Magneto-elastic transition and magnetic couplings: A Fe-57 Mossbauer spectroscopy study of the MnFeP1-xAsx system

A systematic study of MnFeP1-xAsx (0.20 less than or equal to x less than or equal to 0.50) solid solutions was undertaken by Fe-57 Mossbauer spectroscopy. The results confirm previous magnetization and neutron diffraction measurements. In the concentration range x greater than or equal to 0.30, iii which the compounds are ferromagnetic, large hyperfine fields agree with the Mn and Fe moment values. in contrast, smaller average fields are measured at low temperature in the antiferromagnetic state (x less than or equal to 0.26) from broadened Mossbauer spectra. The latter results are consistent both with the reduced value of the Fe moment and with the non-collinearity of the Fe and Mn moments. The magneto-elastic ferromagnetic double left right arrow antiferromagnetic transition has been clearly demonstrated for x = 0.275 and x = 0.30.