Work

Magnetism of Pd1−x Nix alloys near the critical concentration for ferromagnetism

Year: 2014

Type: article

Abstract: We report results of a muon spin rotation and relaxation (μSR) study of dilute Pd 1-x Ni x alloys, with emphasis on Ni concentrations x = 0.0243 and 0.025.These are close to the critical value x cr for the onset of ferromagnetic long-range order (LRO), which is a candidate for a quantum critical point.Additional control data were taken for pure nonmagnetic Pd, and for an alloy where ferromagnetism is well established (x = 0.05).The 2.43 and 2.5 at.%Ni alloys exhibit similar μSR properties.Both samples are fully magnetic, with average zero-temperature muon local fields B loc (T =0) = 2.0 and 3.8 mT and Curie temperatures T C = 1.0 and 2.03 K for 2.43 and 2.5 at.%Ni, respectively.The temperature dependence of B loc suggests ordering of Ni spin clusters rather than isolated spins.Just above T C , the temperature where LRO vanishes, a two-phase region is found with coexisting separate volume fractions of quasistatic short-range order (SRO) and paramagnetism.The SRO fraction decreases to zero with increasing temperature a few kelvin above T C .This mixture of SRO and paramagnetism is consistent with the notion of an inhomogeneous alloy with Ni clustering.The measured values of T C extrapolate to x cr = 0.0236 ± 0.0027.The dynamic muon spin relaxation in the vicinity of T C differs for the two samples: a relaxation-rate maximum at T C is observed for x = 0.0243, reminiscent of critical slowing down, whereas for x = 0.025 no dynamic relaxation is observed within the μSR time window.The data suggest a mean-field-like transition in this alloy.

Source: Physical Review B

DOI: 10.1103/physrevb.89.064418