Hyperfine interactions and crystal site occupancies in RTiFe11-xCox (R=Y, Dy and Er) as seen by M?ssbauer spectroscopy

RTiFe11-xCox (R=Y, Dy, Er) systems have been studied by 57Fe M?ssbauer spectroscopy at 295 and 78 K. The composition dependencies of hyperfine interaction parameters and the relative occupancies of Fe crystal sites by Co atoms were derived from the spectra. It was found that Co atoms strongly avoid the 8i sublattice and strongly prefer the 8f and 8j sites for the three studied systems. Some anomalies in behaviour of the quadrupole interaction were observed for ErTiFe11-xCox system which can be attributed to spin reorientation transition.