The magnetic properties of the hole-doped cobaltites R0.5A0.5CoO₃(R   La, rare earth and A   Ca, Sr, Ba)

The ac and dc magnetic properties of hole-doped cobaltites with compositions La 0.5 Sr 0.5-x A x CoO 3 (A = Ca, Ba) and La 0.5-x R x Sr 0.5 CoO 3 (R = Nd, Eu) have been studied. The suppression of the cluster glass behaviour of the parent compound, La 0.5 Sr 0.5 CoO 3 , by substitutions for either the lanthanum or the strontium ions is accompanied by an increase in coercive field ( H C ) and thermomagnetic irreversibility. The results suggest that the large thermomagnetic irreversibility and coercive fields observed in the hole-doped perovskite cobaltites, arising due to the anisotropic nature of their ferromagnetic character, cannot be correlated with the cluster glass freezing observed in them.