Evidence for magnetic polarons in the magnetoresistive perovskites
Evidence for magnetic polarons in the magnetoresistive perovskites
复制标题
DOI：
10.1038/386256a0
复制
发表时间：
1997-03-20
期刊：
影响因子：
64.8
通讯作者：
Arnold, Z
中科院分区：
文献类型：
--
作者：
DeTeresa, JM;Ibarra, MR;Arnold, Z
基于化合物 LaMnO3 的锰钙钛矿凭借其不同寻常的磁和电子特性吸引了相当多的理论和技术兴趣 (1-4)。这些特性中最值得注意的是，随着磁场的应用，电阻率会发生极大的变化，这种效应被称为“巨大”磁阻。这种效应的起源被归因于(5-7)磁极化子的存在——电荷载流子伴随着周围晶格的局域化(和磁极化)畸变(8,9)——但它们的存在和性质仍然是推测的问题。在这里，利用体积热膨胀(有和没有施加场)、磁化率和小角中子散射测量的组合，我们提供了在铁磁有序温度T-c之上存在磁极化子的证据。我们检测到在 T-c 上方自发形成类似于 12 埃的局部磁簇，在施加磁场时，其尺寸会增大，但数量会减少。我们认为，这些磁极化子对施加磁场的响应是化合物 (La(1-x)A(x))(2/3)Ca1/3MnO3（其中 A 是 Y 或 Tb）中显着磁阻特性的基础。
Manganese perovskites based on the compound LaMnO3 are attracting considerable theoretical and technological interest by virtue of their unusual magnetic and electronic properties(1-4). Most notable of these properties is the extremely large change in resistivity that accompanies the application of a magnetic field, an effect known as 'colossal' magnetoresistance. The origin of this effect has been attributed(5-7) to the presence of magnetic polarons-charge carriers accompanied by a localized (and magnetically polarized) distortion of the surrounding crystal lattice(8,9)-but their existence and properties remains a matter of speculation, Here, using a combination of volume thermal expansion (with and without an applied field), magnetic susceptibility and small-angle neutron scattering measurements, we present evidence for the existence of magnetic polarons above the ferromagnetic ordering temperature, T-c. We detect the spontaneous formation of localized similar to 12-Angstrom magnetic clusters above T-c which, on application of a magnetic field, grow in size but decrease in number. We argue that the response of these magnetic polarons to an applied magnetic field underlies the pronounced magnetoresistive properties in the compounds (La(1-x)A(x))(2/3)Ca1/3MnO3 (where A is Y or Tb).