A Mössbauer investigation of orthorhombic phase YbMnO3

Abstract

170Yb- and 57Fe-Mössbauer spectra are reported for orthorhombic phase manganites YbMnO3 and Yb(57Fe0.005Mn0.995)O3, respectively. Point charge model estimates of the electric field gradient agree well with experimental 57Fe-Mössbauer results in terms of both sign and magnitude of the electric quadrupole interaction strength, and the orientation of the magnetic hyperfine field is consistent with an E-type antiferromagnetic order where Mn moments are aligned along the a-axis (Pnma notation). The 170Yb-Mössbauer spectra exhibit pure quadrupole splitting down to 1.8 K, contradicting an earlier report that the Yb sub-lattice orders in it own right at TYb ≈ 4 K. Nevertheless, there is a slight increase in line broadening with decreasing temperature, probably due to the weak magnetic exchange field arising out of the ordered Mn sub-lattice. The small variation with temperature of the quadrupole interaction strength suggests that the Yb3+ electronic ground state is a well-isolated Kramers doublet.