Magnetic and magnetotransport properties of GdBaCo2O5+δ:: A high magnetic-field study -: art. no. 214401

Magnetic, transport. and optical measurements performed on GdBaCo2O5.5 under pulsed magnetic fields up to 35 T have allowed us to determine its complete mu H-o-T phase diagram. A first-order field-induced transition takes place below the Neel point (T(N)approximate to 255 K) which implies the appearance of a ferromagnetic component and steep changes in the conductivity. The ferromagnetic component (0.45+/-0.1) mu (B)/(Co ion) does not appreciably change below T-N. The nature of the high-field ferromagnetic state is discussed in connection with the zero-field ferromagnetic (or ferrimagnetic) phase above T-N.