Eur. Phys. J. B 53, 307-313 (2006)
https://doi.org/10.1140/epjb/e2006-00393-4

Magnetization scaling in the ruthenate-cuprate RuSr₂Eu_1.4Ce _0.6Cu₂O_10-δ (Ru-1222)

¹ Instituto de Física, Universidade Federal do Rio de Janeiro, C.P. 68528, RJ, 21941-972, Brazil
² Laboratorio de Superconductividad, Facultad de Física-IMRE, Universidad de La Habana, San Lázaro y L, Ciudad de La Habana, 10400, Cuba
³ Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel

Corresponding author: ^a sgargar2000@yahoo.com.br

Received: 30 May 2006
Revised: 6 September 2006
Published online: 27 October 2006

Abstract

The magnetic properties of the superconducting ruthenate-cuprate RuSr₂Eu _1.4Ce_0.6Cu₂O_10-δ (Ru-1222) have been studied by a scaling analysis of the dc magnetization and ac susceptibility measurements. Non-linear M(H) curves reveal the presence of nano-size clusters with a net magnetic moment of ∼10² μ_B at 180 K, near the deviation from a Curie-Weiss behavior. On cooling, no scaling was observed down to 90 K, discarding the possibility of magnetic phase separation of collinear ferromagnetic particles. We explain this result in terms of a variable number of contributing particles, with a temperature dependent net magnetic moment. For 70 K ≤T≤ 90 K the scaling plots evidence the emergence of a system of non-interacting particles, which couple on further cooling. The observed cluster-glass features are preserved down to the lowest measured temperature (10 K); no signature of long-range order was detected. The frequency shift of the peak in the real part of the ac susceptibility does not follow the Vogel-Fulcher type dependence, as previously reported. The puzzling temperature dependence of the coercive field, H_C(T), is correlated with the changes in the scaling factors.