Evidence for magnetic clusters in Ba Co O 3

Magnetic properties of the transition metal oxide $\mathrm{Ba}\mathrm{Co}{\mathrm{O}}_{3}$ are analyzed on the basis of the experimental and theoretical literature available via ab inito calculations. These can be explained by assuming that the material is formed by noninteracting ferromagnetic clusters of about $1.2\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ in diameter separated by about 3 diameters. Above about $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the so-called blocking temperature, superparamagnetic behavior of the magnetic clusters occurs and, above $250\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, paramagnetism sets in.