μ+SR in antiferromagnetic UNi4B

Abstract Positive-muon spin rotation (μ + SR) has been carried out in a single crystal of the hexagonal antiferromagnet UNi 4 B, for which the magnetic structure has recently been resolved by Mentink et al. No spontaneous precession was observed in zero field with the μ + spin directed along the rhombohedral b -axis; instead, rapidly and slowly relaxing components (comprising 70% and 30% volume fraction, respectively) were found. On the other hand, a frequency of 5 MHz was detected when the μ + spin was directed along the c -axis. Transverse-field measurements indicate that the μ + is not stopped at a highly symmetric site. The experimental results are compared with calculations based on the magnetic structure.