Magnetic properties of hp13 type TFe₆Ge₆(T = Zr, Nb, Hf) alloys

We have made magnetization measurements, Mössbauer spectroscopy and neutron diffraction experiments on hexagonal hp13 type TFe⁶Ge⁶(T = Zr, Hf, Nb) alloys; the la and 6i sites are entirely occupied by T( = Zr, Hf, Nb) and Fe, respectively. The alloys exhibit a simple antiferromagnetism with the magnetic moment of about 1 μ_B/Fe atom at 295 K. The Néel temperature T_N, the paramagnetic Curie temperature θ_p and the internal field H_in are as follows: T_N =495K, θ_p=70 K and H_in= 227 K for T = Zr; T_N = 462 K, θ_p = 62 K and H_in = 198 K for T = Hf; T_N = 554 K, θ_p = 71 K and H_in = 198 K for T = Nb. This is in contrast with complicated magnetic properties of the isotypic alloys such as Fe₅Mn₂Ge₆.