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.
Bibliographical noteFunding Information:
Part of the work was supported by a grant from NSF (grant number: DMR-0094241). We thank S. Kreitzman, B. Hitti and D. Arsenau (TRIUMF) for assistance during the measurements.
- Muon spin rotation
- Uranium intermetallics