THERMOELECTRIC-POWER, SPECIFIC-HEAT, AND GIANT MAGNETORESISTANCE OF LA0.85MNO3

Magnetization, thermoelectric power (TEP), specific heat (C-p), and ma gnetoresistance (MR) of the as prepared (AP) and oxidized (OX) polycry stalline La0.85MnO3 are reported. Both the samples have rhombohedral s ymmetry. The magnetization of the OX sample showed a sharper rise as a function of temperature with a T-c similar to 270 K and a well define d peak of C-p close to T-c. The TEP of the AP sample was positive betw een 10<T<300 K with a maximum located near T-c, but the OX sample show ed a negative value between 240 and 300 K. A maximum of 75% in MR was observed for the OX sample in a field of 5 T at 270 K. The data were a nalyzed in light of similar data obtained on divalent (Sr,Ca) substitu ted LaMnO3 and the existing models. (C) 1998 American Institute of Phy sics.