Magnetic Properties of B Doped Mn-Ga-C Based Alloys

Abstract

We present results on the structural and magnetic properties of the B-doped Mn60Ga20C20-xBx system with x=0, 2, 3, and 5.  The ball milling technique followed by pressing the sample components, and annealing under an ultra-high purity Ar atmosphere for 24 hours was employed. According to the XRD diffraction data, all samples can be described as single-phase compounds (i.e., the Mn3Ga cubic phase of Pm–3m space group) where impurity phases did not exceed 5 %. The compounds with x < 5 show similar physical behaviors as the parent, Mn3Ga2C2, which can generally characterized by a low temperature transition from low to high magnetization states. The high B concentration was found to completely suppress the antiferromagnetic state. The (x-TC, TM) phase diagram at 10 K has been evaluated and discussed. The direct magnetocaloric measurements result in magnetic entropy changes of  (-3) J(kgK)-1 at 5 T and ΔTAD  of about 0.8 K at 1.8 T.

Keywords: structural and magnetic transition, ball milling, magnetocaloric effects, carbon, Heusler alloys.