Spin-polarized transport and magnetoresistance in magnetic oxides
Spin-polarized transport and magnetoresistance in magnetic oxides
复制标题
DOI：
10.1016/s0304-8853(99)00373-x
复制
发表时间：
1999-10
影响因子：
2.7
通讯作者：
Arunava Gupta;Jonathan Z. Sun
中科院分区：
文献类型：
--
作者：
Arunava Gupta;Jonathan Z. Sun
具有高度自旋极化的磁性氧化物材料被发现具有增强的自旋相关输运性质。例如，钙钛矿型锰氧化物La1−xAxMnO3中的自然晶界或人工晶界所产生的界面会在低场下产生大的磁阻(MR)。在其他导电磁性氧化物中，如二氧化铬(CrO2)、焦绿石Tl2Mn2O7、磁铁矿(Fe3O4)和有序双钙钛矿Sr2FeMoO6中也有非本征晶界MR的报道。在x=0.3时，层状锰氧化物La2−2xSr1+2xMn2O7在低场下的电阻变化更大，它在c轴方向上具有自然的隧道结结构。但是，到目前为止，在薄膜铁磁/绝缘/铁磁隧道结结构中观察到了最大的MR效应，据报道，在低场下，锶掺杂的钙钛矿型锰氧化物的电阻变化高达10倍。在大多数情况下，在这些磁性氧化物中增强的MR效应仅限于相当低的温度，并且随着温度的升高而迅速减弱。随着对这些交界处边界性质的更好的理解，在更高的温度下增强MR是可能的。
Magnetic oxide materials possessing a high degree of spin polarization have been found to exhibit enhanced spin-dependent transport properties. For example, interfaces created by naturally occurring or artificial grain boundaries in the perovskite manganites, La1−xAxMnO3, result in a large magnetoresistance (MR) at low fields. Extrinsic grain boundary MR has also been reported in other conducting magnetic oxides, such as chromium dioxide (CrO2), pyrochlore Tl2Mn2O7, magnetite (Fe3O4), and the ordered double-perovskite Sr2FeMoO6. Even larger changes in resistances at low fields are obtained in the layered manganite, La2−2xSr1+2xMn2O7for x=0.3, which possesses a natural tunnel junction structure in the c-axis direction. But, by far, the largest MR effect to date has been observed in thin film ferromagnetic/insulating/ferromagnetic tunnel junction structures, where resistance changes as high as a factor of 10 at low fields has been reported for the strontium-doped perovskite manganites. In most cases, the enhanced MR effect in these magnetic oxides is limited to rather low temperatures and decreases rapidly with increasing temperature. With a better understanding of the nature of the boundaries in these junctions, it might be possible to enhance the MR at higher temperatures.