A Mossbauer investigation of orthorhombic phase YbMnO3

Yb-170- and Fe-57-Mossbauer spectra are reported for orthorhombic phase manganites YbMnO3 and Yb((Fe0.005Mn0.995)-Fe-57)O-3, respectively. Point charge model estimates of the electric field gradient agree well with experimental Fe-57-Mossbauer 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 Yb-170-Mossbauer 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 T-Yb a parts per thousand 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.