MAGNETOELASTIC 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 t han or equal to 0.50) solid solutions was undertaken by Fe-57 Mossbaue r spectroscopy. The results confirm previous magnetization and neutron diffraction measurements. In the concentration range x greater than o r equal to 0.30, iii which the compounds are ferromagnetic, large hype rfine fields agree with the Mn and Fe moment values. in contrast, smal ler average fields are measured at low temperature in the antiferromag netic state (x less than or equal to 0.26) from broadened Mossbauer sp ectra. The latter results are consistent both with the reduced value o f the Fe moment and with the non-collinearity of the Fe and Mn moments . The magneto-elastic ferromagnetic double left right arrow antiferrom agnetic transition has been clearly demonstrated for x = 0.275 and x = 0.30.