First-principles Calculations On Magnetic Anisotropy Energy Of Ni₂FeGa And Metamagnetic Transition Of Nicomnz?Z=In,Sn,Sb? Alloys

Ferromagnetic shape memory alloys(FSMAs)are novel smart materials which exhibit magnetic field induced strains of up to 10%and accompany with physical effects such as magnetoresistance and magnetocaloric effect.These alloys are of great potential for technological applications in actuators,sensors and magnetic refrigeration and have become research highlights in condense matter physics and material science.In the present work,a series of first-principles calculations have been performed within the framework of the Density Functional Theory(DFT)to study the structural,elastic,magnetic anisotropy,and metamagnetic properties of Ni-Fe-Ga and Ni-Mn-(In,Sn,Sb)alloys.We compared calculations results with available experimental and other theoretical results and discussed the role of first-principles calculations in search of new FSMAs.Firstly,the structural,elastic,magnetoelastic and phonon properties of Ni2FeGa have been investigated by first-principles calculations.The calculated elastic constant,isotropic elastic moduli and Debye temperatures of Ni2FeGa are consistent with experimental or other theoretic work,and the elastic constant and magnetoelastic coefficient can be used in further phase-field simulation.The magnetic anisotropy energy behaviors of N12X(X=Mn,Fe,Co)Ga alloys were analyzed with electronic density of states and orbital moment.By comparing first-principles estimated values of magnetic and twinning stresses of N12MnGa and Ni2FeGa,we confirmed the condition that determines whether large magnetic field-induced strains in FSMAs could be obtained or not.This information can provide theoretical guidance in searching new types of FSMAs with large magnetic field induced strain.Secondly,we employed the density functional theory to investigate the structural,magnetic properties and metamagnetic transition on Mn and Co doped?Ni2MnZ(Z=In,Sn,Sb)Heusler alloys.The calculated formation energy indicates that excess Mn and Co prefer to occupy Z and Ni sites,respectively.The energy difference between austenite and martensite phases exhibits a monotonic increase with Mn doping,and a decrease with Co doping,which are consistent with the trend of experimental martensitic transformation temperature.Bond analysis of martensite phase reveals that the strength of Mn-Sb bond is stronger than that of Mn-In and Mn-Sn and it explains larger driving magnetic field in NiMnSb than NiMnZ(Z=In,Sn)is needed for metamagnetic phase transformation.In addition,we predict NiCoMnZ(Z=Sn,Sb)alloys require a smaller compressive epitaxial strain for metamagnetic transition than NiCoMnIn alloys.The lattice vibration,electric and magnetic contribution to entropy change of reverse martensitic phase transition of Ni50Mn37.5In12.5 are estimated by Debye model,electronic density of states and Brag-Williams model.Lastly,first-principles calculations were employed to investigate structural,elastic constant,electronic,and lattice dynamics of B2 ferromagnetic and antiferromagnetic FeRh phases.At finite temperatures,the values of vibrational(from both Debye model and phonon dispersion)and thermal electronic contributions to the total entropy change between the two phases were calculated about-50 J/kg/K and 7.8 J/kg/K comparable to the experimental results(-33±9 J/kg/K and 8±1 J/kg/K).