类钙钛矿化合物Ca(Mn_2Cu_1)Mn_4O_(12)的磁性与磁电阻效应

Magnetic properties and colossal magnetoresistance effect in perovskite-type manganite Ca(Mn_2Cu_1)Mn_4O_( 12)

利用固相反应法制备了名义成分为Ca(Mn2 Cu1 )Mn4 O1 2 的类钙钛矿锰氧化物 .x射线衍射表明 ,为了获得较为致密的样品和减小杂相含量 ,可以采用高温烧结再在 10 73K长时间空气中退火的制备方法 .样品在低温下同时存在铁磁相和反铁磁相 ,由于反铁磁相的存在导致样品在 4 5K时的磁化强度显著降低 ,并在 8T的高磁场下仍未达到饱和 .样品呈半导体导电性质 ,在 85K和 6T磁场下磁电阻比的最大值可达 - 4 6 % .

The perovskite-type manganites Ca(Mn 2Cu 1)Mn 4O 12 were prepared using the conventional solid state reaction method. X-ray diffraction patterns show that the annealing in air at 1073 K after the first sintering at higher temperatures can reduce the volumetric percentage of impurity phases in samples. Magnetic measurements indicate that the samples exhibit ferromagnetic-antiferromagnetic transitions at low temperatures. Magnetization of the samples at 4.5 K is greatly decreased due to the existence of the antiferromagnetic phase, and shows no sign of saturation at 4.5 K and a magnetic field up to 8 T. The samples show semiconducting behavior. Their MR ratio reaches -35%—-46% at the temperature of 85 K and the magnetic field of 6 T.