Coexistence of ferromagnetism and cluster glass state in superconducting ferromagnet RuSr_2Eu_(1.5)Ce_(0.5)Cu_2O_(10-delta)

摘要

Systematic dc and ac magnetic susceptibility measurements performed on RuSr_2Eu_(1.5)Ce_(0.5)Cu_2O_(10-delta) (Ru1222) demonstrate a paramagnetic to ferromagnetic transition around 95 K. The third harmonic of the ac susceptibility reveals that the system undergoes a spin glass transition below 75 K. The features of the zero-field cooled and field cooled dc magnetization curves of Ru1222 material resemble those of a cluster glass state, rather than those of a canonical spin glass state. The magnetization versus applied field loops do not saturate, even at very high applied fields, resulting in the short range magnetic order in the system, which facilitates the formation of clusters that freeze at low temperature. The temperature dependence of the second and third harmonic ac susceptibilities further confirms the coexistence of a cluster glass state and ferromagnetic order in the Ru 1222 system.