Quantum Critical Behavior in the Asymptotic Limit of High Disorder: Entropy Stabilized NiCoCr0.8 Alloys

TL;DR

This study investigates quantum critical behavior in highly disordered NiCoCr0.8 alloys, demonstrating agreement with BKV theory and establishing entropy stabilized alloys as effective platforms for quantum critical research.

Contribution

It provides experimental verification of quantum critical exponents in metallic alloys and links high disorder to quantum critical phenomena, confirming theoretical predictions.

Findings

Critical exponents match BKV theory predictions

Magnetization data scales without adjustable parameters

Divergence of magnetic Gruneisen parameter observed

Abstract

The behavior of matter near a quantum critical point (QCP) is one of the most exciting and challenging areas of physics research. Emergent phenomena such as high-temperature superconductivity are linked to the proximity to a QCP. Although significant progress has been made in understanding quantum critical behavior in some low dimensional magnetic insulators, the situation in metallic systems is much less clear. Here we demonstrate that NiCoCrx single crystal alloys are remarkable model systems for investigating QCP physics in a metallic environment. For NiCoCrx alloys with x = 0.8, the critical exponents associated with a ferromagnetic quantum critical point (FQCP) are experimentally determined from low temperature magnetization and heat capacity measurements. For the first time, all of the five critical exponents ( gamma-subT =1/2 , beta-subT = 1, delta = 3/2, nuz-subm = 2, alpha-bar-subT = 0) are in remarkable agreement with predictions of Belitz-Kirkpatrick-Vojta (BKV) theory in the asymptotic limit of high disorder. Using these critical exponents, excellent scaling of the magnetization data is demonstrated with no adjustable parameters. We also find a divergence of the magnetic Gruneisen parameter, consistent with a FQCP. This work therefore demonstrates that entropy stabilized concentrated solid solutions represent a unique platform to study quantum critical behavior in a highly tunable class of materials.