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