk as well as in nanoparticle samples. However, the magnitude of the magnetization below T$_N$ increases with decreasing particle size. 
R.N. Bhowmik, R. Nagarajan and R. Ranganathan