| Ni2MnGa is a Heusler alloy that exhibits a first order martensitic phase transition near 200 K upon cooling. Recent study showed that when Mn was partially replaced with Cr in Ni2Mn1-xCr xGa, the martensitic transformation temperature increased with increasing Cr concentration. At the same time, a sharp drop in electrical resistivity was observed in the system, and the magnitude of the drop increased with increasing Cr content. In an attempt to better understand these observations, in this thesis a series of Heusler alloys that include Ni2-xCrxMnGa, Ni1.75Cr0.25Mn0.75Co0.25Ga, Ni 1.9Cr0.1Mn0.75Co0.25Ga, and Ni 2.15Cr0.1MnGa have been investigated. The samples were fabricated by conventional vacuum arc melting technique in argon atmosphere. The characterization of the samples were performed by x-ray diffraction, dc magnetization, differential scanning calorimetry, and electrical resistivity measurements. The experimental results revealed interesting properties of the alloys that include existence of multiple magnetic and structural phases, coupled and decoupled phase transitions, large change in electrical resistivity in the vicinity of the martensitic phase transformation, and large magnetocaloric effects in selected compounds. The experimental results have been discussed in detail considering the intrinsic properties of the materials. |
