Praseodymium and Copper Magnetism in (Pr_1.5Ce_0.5)Sr_2Cu_2GaO_9

Pr and Cu magnetism in (Pr_1.5Ce_0.5)Sr_2Cu_2GaO₉ are characterized with DC magnetization (M_DC), differential magnetic susceptibility (\chi_d), and x-ray diffraction (XRD) measurements. Weak ferromagnetic (WF) behavior and several cusps in the M_DC data indicate a canted Cu spin structure and multiple Cu spin structure transitions. Analysis of the \chi_d data indicates a Curie-Weiss profile above ~ 30 K, an ordering of the Pr spins below ~ 7K, and a reduced Pr effective moment of 2.79 μ_B. Structural analysis indicates that (Pr_1.5Ce_0.5)Sr_2Cu_2GaO₉ falls into a class of Pr-based high T_C cuprates which shows an uncharacteristically large Pr Nèel temperature and a reduced Pr effective moment, in agreement with the magnetic analysis. The relationship between the structural and magnetic data is discussed and interpreted in terms of current understanding of the behavior of Pr in high T_C materials, particularly the suppression of superconductivity and highly correlated f-electron behavior.