钙钛矿锰氧化物La0.7Sr0.3MxMn1-xO3(M=Cr,Fe)的巨磁电阻效应与磁性

研究了溶胶-凝胶法制备氧化物巨磁电阻材料的工艺，制备了La_0.7Sr_{0.3< /sub>CrxMn1-xO3(x=0,0.10,0.15)和La0.7Sr0.3FexMn1-xO3(x=0.05,0.10,0.16)两 系列的单相钙钛矿锰氧化物多晶样品，并研究了Cr，Fe替代La0.7Sr0.3MnO3中部分Mn后对其结构、磁性和巨磁电阻性质的影响.观察到La0.7 Sr0.3Cr0.15Mn0.85O3和La0. 7Sr0.3Fe0.05Mn0.95O3两个样品的 电阻-温度曲线都出现了双峰.定性讨论了可能产生双峰的机制.随Cr(或Fe)替代量的增加， 材料的居里温度很快下降，铁磁性减弱，导电性降低，巨磁电阻效应增强.但与Fe掺杂相比 ，相同数量的Cr掺杂对材料的影响要小. 关键词： 巨磁电阻效应 溶胶-凝胶工艺 电阻-温度曲线 金属绝缘体转变}

COLOSSAL MAGNETORESISTANCE EFFECTS AND MAGNETIC PROPERTIES OF La0.7Sr 0.3MxMn1-xO3 (M=Cr,Fe)

This paper discusses the preparation of the colossal magnetoresistance samples L a_0.7Sr_0.3Cr_xMn_1-xO₃ (x=0, 0.10, 0.15) and La_0.7Sr_0.3Fe_xMn_1-xO ₃ (x=0.05,0.10,0.16) by the sol-gel technique. The effects that the s ubstitution of Cr or Fe for Mn in La_0.7Sr_0.3MnO₃ affects its structure, magnetic properties and magnetoresistance are also stud ied. Two peaks are observed on the resistance-temperature curves (R-T curves) of the two samples La_0.7Sr_0.3Cr_0.15Mn_{0.85O3 and La0.7Sr0.3Fe0.05Mn0.9 5O3. The mechanism for the potential appearance of the double p eaks is discussed. A conclusion is drawn that with the increase of Cr (or Fe) s ubstituting for Mn, the samples' Curie temperature (TC), ferromagnetism and conductivity decrease， whereas their magnetoresistance strengthens. However, t he same amount of Cr produces less effect on the samples than the same amount of Fe.}