Interesting magnetic properties of Fe$_{1-x}$Co$_x$Si alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed. (FC) mode in various applied H. We observe two distinct features for H ≤ 500 Oe, namely qualitative features have also been observed for x = 0.1,0.15 and 0.45. Both these features, which disappear with H > 500Oe, have not been reported so far (to our knowledge) for these (Fe, Co)Si alloys.