A Mossbauer study of K₂FeCl₅.H₂O

Abstract

Mossbauer absorption spectra have been recorded for powder and single-crystal samples of the antiferromagnetic compound K2FeCl5.H2O over the temperature range 1.3-293 K and also at 4.2 K in applied magnetic fields up to 10 T. Details of the electrostatic hyperfine interaction have been deduced from the paramagnetic spectra. In the antiferromagnetic phase the spectra show the Fe spins to be aligned along the crystal a axis. An external field of 3.2 T reoriented the spins to the c axis. The observed spin reorientation phase transition was found to be very sharp, characteristic of a pure antiferromagnet. Comparisons are made with a recent study of (NH4)2FeCl5.H2O.

Single-crystal pulsed neutron diffraction structure of the antiferromagnet K2[FeCl5(H2O)] with and without applied pressure

“…An investigation of the boundaries between the paramagnetic, antiferromagnetic, and spinflop phases in the H-T phase diagram shows the bicritical point at 13.6 K and 34.1 kOe (Palacio, Paduan-Filho & Carlin, 1980). From single-crystal M6ssbauer measurements in an applied magnetic field it is deduced that the spins are aligned along the a axis in the antiferromagnetic phase and along the c axis in the spinflop phase (Karki & Hall, 1993). K2[FeCIs(H20)] is also of particular interest due to the unusual pressure dependence of its spin-flop transition field, HSF, as reported by Ortiz, Paduan-Filho & Missell (1980, 1981.…”