A Mössbauer spectroscopy investigation of h-YbMnO₃

Abstract

170Yb and 57Fe Mossbauer spectra are reported for hexagonal phase YbMnO3 and Yb(57FexMn1−x)O3 (x = 0.005, 0.01), respectively. The dilute concentrations of 57Fe are demonstrated to provide a reliable, non-perturbing Mossbauer spectroscopy probe of the Mn sub-lattice magnetization. Substitution of up to 1 at.% 57Fe exerts negligible influence on the Neel temperature (TN1≈88–89 K) and point charge model estimates of the electric field gradient agree well with experimental 57Fe Mossbauer results in terms of both sign and magnitude. The 170Yb Mossbauer spectrum recorded at 4.5 K provides support for strong crystal field quenching with isolated Kramers doublet ground states at both Yb sites. A 'static', five-line sub-spectrum is tentatively assigned to the 4b site, for which the slowed fluctuation of the Kramers doublet is attributed to non-zero magnetic exchange with the antiferromagnetic Mn sub-lattice. This is not the case for the 2a site whose sub-spectrum is a motionally narrowed single line. On the basis of this work, the saturation magnetization for the ordered Yb sub-lattice (TN2≤3 K) is estimated at ≈1.8 µB per formula unit, in close agreement with single-crystal magnetization data reported elsewhere.