Magnetic order and spin dynamics in the proximity of a ferromagnetic quantum critical point: A {\mu}SR study of YbNi4P2

TL;DR

This study investigates the magnetic order and spin dynamics near a ferromagnetic quantum critical point in YbNi4P2 using muon-spin relaxation, revealing static magnetic order with reduced moments and critical spin fluctuations.

Contribution

It provides the first muon-spin relaxation analysis of YbNi4P2, demonstrating static magnetic order and critical spin dynamics near the quantum critical point.

Findings

Static magnetic order with reduced Yb3+ moments below 140 mK.

Quasihomogeneous spin fluctuations above TC.

Power-law behavior indicating critical spin dynamics.

Abstract

The local 4f-electronic spin dynamics and magnetic order in YbNi4P2 were studied by means of muon-spin relaxation measurements. Zero-field muon-spin relaxation proves static magnetic order with a strongly reduced ordered Yb3+ moment of (2.5-4.6) \times 10-2{\mu}B, below TC = 140 mK. Above TC, the muon-spin polarization P(t,B) is dominated by quasihomogeneous spin fluctuations and exhibits a time-field scaling relation P(t,B) = P(t/B{\gamma}), indicating cooperative critical spin dynamics in the system. At T = 190 mK, slightly above TC, {\gamma} = 0.81(5), suggesting time-scale invariant power-law behavior for the dynamic electronic spin-spin autocorrelation function.