Study of spin glass and cluster ferromagnetism in RuSr2Eu1.4Ce0.6Cu2O10-δ magneto superconductor

We report DC magnetization, detailed systematic linear and nonlinear AC magnetic susceptibility and transport for a single phase RuSr2Eu1.4Ce0.6Cu2O10-delta (EuRu-1222) magneto-superconductor. The studied sample is synthesized through standard solid state reaction route, which is crystallized in single phase tetragonal structure with space group I4/mmm. DC magnetic susceptibility measurements revealed that the studied EuRu-1222 is a magneto-superconductor with Ru spins ordering at around 110 K and superconductivity in the Cu-O-2 planes below approximate to 30 K. Temperature dependence of AC susceptibility with different frequency and amplitude variations confirms spinglass behavior with cluster ferromagnetism of the system. Change in the cusp position with frequency follows the Vogel-Fulcher law, which is commonly accepted feature for a spin-glass (SG) system with ferromagnetic clusters. The third harmonic of AC susceptibility (chi(3)) shows that the system undergoes a spin glass transition below 80 K. Superconducting transition temperature (T-c) onset and rho = 0 are seen at around 30 and 18 K without any applied field and the same decreases to 10 and 2 K under 130 kOe applied field. Also low fields isothermal (MH) suggests that ferromagnetic clusters are embedded in spin-glass (SG) matrix. The magnetization versus applied field (MH) loops exhibited ferromagnetic (FM) like behavior with rather small coercive fields. Detailed AC magnetic susceptibility measurements are carried out to unearth the short range magnetic correlations. These results support the spin-glass (SG) formation followed by ferromagnetic clustering effects at low temperatures. Our detailed magnetization and magneto transport results will undoubtedly contribute to current understanding of the complex magnetism of the EuRu-1222 system. (C) 2011 American Institute of Physics. [doi:10.1063/1.3626824]