Xavier Bohigas Janoher

Magnetic susceptibility of sodium rare-rarth fluorites Na[sub 0.5 -- x]R[sub 0.5 + x]F[sub 2 + 2x] (R [equals sign] Dy, Ho, Er, Tm, Yb) and some ordered phases

Magnetic properties of the nonstoichiometric phases with the fluorite-type “defect” structure Na0.4R0.6F2.2 (R = Ho, Er, Tm, Yb) and Na0.35Dy0.65F2.3 have been studied as well as some ordered phases with different distortions of the initial fluorite lattice (NaHo2F7, Na7Tm13F46, NaYb2F7, and Na7Yb13F46) and Na1.5Dy1.5F6 with the gagarinite-type structure (NaCaYF6). Magnetic susceptibility χ was measured with the aid of the Faraday balance in the temperature range from 20 to 300 K. The crystals with R= Dy, Ho, Er, Tm are paramagnetic; their temperature dependence χ is described by the Curie-Weiss law. It is shown that in the temperature range studied, magnetic susceptibility does not depend on the degree of order of Dy, Ho, Er, and Tm ions in the structure. Below 80 K, the temperature dependence of magnetic susceptibility of the the Yb3+-containing phases differs from the analogous dependence χ of an ideal paramagnetic crystal, which is assumed to be caused by the interaction of the crystalline field with Yb3+ ions.