Evolution of magnetic order and fluctuations in Ni-V close to the disordered ferromagnetic quantum critical point*

Muon spin rotation and magnetization data of the d-metal alloy Ni$_{1-x}$V$_{x}$ are presented at several vanadium concentrations $x$ below and above the critical $x_c \approx11\%$ where the onset of long-range ferromagnetic (FM) order is suppressed. Bulk magnetization shows signatures of a disordered quantum phase transition (QPT), most clearly in the paramagnetic regime: Above $x_c$ the temperature dependence of the magnetic susceptibility is best described by simple non-universal power laws marking a quantum Griffiths phase. But the deviations from a clean FM in the ordered phase are more subtle to recognize in the bulk magnetization and are noticed only close to $x_c$. Muon data reveal a broad field distribution in the FM regime at even small $x$ $(x \geq 4\%)$. The evolution of the magnetic cluster distribution and dynamics from the pristine FM towards the paramagnetic regime will be presented. This adds new insight in this model system at a disordered QPT.