Magnetic Phase Diagram of the Ferromagnetic Shape Memory Alloys Ni2MnGa1-xCux

X-ray powder diffraction, permeability, magnetization and differential scanning calorimetry measurements were carried out on the magnetic shape memory alloys Ni2MnGa1−xCux (0 ≤ x ≤ 0.25). On the basis of the experimental results, the phase diagram in the temperature– concentration plane was determined for this alloy system. The determined phase diagram is spanned by the paramagnetic austenite phase (Para-A), paramagnetic martensite phase (Para-M), ferromagnetic austenite phase (Ferro-A), ferromagnetic martensite phase (Ferro-M) and the premartensite phase. It was found that the magnetostructural transition between the phases Para-A and Ferro-M can occur in the concentration region 0.12 < x ≤ 0.14 and that Ni2MnGa1−xCux has the characteristics of the phase diagram similar to those of the phase diagrams of Ni2+xMn1−xGa and Ni2Mn1−xCuxGa. In order to understand the phase diagram, the phenomenological free energy as a function of the martensitic distortion and magnetization was constructed and analyzed.

[1]  T. Shishido,et al.  Martensitic transition, ferromagnetic transition, and their interplay in the shape memory alloys Ni2Mn1-xCuxGa , 2010 .

[2]  Huibin Xu,et al.  Search for transformation from paramagnetic martensite to ferromagnetic austenite: NiMnGaCu alloys , 2009 .

[3]  I. Dubenko,et al.  Effect of small changes in Mn concentration on phase transition temperatures and magnetic entropy variations in Ni2Mn0.75Cu0.25Ga Heusler alloys , 2009 .

[4]  F. Albertini,et al.  Magnetocaloric Properties and Magnetic Anisotropy by Tailoring Phase Transitions in NiMnGa Alloys , 2008 .

[5]  Guangheng Wu,et al.  Experimental and theoretical investigations of the magnetocaloric effect of Ni2.15Mn0.85-xCuxGa (x= 0.05,0.07) alloys , 2008 .

[6]  Mahmud Tareq Hassan Khan,et al.  Phase transitions and corresponding magnetic entropy changes in Ni2Mn0.75Cu0.25−xCoxGa Heusler alloys , 2007 .

[7]  Mahmud Tareq Hassan Khan,et al.  Inverse magnetocaloric effect in ferromagnetic Ni50Mn37+xSb13−x Heusler alloys , 2007 .

[8]  C. Larica,et al.  La(Fe1−xCox)11.44Al1.56: A composite system for Ericsson-cycle-based magnetic refrigerators , 2006 .

[9]  Mahmud Tareq Hassan Khan,et al.  Magnetocaloric Properties of Ni2Mn1−xCuxGa , 2006 .

[10]  T. Takagi,et al.  Erratum: Phase transitions in Ni 2 + x Mn 1 − x Ga with a high Ni excess [Phys. Rev. B 72 , 224408 (2005)] , 2006 .

[11]  Carlo Paolo Sasso,et al.  Magnetostructural transition and magnetocaloric effect in Ni55Mn20Ga25 single crystals , 2005 .

[12]  L. Mañosa,et al.  Magnetocaloric and shape-memory effects in Ni-Mn-Ga ferro-magnetic alloys , 2004 .

[13]  T. Takagi,et al.  Magnetocaloric effect in Ni2+xMn1−xGa Heusler alloys , 2004 .

[14]  M. Napoletano,et al.  Composition dependence of magnetic and magnetothermal properties of Ni-Mn-Ga shape memory alloys , 2004 .

[15]  T. Takagi,et al.  Magnetocaloric effect and magnetization in a Ni–Mn–Ga Heusler alloy in the vicinity of magnetostructural transition , 2003, cond-mat/0312110.

[16]  Z. Altounian,et al.  Effect of Co content on magnetic entropy change and structure of La(Fe1−xCox)11.4Si1.6 , 2003 .

[17]  T. Takagi,et al.  Entropy change at the martensitic transformation in ferromagnetic shape memory alloys Ni2+xMn1−xGa , 2003, cond-mat/0302352.

[18]  K. Ziebeck,et al.  The crystal structure and phase transitions of the magnetic shape memory compound Ni2MnGa , 2002 .

[19]  F. Albertini,et al.  Giant entropy change at the co-occurrence of structural and magnetic transitions in the Ni Mn Ga Heusler alloy , 2002, cond-mat/0209564.

[20]  S. Fujieda,et al.  Large magnetocaloric effect in La(FexSi1−x)13 itinerant-electron metamagnetic compounds , 2002 .

[21]  F. Hu,et al.  Magnetic entropy change in Ni50.1Mn20.7Ga29.6 single crystal , 2001 .

[22]  F. Hu,et al.  Large magnetic entropy change in a Heusler alloy Ni 52.6 Mn 23.1 Ga 24.3 single crystal , 2001 .

[23]  F. Hu,et al.  Magnetic entropy change in Ni51.5Mn22.7Ga25.8 alloy , 2000 .

[24]  V. V. Kokorin,et al.  Large magnetic‐field‐induced strains in Ni2MnGa single crystals , 1996 .

[25]  T. Takagi,et al.  Structural and magnetic phase transitions in shape-memory alloys Ni 2+x Mn 1-x Ga , 1999 .