Nonlinear magnetic response in ruthenocuprates

TL;DR

This study investigates the nonlinear magnetic response in ruthenocuprates, revealing complex magnetic transitions, effects of doping, and correlations between different ruthenocuprate families through harmonic analysis.

Contribution

It provides new insights into the magnetic behavior and transitions in ruthenocuprates using nonlinear response measurements, highlighting effects of doping and magnetic ordering.

Findings

Identification of a diverging peak at T_N indicating canted antiferromagnetism.

Observation of superparamagnetic particle blocking above T_N.

Correlation of magnetic transition temperatures across ruthenocuprate families.

Abstract

We have performed an investigation of the nonlinear magnetic response in ruthenocuprates. A negative, diverging-like peak at the main magnetic transition T_N in RuSr2RECu2O8 (RE = Gd, Y) indicates a possible canted antiferromagnetic order. Another well defined feature above T_N points to a blocking of superparamagnetic particles through the T^(-3) dependence of the third harmonic at higher temperatures. Below T_N a nondiverging peak appears, which is strongly affected by the addition of 10% of Cu ions in the RuO2 planes. In RuSr2RE(2-x)Ce(x)Cu2O10 the main magnetic transition T_M is accompanied by two characteristic temperatures in the third harmonic of the ac susceptibility, in agreement with recent studies from uSR and Mossbauer spectroscopy. We find that the spin-spin correlation temperature is the same in both families of ruthenocuprates.