Abstract
19F nuclear magnetic resonance (NMR) studies are performed on polycrystalline KCoFeF6 for temperatures in the range TN (110 K)<T400 K. The transferred hyperfine interaction parameters Kiso and Kax are determined at 294 K for the eight types of fluorine present in the unit cell. The results give an idea of the variation of the M-F bond lengths for different F- ions. The fractional spin transfer from the 3d to the 2s orbitals of the different F- ions has also been estimated. The temperature dependence of Kiso suggests the absence of the development of any short-range antiferromagnetic correlations within the magnetic ions bonded on either side of each type of F- ion, even very close to TN, whereas the temperature dependence of Kax suggests an appreciable enhancement of the anisotropic part of the hyperfine field below 160 K. Moreover, the intrinsic linewidths of the constituent lines increase appreciably below the same temperature, where the bulk susceptibility does not show such extra enhancement. This feature resembles the effect of slowing down of electron spin fluctuations on the 19F NMR linewidth. A comparison of the behaviour of the shift parameters with those found for KMnFeF6 indicates the dominance of geometrical frustration within the magnetic ions in the triangular lattice over the tendency of magnetic ordering of the ions belonging to the square lattice in the paramagnetic phase in KCoFeF6.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call