The magnetization measurements at 5 K were carried out for Ni 2Mn 1 ？ xCu xGa (0 ≤ x ≤ 0.40) and Ni 2MnGa 1 ？ yCu y (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 Ni 2Mn 1 ？ xCu xGa (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 Ni 2MnGa 1 ？ yCu y (0 ≤ y ≤ 0.25) alloys decreases more steeply with increasing x compared to the μ s for Ni 2Mn 1 ？ xCu xGa (0 ≤ x ≤ 0.40) alloys. On the basis of the experimental results, the site-occupation configurations of Ni 2Mn 1 ？ xCu xGa (0 ≤ x ≤ 0.40) and Ni 2MnGa 1 ？ yCu y (0 ≤ y ≤ 0.25) alloys are proposed.
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