Magnetic transition and spin fluctuations in the unconventional antiferromagnetic compound Yb3Pt4

TL;DR

This study investigates the magnetic transition and spin fluctuations in the unconventional antiferromagnet Yb3Pt4 using muon spin rotation and relaxation, revealing mean-field behavior, enhanced spin correlations, and properties indicative of strong electron correlations.

Contribution

The paper provides the first muon spin rotation and relaxation measurements on Yb3Pt4, elucidating its magnetic order, spin dynamics, and correlation effects in the antiferromagnetic phase.

Findings

Oscillations below T_N indicate antiferromagnetic order.

Relaxation rate shows no critical slowing down near T_N.

Enhanced spin fluctuations suggest strong electron correlations.

Abstract

Muon spin rotation and relaxation measurements have been carried out on the unconventional antiferromagnet Yb_3Pt_4. Oscillations are observed below T_N = 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 mu_B at T = 0, comparable to 0.81 mu_B from neutron diffraction. As T approaches T_N from above the dynamic relaxation rate lambda_d exhibits no critical slowing down, consistent with a mean-field transition. In the AFM phase a T-linear fit to lambda_d(T), appropriate to a Fermi liquid, yields highly enhanced values of lambda_d/T and the Korringa constant K_ mu^2 T/lambda_d, with K_ mu the estimated muon Knight shift. A strong suppression of lambda_d by applied field is observed in the AFM phase. These properties are consistent with the observed large Sommerfeld-Wilson and Kadowaki-Woods ratios in Yb_3Pt_4 (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 Yb_3Pt_4.