A μ SR magnetic study of UNiGe

We have carried out μ SR spectroscopy on polycrystalline UNiGe between 2 K and 100 K. The existence of two magnetic transitions at TN=51  K and T1=41.5  K is confirmed. The μ SR spectra clearly reveal that the magnetic state between 51 K and 41.5 K is an incommensurate spin structure ruling out a spin-slip structure which had been considered an alternative. Below 41.5 K the spectra are compatible with simple antiferromagnetic order. The local field for T→0 is Bμ=170  mT, a comparatively low value, indicating a rather small uranium ordered moment. When going from the commensurate to the incommensurate structures at T1 a sudden reduction in local field by 23% occurs reflecting an equal change in ordered moment. The transition at T1 is sharp, but TN extends over roughly 5 K. The antiferromagnetic spin structure exhibits persistent spin fluctuations in the limit T→0, implying the presence of some additional spin interactions which tries to suppress long-range magnetic order.