Effects of locatized holes on charge transport, local structure and spin dynamics in the metallic state of CMR La_(1-x)Ga_xMnO_3

摘要

We review resistivity, x-ray-absorption fine-structure (XAFS) and muon spin relaxation ( mu SR) data which provide clear evidence for localized holes causing polaron distortion and unusal spin dynamics below T_C in "colossal magnetoresistive" (CMR) La_(1-x)Ga_xMnO-3. Resistivity measurements for x chemical bounds 0.33 under an applied field H have shown that In[ rho (H, T)] propor.to -M, where M is the magnetization. The XAFS data show a similar functional dependence for the polaron distortions on M. The data from these two measurements are interpreted n terms of some fraction of the vailable holes x remaining localized and some increasing fraction becoming delocalized with increasing M. Finally, this polaron-induced spatial inhomogeneity yeids anomalously slow, spatially inhomogeneous spin dynamics below T_C, as shown in the mu SR data. These experiments individually probe the charge, lattice and spin degrees of freedom in this CMR system and suggest that the polarons retain some identity even at temperatures significantly below T_C.