Charge and magnetic ordering in mixed valence system Am_4(Bi_(1-x)Sb_x)_3

摘要

The mixed valence compound Am_4Bi_3 shows the charge ordered state of Am~(2+) and Am~(3+) with a ratio of 3 : 1 and its behavior is similar to that of well-known compound B_4As_3. The main interest in Am_4Bi_3 is a pressure-induced iso-structural transition from a mixed valence state to a trivalent state, in which physical properties are very similar to that of Am_4Sb_3. To reproduce the high-pressure phase, we synthesized and investigated Am_4(Bi_(1-x)Sb_x)_3 system. With increasing Sb content, the carrier concentration decreases and the charge ordering temperature slightly increases, while by applying pressure the ordering temperature decreases. These relationships between the substitution and pressure effect in Am_4Bi_3 is very similar to that in B_4As_3. So, it may be suggested that Am_4bi_3 is a semimetal in the same way as the case of B_4As_3. The substitution effect may be different from the pressure effect though both effects finally lead to a trivalent state.