Magnetic Characteristics of Lanthanide—Bismuth Compounds

The magnetic behavior of the series of lanthanide—bismuth compounds having the formula LnBi was investigated over a range of temperature extending from 4° to 300°K and at field strengths ranging from 5 to 21 kOe. Ln represents Ce, Pr, Nd, Sm, Gd, Tb, Dy, and Er. Curie—Weiss behavior was observed in the upper portion of the temperature range covered for all except SmBi. Effective moments were obtained which were in close agreement with that expected from theory for the free tripositive ions. The behavior for SmBi resembles that of elemental Sm and other Sm intermetallics and is attributed to contribution of the first excited multiplet (J=7/2). Antiferromagnetic ordering was observed for all compounds except the Pr and Sm. A Néel point for the latter probably exists but below 4°K. PrBi exhibits only Van Vleck paramagnetism to the lowest temperatures studied. This is ascribed to crystal field splitting which produces a singlet (nonmagnetic) ground state. From the limiting susceptibility an over-all splitting by the crystal field of 140 cm−1 is estimated. CeBi exhibits metamagnetism with a critical field of about 10 kOe. Its behavior as a metamagnet is atypical and is generally complex in the region where magnetic ordering occurs.