Evolution of short-range magnetic correlations in ferromagnetic Ni-V alloys

TL;DR

This study uses small-angle neutron scattering to investigate how magnetic correlations evolve in Ni-V alloys near the quantum critical point, revealing persistent short-range correlations and magnetic inhomogeneities.

Contribution

It provides new experimental insights into magnetic inhomogeneities and short-range correlations in Ni-V alloys close to the quantum critical point using polarized SANS.

Findings

Persistent isotropic short-range magnetic correlations at low temperatures.

Magnetic clusters grow in fraction as the alloy approaches the critical concentration.

Long-range magnetic domains coexist with short-range correlations below Tc.

Abstract

We experimentally study how the magnetic correlations develop in a binary alloy close to the ferromagnetic quantum critical point with small-angle neutron scattering (SANS). Upon alloying the itinerant ferromagnet nickel with vanadium, the ferromagnetic order is continuously suppressed. The critical temperature Tc vanishes when vanadium concentrations reach the critical value of xc=0.116 indicating a quantum critical point separating the ferromagnetic and paramagnetic phases. Earlier magnetization and $\mu$SR data have indicated the presence of magnetic inhomogeneities in Ni(1-x)V(x) and, in particular, recognize the magnetic clusters close to xc, on the paramagnetic and on the ferromagnetic sides with nontrivial dynamical properties [R. Wang et al., Phys. Rev. Lett. 118, 267202 (2017)]. We present the results of SANS study with full polarization analysis of polycrystalline Ni(1-x)V(x) samples with x=0.10 and x=0.11 with low critical temperatures Tc below 50 K. For both Ni-V samples close to xc we find isotropic magnetic short-range correlations in the nanometer-scale persisting at low temperatures. They are suppressed gradually in higher magnetic fields. In addition, signatures of long-range ordered magnetic domains are present below Tc. The fraction of these magnetic clusters embedded in the ferromagnetic ordered phase grows towards xc and agrees well with the cluster fraction estimate from the magnetization and $\mu$SR data. Our SANS studies provide new insights into the nature of the inhomogeneities in a ferromagnetic alloy close to a quantum critical point.