Magnetic properties of rare-earth fluorides with potassium yttrium fluoride structure.

摘要

Magnetic properties of compounds possessing the cubic KY3F 10 structure were investigated for the rare earth ions (Yb, Tm, Er, Ho, Dy, Tb, Gd, and Sm) in the Yttrium crystal sites. The compounds have a novel magnetic ion structure containing three independent magnetic sites, with each site having g∥ oriented along a different x, y, or z crystallographic axis. Magnetic susceptibility measurements taken over the temperature range of 300 K to 8 mK showed ordering in all compounds except KHo3F10 and RbSm3F 10. The large values of the susceptibility at the lowest temperatures indicate that KYb3F10, KDy3F10 and KEr3F10 most likely order in a magnetically polarized state, while the other compounds order antiferromagnetically. The dipolar and exchange interactions both appear to be significant in the ordering behavior, and are of the same order of magnitude. Specific heat measurements made on RbGd3F10 lead to a value for the isotropic exchange interaction constant of Jex/KB = -0.023 +/- 0.003 K, in good agreement with that determined from the susceptibility result (Jex/K B = -0.020 +/- 0.002 K). Magnetic energy calculations for the dipolar and exchange interactions for RbGd3F10 showed an antiferromagnetic ground state, consistent with the experimental results, possessing a dipolar energy of Edip/ KB = -0.65 K and an exchange energy of Eex/KB = -1.05 +/- 0.18 K. The nuclear hyperfine interaction had a profound influence on the susceptibility of KHo3F10 which rose sharply below a half Kelvin, but never ordered magnetically.