Magnetic properties of binary alloys Ni1-xMox and Ni1-yCuy close to critical concentrations

The search for the ferromagnetic quantum critical point (FM QCP) has always been a captivating research topic in the scientific community. In pursuit of this goal, we introduced nonmagnetic transition metals to alloy with elemental nickel, and studied the magnetic properties of nickel binary alloys Ni1-xMox and Ni1-yCuy as a function of x and y up to the critical concentrations xcr and ycr at which the FM transition T_C disappears. T_C-x(y) phase diagrams were constructed via the Arrott-Noakes scaling of magnetization data. An enhanced Sommerfeld coefficient (the value of C/T as T → 0) is observed near ycr, manifesting the effect of quantum fluctuations near the quantum phase transition. It is evident that C/T diverges with -logT down to 0.1 K in the vicinity of ycr, suggests the plausible FM QCP in Ni1-yCuy. However, in the case of Ni1-xMox, although the enhancement of the Sommerfeld coefficient is also observed near xcr, the spin glass behavior is identified through the ac magnetic susceptibility measurement. This observation rules out the possibility of the existence of the FM QCP in Ni1-xMox.