Interplay of quadrupolar order, Ce 4f spin dynamics and RKKY induced conductionelectron spin polarization in CeAg

Abstract

We report on measurements of the Knight shiftK and spin–latticerelaxation rate λ of positive muons (μ+) implanted in cubic CeAg, a compound which is known to possess ferromagnetic( K) and ferroquadrupolar (TQ = 15–16 K) order. The zero field (ZF) λ implies randomly and isotropically fluctuating Ce 4f moments aboveTQ which show a trend to a, perhaps critical, slowing down on approachingTQ.Below TQ the fluctuations are restricted to the now tetragonally distorted axis of CeAg. In alongitudinal field the generally isotropic fluctuations show a tendency towards freezing nearTc,not TQ. The Knight shift results reveal an anisotropic contact hyperfine coupling parameterAc, which displaysabrupt changes at Tc. ZFmeasurements below Tc reveal the presence of discrete spontaneous internal fields. The results onλ and Ac are interpreted as arising from quadrupolar effects, concerning in particular the inducedspin polarization of the conduction electron system.