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

We report mu SR experiments carried out on a series of heavy-electron pseudobinary compounds U(Pt1-xPdx)(3) (x less than or equal to 0.05). For x less than or equal to 0.005 the zero-field muon depolarization is described by the Kubo-Toyabe function. However the temperature variation of the Kubo-Toyabe relaxation rate Delta(KT)(T) does not show any sign of the small-moment antiferromagnetic phase with T-N approximate to 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 less than or equal to x less than or equal to 0.05 the muon depolarization 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(Pt-0.95 Pd-0.05)3 in the paramagnetic state shows two signals for B perpendicular to c, while only one signal is observed for B parallel to c. The observation of two signals for B perpendicular to c while there is only one muon localization site (0, 0, 0), points to the presence of two spatially distinct regions of different magnetic response.