MAGNETIC-PROPERTIES OF SMN

Specific heat results for SmN give clear evidence of magnetic order at 18.2 K. Susceptibility results are less convincing, but indicate an ordering temperature in the range 13-15 K. In neutron diffraction experiments, we have found no evidence of magnetic order at temperatures above 1.6 K. By combining these apparently conflicting results with observations of the low-temperature induced form factor and of the inelastic neutron cross-section, we have been able to deduce values for the crystal-field and exchange parameters which allow a consistent interpretation of all the experimental results. We find that A4〈r4〉 = (251 ± 20) K, A6〈r6〉 = (20 ± 13) K, and the exchange interaction is ferromagnetic. For these cryst field parameters the orbital and spin contributions to the ground-state moment almost cancel exactly, giving a nearly zero ground state moment and a very unusual magnetic form factor. The strong temperature dependence of the induced form factor, expected for Sm3+ ions, has been confirmed. © 1979.