Figure 1. Crystal structure and helical magnetic order in the β-Mn-type Co-Zn-Mn alloys.

(a,b) Schematic of β-Mn-type structure with (a) P4₁32 and (b) P4₃32 space group, dependent on its handedness (chirality). It contains two crystallographic sites, that is, 8c with the three-fold site symmetry occupied by Co atoms (indicated by blue circle) and 12d with the two-fold site symmetry occupied by both Zn and Co atoms (indicated by grey circles) in the case of Co₁₀Zn₁₀ (ref. 29). (c) Temperature dependence of the magnetization for a series of polycrystalline Co-Zn-Mn alloys measured at H=20 Oe on cooling. (d,e) Small-angle neutron scattering (SANS) images for polycrystalline samples of Co₁₀Zn₁₀ and Co₇Zn₇Mn₆ at T=317 K, H=300 Oe and T=120 K, H=250 Oe, respectively. The magnetic field direction is perpendicular to the neutron beam, which is itself into the page. (f) Composition dependence of the helical ordering temperature (filled blue circles) and helical pitch obtained by the SANS measurements (filled red squares) and LTEM observations (open red circles), respectively.