Prasankumar R P, Okamura H, Imai H, Shimakawa Y, Kubo Y, Trugman S A, Taylor A J, Averitt R D
Los Alamos National Laboratory, New Mexico 87545, USA.
Phys Rev Lett. 2005 Dec 31;95(26):267404. doi: 10.1103/PhysRevLett.95.267404. Epub 2005 Dec 23.
Optical-pump midinfrared probe spectroscopy is used to investigate coupled charge-spin dynamics in the magnetoresistive pyrochlore TI(2)Mn(2)O(7). We find that the temporal persistence of the photoexcited carrier density is strongly influenced by spin disorder above and below the ferromagnetic Curie temperature. Our results are consistent with a picture whereby spin disorder leads to spatial segregation of the initially excited Tl 6s-O 2p electron-hole pairs, effectively reducing the probability for recombination. This further implies that colossal magnetoresistance in these materials may be driven primarily by Mn t(2g) spin disorder.
光泵浦中红外探测光谱用于研究磁阻焦绿石TI(2)Mn(2)O(7)中的耦合电荷-自旋动力学。我们发现，光激发载流子密度的时间持续性在铁磁居里温度上下受到自旋无序的强烈影响。我们的结果与这样一种图景一致，即自旋无序导致最初激发的Tl 6s-O 2p电子-空穴对的空间分离，有效地降低了复合概率。这进一步意味着这些材料中的巨磁阻可能主要由Mn t(2g)自旋无序驱动。
