Field-dependent magnetic and transport properties and anisotropic magnetoresistance in ceramic La_0.67Pb_0.33MnO₃

Abstract

A summary of detailed measurements of the field and temperature dependence of the ac susceptibility, magnetization and the longitudinal and transverse magnetoresistivities of ceramic La0.67Pb0.33MnO3 is presented. Detailed analysis of the magnetic data provides an estimate of 340.5±0.5 K for the paramagnetic to ferromagnetic transition temperature Tc, with the data closest to the critical point yielding = 1.39±0.06 (from the temperature dependence of the susceptibility along the crossover line), = 0.41±0.02 (from the field induced variation of the temperature of the same line) and = 4.20±0.15 (from the field dependence of the critical isotherm). Nevertheless the presence of disorder - a variance in the distribution of spin-spin coupling strengths - means that Heisenberg model (asymptotic) exponents cannot be excluded; the universality class for this system cannot therefore be definitively identified.