Crystal and Magnetic Structures of NaMnF4

Abstract

An X-ray single crystal structure determination (monoclinic, space group P21/c, a = 573.6(2), b= 489.2(1), e = 574.8(2) pm,β = 108.07(2), Z = 2; w R = 0.038 for 380 reflections) shows that NaMnF4 crystallizes in the same layered structure type as LiMnF4. In the quadratic layers the Mn-F-Mn bridges are strongly asymmetric, due to the Jahn-Teller effect, leading to an antiferrodistortive order of elongated octahedra. The bridging angle is 138.4. The Na +ions are 6-coordinated as well. The common structural arrangements of both [MnF6] and [NaF6] octahedra shows topological relation to the rutile structure. In the magnetic measurements performed on powder samples NaMnF4 behaves as an antiferromagnet with a weak ferromagnetic component below 13 K. By neutron diffraction on powder (4–70 K) a magnetic cell doubled along the a-axis is found and below a Neel temperature of TN = 13 K the magnetic structure shows colinear antiferromagnetic arrangement of the spins pointing slightly (16°) out of the layer plane. The resulting magnetic moment is 3.52 μB. © 1991, Walter de Gruyter. All rights reserved.