Magnetic moment of cu-modified Ni₂MnGa magnetic shape memory alloys

The magnetization measurements at 5 K were carried out for Ni₂Mn_{1 −x}Cu_xGa (0 ≤ x ≤ 0.40) and Ni₂MnGa_1−yCuy (0 ≤ y ≤ 0.25) alloys. All of the magnetization curves are characteristic of ferromagnetism or ferrimagnetism. By using Arrott plot analysis the spontaneous magnetization of all samples was determined from the magnetization curves. The magnetic moment per formula unit, μ_s, at 5 K was estimated from the spontaneous magnetization. For Ni₂Mn_1−xCuxGa (0 ≤ x ≤ 0.40) alloys μ_s at 5 K decreases linearly with increasing x. On the other hand, the μ_s at 5 K for Ni₂MnGa_1−yCuy (0 ≤ y ≤ 0.25) alloys decreases more steeply with increasing x compared to the μ_s for Ni₂Mn_1−xCuxGa (0 ≤ x ≤ 0.40) alloys. On the basis of the experimental results, the site-occupation configurations of Ni₂Mn_1−xCuxGa (0 ≤ x ≤ 0.40) and Ni₂MnGa_1−yCuy (0 ≤ y ≤ 0.25) alloys are proposed.