Ab initio investigation of the structural and magnetic properties of Ni-Pt-Mn-Ga alloys
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Ab initio investigation of the structural and magnetic properties of Ni-Pt-Mn-Ga alloys Mikhail A. Zagrebin1,2, Vladimir V. Sokolovskiy1,3, Vasiliy D. Buchelnikov1, Peter Entel4 and Sergey V. Taskaev1 1 Chelyabinsk State University, 129 Brat’ev Kashirinykh Str., Chelyabinsk,454001, Russia 2 National Research South Ural State University, 78 Lenina prospect, Chelyabinsk, 454080, Russia 3 National University of Science and Technology “MISiS”, 4 Leninsky prospect, Moscow, 119049, Russia 4 University of Duisburg-Essen, 1 Lotharstr., Duisburg Campus, Duisburg, D-47048, Germany. ABSTRACT Structural and magnetic properties of Ni2-xPtxMnGa alloys are investigated from first principles calculations with the help of the spin-polarized relativistic Korringa-Kohn-Rostoker and Plane-Wave Self-Consistent Field methods. The atomic chemical disorder at specific site has been implemented using coherent potential approximation. Calculated equilibrium lattice parameters are in a good agreement with experimental data and other theoretical calculations. The composition dependences of the magnetic exchange couplings and the Curie temperature for cubic phase are obtained. Our calculations have shown that an increase content of Pt results to decrease of magnetic interactions between Mn atoms and to change of interaction sign from ferromagnetic type to antiferromagnetic one for composition Ni1.0Pt1.0MnGa. Calculated Curie temperatures are in an agreement with experimental data. INTRODUCTION The Heusler Ni-Mn-Ga alloys are interesting for practical applications because of the numerous unique effects such as a shape memory effect in ferromagnetic state, a magnetic shape memory effect, a giant magnetocaloric effect and magnetostriction etc. The strong magnetoelastic interaction between the magnetic and structural subsystem is one of the reason of these effects. The magnetic field-induced strain in Ni-Mn-Ga alloys reaches about of 10% [1,2]. The recent ab initio works have shown that the Pt adding in Ni–Mn–Ga alloys, a higher the magnetic field induced strain of 14% can be achieved [3,4]. In this work we presented results of ab initio investigations of structural and magnetic properties of Ni-Pt-Mn-Ga Heusler alloys. AB INITIO CALCULATION DETAILS In this study the calculations were performed within two different ab initio codes: the open Source Package for Research in Electronic Structure, Simulation, and Optimization (Quantum ESPRESSO) [5] and the spin-polarized relativistic Korringa-Kohn-Rostoker Munich (SPR-KKR) [6,7] package. The Quantum ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave).
The Quantum ESPRESSO was used to determine the optimized lattice parameter of cubic L21 phase Ni2-xPtxMnGa. Structural optimizations are performed using the Broyden-FletcherGoldfarb-Shanno algorithm [5]. Magnetic exchange parameters calculations are carried out using t
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