Evolution of Quantum Critical Behavior In A Concentrated Ternary Solid Solution: NiCoCr$_{x\, }$

The face centered cubic (fcc) alloy NiCoCr$_{x}$ with x near 1 is found to be close to the Cr concentration where the ferromagnetic transition temperature, T$_{c}$ goes to 0. Near this composition these alloys exhibit a resistivity linear in temperature to 2 K, a perfectly linear magnetoresistance, and an excess -TlnT contribution to the low temperature heat capacity. As the Cr concentration is decreased from 1, the Curie temperature and the saturation magnetization, M$_{0}$, both increase exponentially with x. For x $=$ 0.5, T$_{c}\approx $ 217 K, but M$_{0}$ is only 0.26 Bohr magnetons/atom, indicating highly itinerant ferromagnets for 0.5 \textless x \textless 0.8. All of the low temperature electrical, magnetic and thermodynamic properties of the alloys with compositions near x$=$1 are not typical of a Fermi liquid and suggest strong magnetic fluctuations associated with a quantum critical region. This new class of concentrated solid solution fcc alloys are ideal model systems to study the effects of chemical disorder on emergent properties near a quantum critical point. Research supported by the DOE Office of Science, Materials Science and Engineering Division, and the Energy Dissipation to Defect Evolution EFRC.