Effect of chemical disorder on Griffiths phase in weak itinerant ferromagnetic Ni92-xCuxCr8 alloy

We report magnetic and thermal properties of Cu substituted Ni92-xCuxCr8 polycrystalline alloys close to their critical concentration (x(c) similar to 18%), where ferromagnetic order disappears. From the detailed analysis of field and temperature dependent magnetization data weak itinerant ferromagnetic character has been identified for the compositions below x(c). Spin-fluctuations theory using the Ginzburg-Landau formalism further revealed the contributions of spin fluctuations, which increase near Specific heat data shows unusual low-temperature variation with an enhanced Sommerfeld coefficient and non Fermi-liquid behavior due to strong magnetic fluctuations near x(c). The magnetization data and the linear term of the specific heat follow the theoretical predictions of a ferromagnetic quantum critical point within the experimental uncertainties. The exponent of the power-law M(H) proportional to H-lambda fits to low-temperature magnetic isotherms and its variation with composition indeed suggests a possibility of quantum Griffiths phase in these alloy compositions. Finally, this study shows that the Cu substituted Ni-Cr system shows Griffiths phase at critical point even after the reduction of disorder. (C) 2022 Published by Elsevier B.V.

Automated summary

The magnetic and thermal properties of Cu-substituted Ni-Cr alloys near their critical concentration were investigated. It was found that compositions below the critical concentration exhibit weak itinerant ferromagnetic character. The magnetization and specific heat data within experimental uncertainties follow the theoretical predictions of a ferromagnetic quantum critical point. The possibility of a quantum Griffiths phase in these alloy compositions was also suggested.