Eur. Phys. J. B (2012) 85: 238
https://doi.org/10.1140/epjb/e2012-30075-5

Regular Article

Successive spin glass, cluster ferromagnetic, and superparamagnetic transitions in RuSr₂Y_1.5Ce_0.5Cu₂O₁₀ complex magneto-superconductor

¹ Quanatum Phenomena and Application Division, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, 110012 New Delhi, India
² Department of Physics and Astrophysics, University of Delhi, North Campus, 110007 New Delhi, India

^a e-mail: awana@mail.nplindia.ernet.in

Received: 30 January 2012
Received in final form: 12 April 2012
Published online: 9 July 2012

Abstract

We report structural, DC magnetization, detailed linear/non-linear AC susceptibility, (with applied frequency and amplitude) isothermal and thermoremanent magnetization (TRM) behavior for RuSr₂Y_1.5Ce_0.5Cu₂O₁₀ (YRu-1222) magneto-superconductor to understand its complex magnetism. Studied sample is synthesized through the novel solid state high pressure (6 GPa) high temperature (1450 °C) (HPHT) technique. The compound is crystallized in tetragonal structure with space group I4/mmm (No. 139). DC magnetic susceptibility shows that studied YRu-1222 is magneto-superconducting with Ru spins magnetic ordering at around 110 K and superconductivity (SC) in the Cu-O₂ planes below  ~ 30 K. Frequency and field dependent detailed AC magnetic susceptibility measurements confirms the spin-glass (SG) behavior with homogeneous/non-homogeneous ferromagnetic (FM) clusters in this system. Variation of cusp position with applied AC frequency follows the famous Vogel-Fulcher law, which is commonly accepted feature for spin-glass (SG) system with homogeneous/non-homogeneous ferromagnetic clusters embedded in spin-glass (SG) matrix. Above the freezing temperature (T_f), first and third harmonics AC susceptibility analysis indicated possibility of the co-existence of spin cluster ferromagnetism with superparamagnetism (SPM). The M-H loops at low temperature exhibit the ferromagnetic behavior with rather small coercive field (H_c) and remnant magnetization (M_r). Summarily, the magnetic (DC and AC) susceptibility measurements and their analysis have enabled us to unearth the complex magnetism in terms of successive SG-FM-SPM transitions with temperature.