【摘要】 本文研究了La0 .7Ca0 .3MnO3多晶样品的输运性质、电子顺磁共振 (EPR)谱随温度的变化规律 .实验发现 ,材料电阻率、热电势在居里温度附近各形成一个尖锐的峰 ,而在居里温度上、下有着完全不同的变化规律 ,EPR谱结果也与之完全吻合 .可以认为在居里温度以下双交换作用使eg 电子退局域而减小电阻率 ;而在居里温度以上由Jahn Teller晶格畸变形成的小极化子使eg 电子局域化而增大电阻率 .进而证实是双交换作用和小极化子效应共同导致了CMR效应的出现更多还原

【Abstract】 Temperature dependencies of the transport and the electron paramagnetic resonance (EPR) of La\-\{0.7\}Ca\-\{0.3\}MnO\-3 polycrystalline were studied. A sharp peak was observed in the resistivity as well as in the thermoelectric power curve near the Curie temperature T\-c , and the variations of resistivity and thermoelectric power show completely different behaviors below and above T\-c , which coincide with the EPR results. It can be regarded that the double exchange makes the e\-g electrons delocalize below T\-c , and thus decreases the resistivity; the small polarons induced by Jahn Teller lattice distortion make the e\-g electrons localize above T\-c , and thus increases the resistivity. It is confirmed that the CMR effect originates from both actions of double exchange interaction and small polarons mechanism更多还原