CORRELATION BETWEEN MAGNETOVOLUME AND GIANT MAGNETORESISTANCE EFFECTSIN DOPED LA2 3CA1/3MNO3 PEROVSKITES/

La0.62Tb0.05Ca0.33MnO3 and La0.6Y0.07Ca0.33MnO3 have been studied in o rder to probe into the mechanisms responsible for the giant magnetores istance ratios observed in this kind of compound. The experiments have shown a strong connection between the magnetotransport and magnetovol ume properties. A large volume effect appears above T-c which collapse s with applied magnetic held or when the long range magnetic order set s in. Above T-c the magnetostriction and magnetoresistance isotherms a re highly correlated. Charge localization with local distortion appear s to be responsible for the transport and volume properties at zero he ld. Charge mobility and a more normal volume dependence on temperature are restored by applying high enough magnetic fields. (C) 1996 Americ an Institute of Physics.