• magnetocaloric effect;
  • magneto-structural transitions;
  • MnFeCoGe;
  • neutron diffraction;
  • X-ray diffraction

The crystallographic and magnetic properties of Mn0.98Fe0.02CoGe have been investigated by X-ray diffraction, dc magnetization and neutron diffraction over the temperature range 20–450 K. The temperature dependence of the phase fractions of the orthorhombic and hexagonal phases is described well by a Gaussian distribution. The Mn0.98Fe0.02CoGe sample exhibits a first-order magneto-structural transition centred at TMS ∼ 297 K of FWHM ∼37 K with a magnetic entropy change of −ΔSM = 24(1) J kg−1 K−1 for ΔB = 0–5 T. Neutron diffraction indicates a ferromagnetic orthorhombic structure below TMS with only the Mn carrying magnetic moment (3.98(6) µB) at 20 K. The sample is paramagnetic in the hexagonal phase above TMS.