Eur. Phys. J. B 62, 423-431 (2008)
https://doi.org/10.1140/epjb/e2008-00188-7

Nonlinear magnetic response in ruthenocuprates

¹ Institute of Physics, POB 304, 10000 Zagreb, Croatia
² LQM, IPMC, EPFL, 1015 Lausanne, Switzerland
³ National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi, 110012, India
⁴ LPRX, IPMC, EPFL, 1015 Lausanne, Switzerland

Corresponding author: ^a zivkovic@ifs.hr

Received: 19 September 2007
Revised: 10 April 2008
Published online: 22 May 2008

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-xCe_xCu₂O₁₀ 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 μSR and Mössbauer spectroscopy. We find that the spin-spin correlation temperature is the same in both families of ruthenocuprates.