MAGNETOSTRICTION AND THERMAL-EXPANSION ANOMALIES NEAR THE CURIE-POINTOF THE COMPOUND LA0.7SR0.3MNO3 WITH THE PEROVSKITE STRUCTURE

It is found that the bulk part omega of the magnetostriction near the Curie temperature T-c in a La0.7Sr0.3MnO3 single crystal with the pero vskite structure is negative and that the temperature dependence of /o mega/ has a maximum near T-c. The quantity /omega/ at the maximum incr eases rapidly with increasing magnetic field. The thermal expansion co efficient near T-c increases with temperature much Easter than linearl y. The paramagnetic Curie temperature determined from the Curie-Weiss law, which the paramagnetic susceptibility of this crystal satifies, w as found to be lower than T-c. These anomalies and also the near-T-c m etal-insulator transition which is characteristic for this material ar e explained by the existence of a magnetically two-phase state consist ing of a conducting ferromagnetic matrix containing antiferromagnetic insulating microregions occupying not more than 5% of the sample volum e. (C) 1997 American Institute of Physics.