ELECTRICAL AND MAGNETIC-PROPERTIES OF LA0.7-XSR0.3MNO3 ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.20) PEROVSKITE AT LOW-TEMPERATURE

Electrical and magnetic properties of La0.7-xYxSr0.3MnO3 (0 less than or equal to x less than or equal to 0.2) have been extensively investi gated at low temperature down to 1.8 K. The irreversibility of magneti c susceptibility between zero field cooling and field cooling increase s with increasing Y content. The metal-insulator transition temperatur e (T-M) shifts towards lower temperature and the peak resistivity and magnetoresistance increase with the increase of x. Electrical conducti on above T-M is dominated by the variable range hopping mechanism. The increase in resistivity at low temperature has been interpreted in te rms of electron-electron interaction. The enhancement of magnetoresist ance with the increase of Y content is due to the reduction in Mn-O-Mn bond angle and the mobility of charge carriers.