Negative magnetoresistance in La(0.6)Y(0.1)Ca(0.3)MnO(3): Evidence for charge localization governed by the Curie-Weiss law

Abstract

Colossal negative magnetoresistance Δρ(T,B) observed in La(0.6)Y(0.1)Ca(0.3)MnO(3) at B=1T shows a nearly perfect symmetry around T_0=160K suggesting a universal field-induced transport mechanism in this material. Attributing this symmetry to strong magnetic fluctuations (triggered by the Y substitution and further enhanced by magnetic field, both above and below the field-dependent Curie temperature T_C(B)=T_0), the data are interpreted in terms of the nonthermal spin hopping and magnetization M dependent charge carrier localization scenario leading to Δρ(T,B)= -ρ_s(1-exp(-γM^2)) with M(T,B)=CB/|T-T_C|^n. The separate fits through all the data points above and below T_C yield C^{+}\simeq C^{-} and n^{+}\simeq n^{-}\simeq 1. The obtained results corroborate the importance of fluctuation effects in this material recently found (cond-mat/9812219) to dominate its magneto-thermopower behavior far beyond T_C.

4 pages (REVTEX), 2 PS figures (epsf.sty); submitted to Phys.Rev.B