Coexistence of Griffiths phase and superparamagnetic-like behavior in La-doped antiferromagnetic CaMnO3

The coexistence of a Griffiths phase and superparamagnetic-like short range interaction in a single-phase homogeneous manganite is of particular interest because it reveals multiple levels of magnetic clustering generated by disorder and competing exchange interactions. In bulk La 0.19 Ca 0.81 MnO 3 , this unusual magnetic state develops in the antiferromagnetic regime, where A-site disorder strongly modifies the local magnetic landscape. Rietveld analysis confirms a single-phase orthorhombic structure, while magnetic measurements establish a Griffiths phase below T G = 280 K through the deviation from Curie–Weiss behavior. Superparamagnetic- like behavior persisting from 280 to 370 K further indicates that isolated magnetic clusters remain stable well into the nominally paramagnetic region. The presence of both phenomena highlights the crucial role of disorder-induced exchange randomness in stabilizing complex magnetic states in correlated perovskite oxides.