Ordered magnetic frustration: XVII. Is BaMnFeF7 frustrated? Mössbauer spectroscopy, magnetic susceptibility, and magnetic structure at 2 K

Abstract The results of a series of magnetic measurements on the fluoride BaMnFeF 7 , including magnetic susceptibility, Mossbauer spectra, and neutron powder diffraction, are presented. The compound orders antiferromagnetically below T N = 84.9(5) K and its paramagnetic Curie temperature is θ P = −217(5) K. The Mossbauer parameters are in good agreement with those of other iron(III) fluorides. The magnetic structure determined by neutron diffraction ( R mag = 0.052) shows that the spin sublattices of Mn and Fe each are ferromagnetic and mutually are coupled antiferromagnetically. The magnetic moments lie in the ( a,c ) plane, mainly oriented along the c direction. The presence of magnetic frustration in the compound depends on the sign of the 90° exchange interaction MnFMn. Whatever this sign may be, the weakness of this interaction guarantees the consistency of the magnetic structure with the known d 5 - d 5 coupling mechanisms.