We present a comprehensive small angle neutron scattering study of the doping dependence of the helimagnetic correlations in Mn_1-xFe_xSi. The long-range helimagnetic order in Mn_1-xFe_xSi is suppressed with increasing Fe content and disappears for x > x^* ≈ 0.11, i.e. well before x_C ≈ 0.17 where the transition temperature vanishes. For x > x^*, only finite isotropic helimagnetic correlations persist which bear similarities with the magnetic correlations found in the precursor phase of MnSi.

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... gnetic fields gradually suppress and partly align these short-ranged helimagnetic correlations along their direction through a complex magnetization process.