Magnetic Transitions and Ferromagnetic Clusters in RuSr2(Eu,Ce)2Cu2O10+d

TL;DR

This study investigates the complex magnetic behavior of RuSr2(Eu,Ce)2Cu2O10+d, revealing phase separation with superparamagnetic clusters, antiferromagnetic matrix transition, and ferromagnetic ordering, through detailed magnetization measurements.

Contribution

It provides new insights into the phase separation and magnetic transitions in RuSr2(Eu,Ce)2Cu2O10+d, highlighting the coexistence of different magnetic states.

Findings

Identification of superparamagnetic clusters below T_1

Antiferromagnetic transition of the matrix at T_AM

Ferromagnetic transition at T_M with long-range order

Abstract

The macroscopic magnetizations of a RuSr2(Eu0.7Ce0.3)2Cu2O10+d sample were investigated. A ferromagnet-like transition occurs around T_M in the low-field magnetization. Highly nonlinear M(H), non-Curie-Weiss susceptibility, and slow spin-dynamics, however, were observed up to T_1 approx 2-3 T_M. In addition, an antiferromagnet-like differential-susceptibility maximum of Ru appears around a separate temperature T_AM between T_1 and T_M. The data are therefore consistent with a phase-separation model: superparamagnetic clusters (or short-range spin-orders) are first precipitated from the paramagnetic matrix below T_1, followed by an antiferromagnetic transition of the matrix at T_AM and an apparent ferromagnetic (FM) transition around T_M, where the long-range spin-order is established in the FM species imbedded in the matrix.