Critical exponents and universal magnetic behavior of noncentrosymmetric Fe0.6Co0.4Si

Abstract

The critical magnetic properties of a non-centrosymmetric B20 cubic helimagnet Fe0.6Co0.4Si are investigated using magnetization isotherms. It belongs to the 3D-Heisenberg universality class with short range magnetic coupling as inferred from the self-consistent critical exponents beta = 0.411 +/- 0.003, gamma = 1.325 +/- 0.062, delta = 4.223 +/- 0.004 and alpha = -0.115 +/- 0.007 in combination with exchange interaction J(r) approximate to r-(4.88). Itinerant magnetic nature of the compound is realized by the Rhodes-Wholfarth analysis. Field-induced weak first (para?helical) to second (para?field-polarized) order transition is reported to occur at low critical field due to the weak spin-orbit coupling arising from the weak Dzyaloshinksii-Moriya interactions. Our study suggests the distinct phenomenological magnetic structures for Fe-based cubic magnets (Fe1-xCoxSi and FeGe) and MnSi which cause contrasting physical properties