Applied-field-dependent magnetisation curves of the one-dimensional antiferromagnet K₂FeF₅(Mossbauer spectra)

Mossbauer spectroscopic measurements of hyperfine fields have been used to obtain information on the magnetisation curves of single crystals of K 2 FeF 5 in the presence of applied magnetic fields in the antiferromagnetic region below the Neel temperature. In zero applied field the magnetisation curve is of the expected form but with an anomalously low value of the saturation hyperfine field. With fields applied perpendicular to the magnetic easy axis the magnetisation curve is raised with respect to that in zero field but remains essentially parallel to it. For fields applied parallel to the magnetic easy axis the magnetisation curve is lowered compared with that in zero field with the effect decreasing with decreasing temperature so that the curves converge as absolute zero is approached.