Magnetic properties of the layered cobaltite NdBaCo2O5.50

We present a DC magnetization, zero and longitudinal field mu SR investigation on the magnetic properties of NdBaCo2O5.50. It was found that NdBaCo2O5.50 exhibits successive magnetic transitions from a high temperature paramagnetic phase to a ferromagnetic (FM) phase at T-C = 290(5) K, then to an antiferromagnetic (AF1) phase at T-N1 = 265(5) K, and to another AF (AF2) phase at T-N2 = 160(10) K. Even though the transition temperatures are similar to the ones of RBaCo2O5.5 with R = Ho, Y, Dy, Th, the microscopic magnetic nature of NdBaCo2O5.50 is very different from the other compounds. That is, the FM phase is characterized by a temperature dependent mixture of dynamic and static phase volumes. The observed mu SR frequencies indicate that in the AFM phases different spin state ordered (SSC) magnetic structures are present in NdBaCo2O5.50 than in the compounds with other rare earth ions. (c) 2008 Elsevier B.V. All rights reserved.