Quantum Griffiths phase inside the ferromagnetic phase of Ni$_{1-x}$V$_x$

TL;DR

This study provides evidence for a quantum Griffiths phase within the ferromagnetic region of Ni$_{1-x}$V$_x$, characterized by anomalous power-law magnetization and inhomogeneous magnetic order near the quantum critical point.

Contribution

It reveals the existence of a quantum Griffiths phase inside the ferromagnetic phase of Ni$_{1-x}$V$_x$, combining bulk and local probes to uncover inhomogeneous magnetic behavior.

Findings

Power-law magnetization with nonuniversal, x-dependent exponents

Inhomogeneous magnetic order observed via muon spin rotation

Presence of dynamic magnetic clusters indicating a Griffiths phase

Abstract

We study by means of bulk and local probes the d-metal alloy Ni$_{1-x}$V$_x$ close to the quantum critical concentration, $x_c \approx 11.6\%$, where the ferromagnetic transition temperature vanishes. The magnetization-field curve in the ferromagnetic phase takes an anomalous power-law form with a nonuniversal exponent that is strongly $x$-dependent and mirrors the behavior in the paramagnetic phase. Muon spin rotation experiments demonstrate inhomogeneous magnetic order and indicate the presence of dynamic fluctuating magnetic clusters. These results provide strong evidence for a quantum Griffiths phase on the ferromagnetic side of the quantum phase transition.