Effects of Localized Holes on Charge Transport, Local Structure, and Spin Dynamics in the Metallic State of CMR La_(1-x)Ca_xMnO_3

摘要

We review resistivity, x-ray-absorption fine-structure (XAFS) and muon spin relaxation (#mu#SR) datawhich provide clear evidence for localized holes causingpolaron distortion and unusual spin dynamics below T_c in"colossal magnetoresistive" (CMR) La_(1-x)Ca_xMnO_3.Resistivity measurements for x=0.33 under an applied field Hhave shown that ln(#rho#(H,T)) Propor.to-M; where M is themagnetization. The XAFS data show a similar functionaldependence for the polaron distortions on M. The data fromthese two measurements are interpreted in terms of somefraction of the available holes x remaining localized and someincreasing fraction becoming delocalized with increasing M.Finally, this polaron-induced spatial inhomogeneity yieldsanomalously slow, spatially inhomogeneous spin dynamicsbelow T_c, as shown in the #mu# SR data. These experimentsindividually probe the charge, lattice and spin degrees offreedom in this CMR system and suggest that the polarons retainsome identity even at temperatures significantly below T_c.