19F nuclear magnetic resonance studies in the paramagnetic phase of the planar antiferromagnet CsFeF4

Abstract

19F NMR spectra of polycrystalline CsFeF4 in the paramagnetic region between 160 and 300 K reveal two distinct types of fluorine site. From the lineshift measurement together with the available magnetic susceptibility data, the value for the transferred hyperfine coupling between the fluorine nuclear spin and the neighbouring iron electron spin has been derived. The values of the hyperfine tensor components indicate the almost isotropic nature of the Fe-F bond. An essentially different behaviour of the linewidth as a function of the temperature of fluorine atoms (FI) bonded with one iron neighbour and fluorine atoms (FII) bonded with two iron neighbours is observed. This is similar to the 19F NMR results in the paramagnetic phase of a well known two-dimensional antiferromagnet such as K2MnF4.