Magnetic transition and spin fluctuations in the unconventional antiferromagnetic compound Yb3Pt4
Abstract
Muon spin rotation and relaxation measurements have been carried out on the unconventional antiferromagnet Yb3Pt4. Oscillations are observed below TN = 2.22(1) K, consistent with the antiferromagnetic (AFM) Neel temperature observed in bulk experiments. In agreement with neutron diffraction experiments the oscillation frequency omega mu(T) follows a S = 1/2 mean-field temperature dependence, yielding a quasistatic local field 1.71(2) kOe at T = 0. A crude estimate gives an ordered moment of ~0.66 muB at T = 0, comparable to 0.81 muB from neutron diffraction. As T approaches TN from above the dynamic relaxation rate lambdad exhibits no critical slowing down, consistent with a mean-field transition. In the AFM phase a T-linear fit to lambdad(T), appropriate to a Fermi liquid, yields highly enhanced values of lambdad/T and the Korringa constant K mu2 T/lambdad, with K mu the estimated muon Knight shift. A strong suppression of lambdad by applied field is observed in the AFM phase. These properties are consistent with the observed large Sommerfeld-Wilson and Kadowaki-Woods ratios in Yb3Pt4 (although the data do not discriminate between Fermi-liquid and non-Fermi-liquid states), and suggest strong enhancement of q ~ 0 spin correlations between large-Fermi-volume band quasiparticles in the AFM phase of Yb3Pt4.