31P NMR investigations on the ferromagnetic quantum critical system YbNi4P2

We studied the heavy-fermion system YbNi${}_{4}$P${}_{2}$, which presents strong ferromagnetic correlations, using the local ${}^{31}\phantom{\rule{-0.16em}{0ex}}$P NMR probe over a wide field (0.2--8.6 T) and temperature (1.8--200 K) range. The ${}^{31}\phantom{\rule{-0.16em}{0ex}}$P NMR Knight shift provides the static spin susceptibility which tracks the bulk susceptibility whereas the spin-lattice relaxation rate ${}^{31}(1/{T}_{1}$) provides information about the fluctuations of the Yb $4f$ moment. The Korringa law is valid over a wide range of temperature and field. The Korringa product ${}^{31}(1/{T}_{1}T{K}^{2}{S}_{0})\ensuremath{\ll}1$ gives evidence for the presence of strong ferromagnetic correlations. A ${}^{31}(1/{T}_{1}T)\ensuremath{\sim}{T}^{\ensuremath{-}3/4}$ behavior was found over two decades in temperature.