The impact of niobium doping upon the magnetotransport properties of the   oxygen-deficient perovskite SrCo1-xNbxO3-d
  The oxygen-deficient perovskite cobaltite SrCo1-xNbxO3-d was synthesized by direct solid-state reaction and its magnetotransport properties were investigated. This cobaltite exhibits an unusual ferromagnetic behavior with a transition temperature Tm = 130-150 K and a spin glass like behavior below Tm. Importantly, this phase reaches a large magnetoresistance (MR) value, MR = -(rH - r0) / r0 = 30% at 5 K in 7 T. The large MR effect is believed to be related to the disordered magnetic state induced by the Nb-for-Co substitution. 
T. Motohashi, V. Caignaert, V. Pralong, M. Hervieu, A. Maignan, and B.   Raveau