Capturing the interplay between lattice distortions and magnetic correlations in Nd2Ru2O7 pyrochlore with muon spin relaxation

Abstract We investigate how lattice distortions reshape the magnetic correlations and muon-spin relaxation (μSR) response of the frustrated pyrochlore Nd2Ru2O7. Because implanted muons occupy minima of the electrostatic potential, temperature-dependent modifications of the RuO6 network alter both the muon stopping-site landscape and the quasistatic internal fields sensed by the muons. To capture this magneto-structural coupling, we develop a mixed static–dynamic depolarization framework in which an ordered internal field is convoluted with an exponential random field associated with domain-wall or cluster-like magnetic textures and averaged over a Lorentzian distribution representing structural inhomogeneity, while a phenomenological exponential term describes dynamic Ru-moment fluctuations. Simulations further show that, within the strong-collision scheme, the dynamical narrowing effect depends sensitively on the degree of static disorder and can disappear completely for sufficiently broad random-field distributions. The model demonstrates that broad quasistatic disorder can strongly suppress oscillatory and Kubo–Toyabe-like features, producing relaxation spectra often attributed solely to rapid spin dynamics. Application to ZF- and LF-μSR spectra reveals anomalies near 145, 31, and 21 K associated with spatially inhomogeneous antiferromagnetic correlations and low-temperature magnetic restructuring. Although LF measurements under 3850 G show predominantly dynamic long-time relaxation, a residual short-time relaxation below t ~ 1–2 μs indicates surviving quasistatic magnetic regions consistent with cluster-like spin-glass behavior stabilized by structural disorder.