Magnetic states and spin-glass properties in Bi0.67Ca0.33MnO3: macroscopic ac measurements and neutron scattering

We report on the magnetic properties of the manganite Bi_{1-x}Ca_{x}MnO_3 (x=0.33) at low temperature. The analysis of the field expansion of the ac susceptibility and the observation of aging properties make clear that a spin glass phase appears below T = 39K, in the presence of magnetic order. Neutron scattering shows both magnetic Bragg scattering and magnetic diffusion at small angles, and confirms this coexistence. In contrast to Pr_{1-x}Ca_{x}MnO_3 (x=0.3-0.33) which exhibits a mesoscopic phase separation responsible for a field driven percolation, the glassy and short range ferromagnetic order observed here does not cause colossal magnetoresistance (CMR).