Mössbauer Study of Oriented YbCrO3 Powder

The 170Yb Mossbauer effect has been used to study the local susceptibility αij of Yb3+ ions in the orthorhombic weak ferromagnet YbCrO3 at 4.2°K. By applying an external field H⇒ to a loosely packed powder absorber, YbCrO3 crystallites were oriented so that each had its weak ferromagnetic a‐axis parallel to H⇒. Absorption spectra then yielded the direction z of the EFG principal axis: z lies in the a‐b plane at an angle of 25 ± 1° to the a‐axis. For H ≤ 6 kOe, the component of the magnetic hyperfine field parallel to z increases in magnitude linearly with H: ∣Hzhf∣ = (56 ± 12) + (40 ± 6) H, with both Hzhf and H in kOe. This linear dependence is interpreted in terms of an effective‐field model. By combining our results with published single crystal magnetization data, we estimate the off‐diagonal component αab of the Yb3+ susceptibility to be ± (15 ± 13) × 10−6μB/Oe. This value is shown to be consistent with expectations for a ground state that is predominantly a ∣ ± 7/2〉 Kramers' doublet. Results of measu...