149Sm nuclear forward scattering of Sm4Bi3 under high pressure

High-pressure 149 Sm nuclear forward scattering experiments have been performed on a mixed valence Sm4Bi3 compound which shows a charge ordering at 260 K. A pressure-induced first- order structural phase transition takes place at 2.3 GPa and 200 K. We present the. first clear experimental evidence that magnetic ordering occurs just above 120K at 3.2 GPa. This magnetic ordering temperature is much higher than that at ambient pressure. The higher magnetic ordering temperature is consistent with the occurrence of a valence change of nonmagnetic Sm (2+) ion toward magnetic Sm (3+) ion at 2.3 GPa. (c) 2006 Elsevier B. V. All rights reserved.