Magnetism in heavy-fermion U(Pt,Pd)3 studied by mSR

TL;DR

This study uses muon spin rotation experiments to investigate the magnetic properties of heavy-fermion U(Pt,Pd)3 compounds, revealing fluctuating small moments and spatially distinct magnetic regions, challenging previous neutron diffraction findings.

Contribution

It provides new insights into the magnetic behavior of U(Pt,Pd)3, especially the fluctuating nature of small moments and the coexistence of different magnetic responses in the material.

Findings

No evidence of static small-moment antiferromagnetism at low Pd doping.

Detection of two magnetic regions with different responses in the paramagnetic state.

Observation of fluctuating moments consistent with NMR data.

Abstract

We report mSR experiments carried out on a series of heavy-electron pseudobinary compounds U(Pt1-xPdx)3 (x<=0.05). For x<=0.005 the zero-field muon depolarisation is described by the Kubo-Toyabe function. However the temperature variation of the Kubo-Toyabe relaxation rate does not show any sign of the small-moment antiferromagnetic phase with TN~6 K (signalled by neutron diffraction), in contrast to previous reports. The failure to detect the small ordered moment suggests it has a fluctuating (> 10 MHz) nature, which is consistent with the interpretation of NMR data. For 0.01<=x<=0.05 the muon depolarisation in the ordered state is described by two terms of equal amplitude: an exponentially damped spontaneous oscillation and a Lorentzian Kubo-Toyabe function. These terms are associated with antiferromagnetic order with substantial moments. The Knight-shift measured in a magnetic field of 0.6 T on single-crystalline U(Pt0.95Pd0.05)3 in the paramagnetic state shows two signals for B perpendicular to c, while only one signal is observed for B||c. The observation of two signals for B perpendicular to c, while there is only one muon localisation site (0,0,0), points to the presence of two spatially distinct regions of different magnetic response.