Magnetic properties of Heusler compounds Co1+xCrAl (x = 0, 0.25, 0.5, 0.75, 1)

Abstract

The compounds Co1+xCrAl (x = 0, 0.25, 0.5, 0.75 and 1) have been successfully prepared using the arc melting technique. Room temperature XRD patterns confirm that all compounds have Heusler compounds like fcc structure. Magnetic properties of all as-cast compounds have been studied and it is observed that all compounds are ferromagnetic below their respective PM-FM transition temperature (Tc). For half Heusler compound CoCrAl, the Tc is around 14 K but H/M as a function of temperature (T) curves at high magnetic field follows the modified Curie-Weiss law above 200 K. CoCrAl and Co1.25CrAl compounds violate the universal nature of paramagnetism (above Tc) for low magnetic field values due to the presence of magnetic clusters within the paramagnetic matrix. For the other three compounds Co1.5CrAl, Co1.75CrAl and Co2CrAl universal nature of paramagnetism and Curie-Weiss law have been satisfied properly above Tc. Except for the full Heusler compound Co2CrAl, the value of Tc increases with increasing Co concentration because lattice parameter and distance between magnetic ions decrease with increasing Co concentration. The saturation magnetization (MS) of the compounds increases with increasing Co concentration within the compounds. The saturation magnetization (MS) does not follow the well-known Slater-Pauling rule for any compounds except for CoCrAl. M−H curves for all compounds below Tc suggest the soft magnetic nature of the compounds.