Research Of The New Materials And Their Electronic Structure In Mn-based Heusler Alloys

This paper mainly explores several new ferromagnetic shape memory alloys inMn-based Heusler alloys. The electronic structure, magnetic properties and martensitictransformation in these alloys have been studied by first-principles calculations. A series ofsamples were prepared by arc melting. And their crystal structure, magnetic properties andmartensitic transformation were investigated by X-ray diffraction and magneticmeasurements.A new Mn-based Heusler alloy Mn2PtIn has been investigated. The martensitictransformation in Mn2PtIn was confirmed by first-principles calculations and experimentalstudies. Compared with other Mn-based FSMAs, Mn2PtIn has a high phase transitiontemperature. A series of Mn2YIn (Y=Ni, Pd, Pt) alloys have been synthesized. Combinedwith first-principles calculations, we found that martensitic transformation is not likely tooccur in either Mn2NiIn and Mn2PdIn.The electronic structure and magnetic properties of Mn2Ni1.5In0.5have been studied.The site occupation in this alloy was determined theoretically. Martensitic transformationmay occur in Mn2Ni1.5In0.5, and a ferromagnetic-antiferromagnetic transition happensfollow it. The magnetic transition mainly comes from the change in magnetic moment ofMn in D site. A series of Mn50Ni25+xIn25-x(x=12.5,15,17.5,20,22.5) alloys have beensynthesized. The experimental results show that, martensitic transformation occurs at x=17.5,20,22.5, and the phase transition temperature is increased.The electronic structure and magnetic properties of Mn2PtZ (Z=Al, Ga, Ge, In, Sn, Sb)were investigated by theoretical calculations. It is found that, the martensitic transformationmay occur in these alloys. Compared with Mn2PtIn, phase transitions in other five alloysare more likely to happen.At last, we investigated the effect of Mn content on the magnetic properties andmartensitic transformation in Mn2-xNi1+xGa (x=0,0.25,0.5,0.75,1) alloys. Theoreticalcalculations and experimental studies confirmed the martensitic transformation in thesealloys. With the lowering of Mn content, the phase transition temperature first decreasesand then increases, the magnetic moment increases monotonically.