Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Phys Rev Lett. 2010 Aug 27;105(9):097203. doi: 10.1103/PhysRevLett.105.097203. Epub 2010 Aug 26.
Large-scale Monte Carlo simulation results for the two-orbital model for manganites, including Jahn-Teller lattice distortions, are presented here. At hole density x=1/4 and in the vicinity of the region of competition between the ferromagnetic metallic and spin-charge-orbital ordered insulating phases, the colossal magnetoresistance (CMR) phenomenon is observed with a magnetoresistance ratio ∼10,000%. Our main result is that this CMR transition is found to be of first order in some portions of the phase diagram, in agreement with early results from neutron scattering, specific heat, and magnetization, thus solving a notorious discrepancy between experiments and previous theoretical studies. The first order characteristics of the transition survive, and are actually enhanced, when weak quenched disorder is introduced.
本文介绍了包含 Jahn-Teller 晶格畸变的锰氧化物双轨道模型的大规模蒙特卡罗模拟结果。在空穴密度 x=1/4 处，在铁磁金属相与自旋电荷轨道有序绝缘相竞争的区域附近，观察到巨磁电阻（CMR）现象，磁电阻比约为 10000%。我们的主要结果是，在相图的某些部分，发现这个 CMR 转变是一级相变，与早期的中子散射、比热和磁化结果一致，从而解决了实验与先前理论研究之间的一个明显差异。当引入弱淬火无序时，相变的一级特征仍然存在，并且实际上得到了增强。
