The paramagnetic properties of (formula presented) (formula presented) single-crystal perovskites have been studied. The effective moments (formula presented) obtained from fits to the Curie-Weiss law in the paramagnetic regime are strongly enhanced from their theoretical values, both above and below the pseudocubic orthorhombic (formula presented) Jahn-Teller (JT) transition. This indicates the presence of clusters and that this clustering is not induced or affected by the JT transition. The (formula presented) values in the O and (formula presented) phases are very similar, however, their paramagnetic Curie temperatures are rather different, implying that the JT distortion only induces a change in the exchange-coupling parameters but not in the character of the clusters. The correlation between the high-temperature paramagnetic and low-temperature ferromagnetic parameters suggests that the O and (formula presented) phases are not only analogous structurally but have also comparable exchange-coupling parameters and are consequently similar magnetically. Finally, the competition between the JT distortion, the magnetic field, and the molecular field, among other factors, apparently governs the properties of these systems. © 2001 The American Physical Society.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 Jan 2001|