^31P NMR investigations on the ferromagnetic quantum critical system YbNi_4P_2

TL;DR

This study uses ^31P NMR to investigate the ferromagnetic quantum critical behavior of the heavy-fermion system YbNi4P2 across wide temperature and field ranges, revealing strong ferromagnetic correlations and specific fluctuation dynamics.

Contribution

It provides detailed NMR insights into the static and dynamic magnetic properties of YbNi4P2 near quantum criticality, highlighting the presence of ferromagnetic correlations and their temperature dependence.

Findings

Korringa law holds over wide temperature and field ranges.

Strong ferromagnetic correlations evidenced by Korringa product.

Temperature dependence of relaxation rate follows T^{-3/4} over two decades.

Abstract

We studied the new heavy-fermion system YbNi$_{4}$P$_{2}$, which presents strong ferromagnetic correlations, using the local $^{31}$P NMR probe over a wide field (0.2-8.6 \textsf{T}) and temperature (1.8-200 K) range. $^{31}$P NMR Knight shift provides the static spin susceptibility which tracks the bulk susceptibility whereas the spin-lattice relaxation rate $^{31}(1/T_{1}$) provide information about the fluctuations of the Yb 4f moment. The Korringa law is valid over a wide range in temperature and field. The Korringa product $^{31}(1/T_{1}TK^{2}$S$_{0}$) $\ll$ 1 gives evidence for the presence of strong ferromagnetic correlations. Over two decades in temperature a $^{31}(1/T_{1}T) \sim T^{-3/4}$ behaviour was found.