Mathieu R, Akahoshi D, Asamitsu A, Tomioka Y, Tokura Y
Spin Superstructure Project (ERATO-SSS), JST, AIST Central 4, Tsukuba 305-8562, Japan.
Phys Rev Lett. 2004 Nov 26;93(22):227202. doi: 10.1103/PhysRevLett.93.227202. Epub 2004 Nov 22.
The magnetic and electrical properties of high-quality single crystals of A-site disordered (solid solution) Ln0.5Ba0.5MnO3 are investigated near the phase boundary between the spin-glass insulator and colossal-magnetoresistive ferromagnetic metal, locating near Ln=Sm. The temperature dependence of the ac susceptibility and the x-ray diffuse scattering of Eu0.5Ba0.5MnO3 are analyzed in detail. The uniformity of the random potential perturbation in Ln0.5Ba0.5MnO3 crystals with a small bandwidth yields, rather than the phase separation, an homogeneous short ranged charge or orbital order which gives rise to a nearly atomic spin-glass state. Remarkably, this microscopically disordered "charge-exchange-glass" state alone is able to bring forth the colossal magnetoresistance.
研究了A位无序（固溶体）Ln0.5Ba0.5MnO3高质量单晶在自旋玻璃绝缘体与巨磁阻铁磁金属之间的相界附近（该相界位于Ln = Sm附近）的磁学和电学性质。详细分析了Eu0.5Ba0.5MnO3的交流磁化率和X射线漫散射的温度依赖性。具有小带宽的Ln0.5Ba0.5MnO3晶体中随机势扰动的均匀性产生的是均匀的短程电荷或轨道有序，而非相分离，这种有序导致了近乎原子级的自旋玻璃态。值得注意的是，仅这种微观无序的“电荷交换玻璃”态就能产生巨磁阻。
