Spin-density-wave effects in the (Cr98.4Al1.6)100−yMoy alloy system

• The magnetic phase diagram is obtained for the (Cr98.4Al1.6)100−yMoy alloy system.
• It indicates a putative quantum critical point at yc=4.5.
• Specific heat measurements support this conjecture.
• Novel triple point behaviour is indicated for the Cr1−zAlz alloy system.

The possibility of quantum critical behaviour in a spin-density-wave antiferromagnetic (Cr98.4Al1.6)100−yMoy alloy system is investigated through electrical resistivity, Seebeck coefficient and specific heat measurements. Magnetic resistivity anomalies associated with the Néel transition temperature are highly enhanced in the thermoelectric measurements, allowing for complementary methods in obtaining the Néel temperatures of these alloys. The results indicate a suppression of the Néel temperatures to below 2 K for alloy concentrations y≳4.5. This aspect is strongly reflected in the y-dependence of the residual resistivity and Sommerfeld specific heat coefficient. Both parameters depict rather sharp changes, related to spin-density-wave energy gap influences, on entering the antiferromagnetic phase when y is decreased at 2 K through yc≈4.5 on the concentration-temperature magnetic phase diagram. The behaviour of the concentration dependence of the Sommerfeld specific heat coefficient is suggestive of quantum critical behaviour in this alloy system, with a quantum critical point at y≈yc.