Magnetic scattering of light in K(NiMg)F3

Publisher Website
Google Scholar
Abstract
The dependence of magnon-pair excitations upon temperature and dilution of the magnetic ion concentration has been examined by inelastic light scattering in the antiferromagnetic compounds KNi1-cMgcF3. Ten values of c were examined, ranging from pure KNiF3, which shows a well defined low-temperature magnon pair at 746 cm-1, up to values above the percolation limit (c=0.68) for the perovskite structure. For increasing values of c between 0 and 0.5, the magnon-pair mode decreases in frequency and increases in linewidth in accordance with expectations based on earlier work in the (MnZn)F2 system. As the Ni concentration is lowered further the results indicate an increasing departure from expected behaviour. In particular, the pair mode continues to broaden but remains relatively constant in frequency. Quantitative magnetic data at higher values of c are precluded by disorder-induced first-order Raman scattering by phonons. A brief discussion of the phonon spectra is included. Detailed temperature dependence between 25K and 300K is also obtained for magnon pairs at several concentrations of magnesium.