Hall coefficient of (Cr_{100- x} Al_x )₉₅Mo₅alloy system

The temperature dependence of the Hall coefficient, RH, for the (Cr100-xAlx)95Mo5 alloy system with 0 ≤ x ≤ 8.6, in the temperature range 2 K ≤ T ≤ 380 K and in a magnetic field of 4.5 T is reported. Anomalies in the form of an upturn were observed just below the Néel transition temperature, TN, for the incommensurate (I) spin density wave (SDW) alloys with x ≤ 1.3 and commensurate (C) spin density wave (SDW) alloys with x ≥ 5.3. In addition to these anomalies, alloys with x = 0, 0.5, 0.9 and 8.6 show a peculiar behaviour below TN, in which RH increases and then decreases depicting a hump on further cooling. Remarkably RH for the alloy with x = 0 shows a sign reversal of majority charge carriers from holes to electrons on cooling below 120 K. The crossover of majority charge carriers disappears by the addition of just 0.5 at.% Al into the base alloy with x = 0. The behaviour of the Hall coefficient for the alloys with x = 0, 0.5, 0.9 and 8.6, is explained in terms of the simple two band model in which both charge carriers contribute to magneto-transport properties. The relative magnetic contribution to the Hall coefficient, ΔRH(2K)/RH(2K), indicate a suppression of antiferromagnetism in the concentration range 1.7 ≤ x ≤ 4.7.