μSR and low-temperature antiferromagnetism in the ordered non-Fermi-liquid compound YbRh2Si2

Muon spin relaxation experiments have been carried out at low temperatures in the non-Fermi-liquid heavy-fermion compound YbRh2Si2, to study antiferromagnetism in the vicinity of the quantum critical point T=0, H∼600 Oe. The zero-field muon relaxation rate is found to be independent of temperature down to 100 mK, but increases substantially below ∼70 mK, indicative of the onset of static magnetism. The estimated internal field at a muon stopping site is ∼2 Oe, which suggests a very small ordered moment (μord∼10-3-10-2μB)