Reentrant spin glass transition in La$_{0.96-y}$Nd$_{y}$K$_{0.04}$MnO$_3$: origin and effects on the colossal magnetoresistivity

摘要

Magnetic, electric and structural properties ofLa$_{0.96-y}$Nd$_y$K$_{0.04}$MnO$_{3+\delta}$ with 0$\leq y \leq$0.4 have beenstudied experimentally. A disordered magnetic state is formed as La issubstituted by Nd, reflecting the competition between ferromagnetic (FM) doubleexchange and antiferromagnetic superexchange interactions. Key structuralparameters are identified and correlated with changes in magnetic and electricproperties. By application of a large magnetic field, spin disorder scatteringis removed, creating a new magnetoresistance peak at a temperature lower thanthe first near-$T_c$ peak. Time dependent zero-field-cooled magnetisationmeasurements have been performed for $y$=0.4 around this temperature. Areentrant spin glass (RSG) transition is evidenced, with low field ageingproperties in both the RSG and FM phases, similar to those observed inarchetypal spin glass materials.