THEORY OF FERROMAGNETISM AND COLOSSAL MAGNETORESISTANCE IN DOPED MANGANITES
THEORY OF FERROMAGNETISM AND COLOSSAL MAGNETORESISTANCE IN DOPED MANGANITES
复制标题
掺杂锰矿的铁磁性和巨磁阻理论
DOI：
10.1063/1.369781
复制
发表时间：
1999
影响因子：
3.2
通讯作者：
A. Bratkovsky
中科院分区：
文献类型：
--
作者：
A. Alexandrov;A. Bratkovsky
在具有强电子-声子耦合的掺杂电荷转移绝缘体中，具有局域自旋的极化子载流子的交换作用导致了一种新的铁磁跃迁。交换和电子-声子相互作用的相对强度决定了跃迁是一级还是二级。在过渡期间，电流载流子数量的巨大下降是顺磁相双极化子形成的结果，对外部磁场极为敏感。我们发现载流子密度塌缩描述了掺杂锰矿石在过渡附近的巨大磁阻、异常比热和隧穿间隙。结合能对离子质量的依赖解释了16O被18O取代后磁化和电阻率的巨大同位素效应。
An exchange interaction of polaronic carriers with localized spins leads to a new ferromagnetic transition in doped charge-transfer insulators with strong electron–phonon coupling. The relative strength of the exchange and electron–phonon interactions determines whether the transition is first or second order. A giant drop in the number of current carriers during the transition, which is a consequence of bipolaron formation in the paramagnetic phase, is extremely sensitive to an external magnetic field. We show that the carrier density collapse describes the colossal magnetoresistance, anomalous specific heat, and tunneling gap of doped manganites close to the transition. The dependence of the binding energy on ion mass explains the giant isotope effect in magnetization and resistivity upon substitution of 16O by 18O.