APS » Journals » Phys. Rev. Lett. » Accepted Papers » Chiral properties of structure and magnetism in Mn$_{1-x}$Fe$_x$Ge compounds: When the left and the right are fighting, who wins?

Chiral properties of structure and magnetism in Mn1-xFexGe compounds: When the left and the right are fighting, who wins?

Accepted

Magnetic susceptibility measurements have shown that the compounds Mn1-xFexGe are magnetically ordered through the whole range of concentrations x = [0.0 1.0]. Small-angle neutron scattering reveals the helical nature of the spin structure with a wavevector, which changes from its maximum (|k| = 2.3 nm-1) for pure MnGe, through its minimum (|k| 0) at xc 0.75, to the value of |k| = 0.09 nm-1 for pure FeGe. The macroscopic magnetic measurements confirm the ferromagnetic nature of the compound with x = xc. The observed transformation of the helix structure to the ferromagnet at x = xc is explained by different signs of chirality for the compounds with x > xc and x < xc. We used X-ray diffraction and polarized neutron scattering to evaluate the crystallographic chirality Gc and the magnetic chirality gm of the FeGe single crystals. Similar to previous observations for FeSi-based compounds, FeGe demonstrates left-(right-) handed crystalline chirality acompained by right- (left-) handedness of the magnetic helix (Gc gm = -1). At variance, MnSi related compounds show the opposite behavior(Gc gm = 1). Since the magnetic chirality gm relates to the sign of the Dzyaloshinskii-Moriya interaction (DMI), for the same geometrical arrangement (Gc) the sign of DMI can be set by the proper choice of the transition metal.