MAGNETIC CHARACTERISTICS OF LANTHANIDE-ALUMINUM COMPOUNDS

Susceptibilities (χ) for α-Ce3Al (hexagonal) are presented for the temperature range 4 °-870 °K, and for β-Ce3Al (cubic), Pr3Al, Pr2Al and PrAl4, for the temperature range 4 °-300 °K. These data together with previously published results provide magnetic information for all known Ce-Al and Pr-Al compounds. Magnetization vs. field results are also presented for these five compounds for 4 °, 77 ° and 300 °K. Both forms of Ce3Al remain paramagnetic to the lowest measured temperatures. Pr3Al and Pr2Al are ferromagnetic and antiferromagnetic, respectively, with magnetic ordering temperatures 16 ° and 18 °K, respectively. PrAl4 behaves anomalously; it may be ferrimagnetic below 12 °K. Curie-Weiss behavior is observed for temperatures in excess of 100 °K. Effective moments deduced from the temperature dependence of susceptibility are in close agreement with g √J(J + 1), the value expected for the free tripositive ion. Deviations from Curie-Weiss behavior are noted at low temperatures, originating presumably with the crystal field interaction. The six known Pr-Al series of compounds show oscillation between ferromagnetic and antiferromagnetic coupling. This is ascribed to the varying electron concentration throughout the series. In keeping with earlier observations the coupling mode for the Pr-Al series seems essentially unaffected by the crystal structure of the compound. © 1968.