A 121Sb and151 Eu mössbauer spectroscopic investigation of EuMn2Sb2, EuZn2Sb2, YbMn2Sb2, and YbZn2Sb2

Schellenberg I, Eul M, Hermes W, Pöttgen R

Abstract

The antimonides EuT2Sb2 and YbT2Sb2 (T = Mn, Zn) were synthesized from the elements in sealed tantalum tubes and their structures were refined on the basis of single-crystal X-ray diffractometer data: CaAl2Si2 type, Pm1, a = 458.1(1), c = 767.4(2) pm, wR2 = 0.064, 188 F2 values for EuMn2Sb2, a = 452.6(2), c = 744.5(3) pm, wR2 = 0.026, 258 F2 values for YbMn2Sb2, a = 449.38(7), c = 761.5(1) pm, wR2 = 0.035, 355 F2 values for EuZn2Sb2, and a = 444.51(9), c = 742.7(1) pm, wR2 = 0.043, 336 F2 values for YbZn2Sb2, with 10 variables per refinement. The structures consist of puckered two-dimensional [T2Sb2]δ- networks, which are separated by the europium or ytterbium atoms. Each T and antimony atom has distorted tetrahedral coordination, while the europium and ytterbium atoms have six nearest antimony neighbors in distorted octahedral coordination. Temperature dependent 151Eu Mössbauer spectra show purely divalent europium for EuMn2Sb2 and EuZn2Sb2. At 4.2K both antimonides show full magnetic hyperfine field splitting with hyperfine fields of 26.5 (EuMn2Sb2) and 28.5T (EuZn2Sb2), respectively. The isomer shifts (-7 to -8mm·s-1) of the 121Sb Mössbauer spectra reflect the antimonide character. 121Sb Mössbauer spectra of EuMn2Sb2 and EuZn2Sb2 at 4.2K show transferred hyperfine field of ca. 9T. EuMn2Sb2 shows Curie-Weiss behavior above 630K with an experimental magnetic moment of 10.6μB/fu, indicative of divalent europium and divalent manganese. Ferromagnetic ordering of the manganese magnetic moments sets in at about 600K. At 128K (specific heat data) one observes a spin reorientation of the manganese magnetic moments and at 10K the europium atoms order antiferromagnetically.