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.