Magnetic Susceptibility of Yb3+ in an Octahedral Environment

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The magnetic susceptibility of Yb3+ in Cs2NaYbCl6 was measured from 2.5 to 100°K and showed Curie–Weiss temperature dependence from 2.5 to 20°K (μeff = 2.46 μB, θ = 0.95°C) and from 45 to 100°K (μeff = 4.47 μB, θ = 70°C), with a transitional region from 20–45°K. From a comparison of the experimental results with theoretical results for a J = 7 / 2 ion in an octahedral field, the two crystalline field levels observed were identified as a Γ6 ground level, and a Γ8 level about 60 cm−1 higher. The energy separation between the Γ6 and Γ8 levels and a ratio of the crystalline field parameters − b4 / b6 derived from other measurements were employed to deduce − b4 = 4.85–4.95 and b6 ≈ 0.05 − 0.002 cm−1. From these parameters, a Γ7 level at ∼ 160 cm−1 is predicted. A covalent contribution to the Γ6 ground level is considered.