Quantum critical behaviour in the (Cr_97.8Si_2.2) _100-yMo_y alloy system

The Cr-Si system offers an ideal reference alloy as a case study to follow the evolution of the well-known first-order magnetic transition in dilute Cr-Si by doping with Mo, which is iso-electronic with Cr. This alloy system, in addition, then also offers the opportunity to search for effects of quantum criticality (QC) associated with the process of driving the Néel transition temperature (T_N) to zero. Previous investigations on the ternary (Cr_97.8Si_2.2)_100-yMo _y alloy system (0 y 9) indicated possible quantum critical behaviour at a critical concentration y_c ≈ 3.8. The present paper extends these studies to additional concentrations in the alloy series, as well as to explore key indicators of QC, such as Hall coefficient (R_H) and magnetic susceptibility (χ) measurements. Recent results indicate the possible existence of two critical points in the (Cr_97.8Si _2.2)_100-yMo_y alloy system. The first critical point at y_c1 is postulated to be related to the concentration where the first-order transition gives way to a second-order-like continuous magnetic phase transition. Behaviour normally associated with QC is observed at the second critical concentration y_c2, accompanying a transition to paramagnetism.