On the Nature of Defects in Mn1 –xFexGe Compounds Synthesized under High Pressure

The mesostructure of Mn1 – xFex Ge transition-metal monogermanides is studied by small-angle neutron scattering (SANS) and ultra-SANS in a wide concentration range of x = 0.0–1.0.It is shown that the main contribution to the scattering intensity for all concentrations x is made by scattering at crystallites with sharp boundaries and sizes of 1–10 μm, which is described by the squared Lorentzian function. An additional contribution to the scattering intensity as a result of scattering at an ensemble of defects is found as well, which is characteristic of manganese-rich samples. This contribution is well fitted by the power function Q–n with the exponent n = 3. The complementary scattering typical of iron-rich samples is described by an exponential function and also seems to be a part of scattering at sharp-boundary crystallites

Spin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to TC ≈ 278.7 K by small-angle neutron scattering. The method we have used is based on [Grigoriev et al., Phys. Rev. B 92, 220415(R) (2015)] and was extended here for the application in polycrystalline samples. We confirm the validity of the anisotropic spin-wave dispersion for FeGe caused by the Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness A for the FeGe helimagnet decreases with a temperature as A(T ) = 194[1 − 0.7(T/TC)4.2] meV °A2. The finite value of the spin-wave stiffness A = 58 meV °A2 at TC classifies the order-disorder phase transition in FeGe as being the first-order one

Split of the magnetic and crystallographic states in Fe1−x_{1-x}Rhx_{x}Ge

We report on a comprehensive experimental and theoretical study of Fe$_{1-x}$Rh$_{x}$Ge compounds, within the entire concentration range $x \in \left[0.0 - 1.0\right]$, using X-Ray diffraction, small-angle neutron scattering, magnetometry and theoretical calculations. While FeGe and RhGe are single phase helimagnet and unconventional superconductor, respectively, an internal splitting of the crystallographic and magnetic states is found for intermediate compositions $x \in \left[0.2 - 0.9\right]$. A theoretical analysis of the stability of the two detected phases, together with the experimental data, indicate that this splitting preserves a common space group and occurs within single crystallites. Despite their apparent similarity, these two phases however display different magnetic structures, with distinct ferro- and helimagnetic character

Spin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to T-C approximate to 278.7 K by small-angle neutron scattering. The method we have used is based on [Grigoriev et al., Phys. Rev. B 92, 220415(R) (2015)] and was extended here for the application in polycrystalline samples. We confirm the validity of the anisotropic spin-wave dispersion for FeGe caused by the Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness A for the FeGe helimagnet decreases with a temperature as A(T) = 194[1 - 0.7(T/TC) 4.2] meV angstrom(2). The finite value of the spin-wave stiffness A = 58 meV angstrom(2) at TC classifies the order-disorder phase transition in FeGe as being the first-order one