Observation of the crossover from quantum to classical critical behavior in ferromagnetic alloys of Pd 1− xNi x

Abstract

The magnetization of Pd 1− x Ni x alloys was measured and the transition temperature T c was determined by Arrott plots. The critical concentration was found to be x c=0.022. For x⪢x c , T c indicates the Fermi liquid behavior, T c∼| x− x c| 1/2. Close to x c, on the other hand, T c follows a new power-law T c ∼|x−x c | zν (zν=1.6) , where ν is the static critical exponent and z the dynamic critical exponent. The quantum critical region for Pd 1− x Ni x is found to be ( x− x c)/ x c<0.1. These results suggest the evidence of the crossover from quantum to classical critical behavior in ferromagnetic alloys of Pd 1− x Ni x . We also derive the critical exponent β ∗ in ferro-to-paramagnet quantum-phase transition (FPQPT) from the concentration scaling for the magnetization M 0 (M 0∼|x−x c | β ∗ , β ∗=0.14) in the quantum critical region. We propose a new phase diagram for the itinerant electron ferromagnet Pd 1− x Ni x .