Quantum phase transitions and multicriticality in Ta(Fe1-xVx)2

TL;DR

This study investigates the magnetic phase diagram and quantum criticality in Ta(Fe1-xVx)2, revealing a dome-shaped SDW phase, enhanced ferromagnetic correlations, and evidence of a quantum critical point with non-Fermi liquid behavior.

Contribution

It provides a comprehensive experimental analysis of the magnetic phases and quantum critical behavior in Ta(Fe1-xVx)2, highlighting the interplay between lattice distortion and magnetic correlations.

Findings

SDW order forms a dome in the phase diagram for 0.02 < x < 0.3

Enhanced ferromagnetic correlations near x=0.02 suppress SDW transition

Evidence of a quantum critical point with non-Fermi liquid properties

Abstract

We present a comprehensive study of synthesis, structure analysis, transport and thermodynamic properties of the C14 Laves phase Ta(Fe1-xVx)2. Our measurements confirm the appearance of spin-density wave (SDW) order within a dome-like region of the x - T phase diagram with vanadium content 0.02 < x < 0.3. Our results indicate that on approaching TaFe2 from the vanadium-rich side, ferromagnetic (FM) correlations increase faster than the antiferromagnetic (AFM) ones. This results in an exchange-enhanced susceptibility and in the suppression of the SDW transition temperature for x < 0.13 forming the dome-like shape of the phase diagram. This effect is strictly related to a significant lattice distortion of the crystal structure manifested in the c/a ratio. At x = 0.02 both FM and AFM energy scales have similar strength and the system remains paramagnetic down to 2 K with an extremely large Stoner enhancement factor of about 400. Here, spin fluctuations dominate the temperature dependence of the resistivity \rho ~ T ^ 3/2 and of the specific heat C/T ~ - log(T) which deviate from their conventional Fermi liquid forms, inferring the presence of a quantum critical point of dual nature.