Mn基钙钛矿样品相图修正及庞磁电阻起因

Correction of the phase diagram of temperature versus A-site ionic size in Mn-based AMnO_3-type perovskite manganites

对具有不同A位平均离子尺寸的AMnO3型Mn基钙钛矿样品的阻温关系和电子顺磁共振谱等进行了实验研究.结果表明,在温度与A位平均离子尺寸的相图上,除了普遍公认的高温顺磁绝缘体相和低温长程铁磁有序的金属相外,在两相之间还存在一过渡相,其起因源于顺磁绝缘体背景上出现短程铁磁有序的金属集团所致.研究结果还表明,外加磁场加速铁磁金属集团的生成和长大是导致庞磁电阻效应的主要原因.

The temperature versus A-site average ionic size phase diagram was corrected basecd on measurements of resistively and electron paramagnetic resonance as functions of temperature for Mn-based AMnO3type perovskite manganite with different A-site average ionic sizes. The results showed that besides two phases, high-temperature paramagnetic insulating and low-temperature ferromagnetic metallic phases, there is a transition phase between them due to the segregation of ferromagnetic metallic clusters in the paramagnetic insulating matrix, it is further argued that the colossal magnetoresistance observed in Mn-based perovskite manganites originates from the application of magnetic field that accelerates generation and growth of ferromagnetic metallic clusters.