First Principles Investigation of Magnetic Properties of Fe-Ni-Mn-Al Heusler Alloys

AbstractThe composition dependences of crystal lattice parameters, magnetic moments and magnetic exchange parameters in FexNi2−xMn1+y Al1−y (0.0 ≤ x ≤ 2.0; 0.0 ≤ y ≤ 0.6) Heusler alloys are investigated with the help of first principles calculations. Our simulations have shown that crystal lattice parameter is decreased with Fe content (x) increasing. Our calculations show that increase of Fe content (x) leads increasing of magnetic exchange interactions between Mn atoms at regular positions and Mn atoms at Al positions and change of interaction sign from antiferromagnetic type to ferromagnetic one for Fe content x ≥ 1.4. Competitive behavior between ferromagnetic and antiferromagnetic interactions shows that these alloys have a complex magnetic structure. Calculated data for crystal lattice parameter, magnetic moment and magnetic exchange parameters for pure compounds (x = 0.0 and x = 2.0) are in an agreement with theoretical and experimental data

Effects of magnetic and structural phase transitions on the normal and anomalous Hall effects in Ni-Mn-In-B Heusler alloys

Magnetization, electrical resistivity, magnetoresistance, and Hall resistivity of Ni50Mn35In14.25B0.75 and Ni50Mn35In14.5B0.5 Heusler alloys were studied in a temperature range T=80-400K in magnetic fields up to 20 kOe. Both alloys exhibit a martensitic transformation from a higherature ferromagnetic austenite phase to a lowerature, low-magnetization martensitic phase. The electrical resistivity nearly doubles as a result of the martensitic transformation, reaching 180 and 100 μ cm in the martensitic states of Ni50Mn35In14.25B0.75 and Ni50Mn35In14.5B0.5, respectively. The temperature dependence of the electrical resistivity does not corresponded with the Mooij correlation. The magnetoresistance is negative with a narrow negative peak at the martensitic transition. Normal and anomalous Hall effect coefficients were determined by fitting the field dependences of the Hall resistivity using magnetization data. The coefficients of the normal Hall effect for both compositions were found to decrease with temperature from positive values in the austenite to negative values in the martensite phase. None of the known correlations between the anomalous Hall effect coefficient and resistivity were satisfied. Significant changes in the values of the anomalous Hall coefficients during the martensitic transformation are explained by the difference in spin-up and spin-down state occupations in the martensite and austenite phases. First-principles calculations of the electronic structures confirm this explanation

First-principles and Monte Carlo studies of C-doped Ni45Co5Mn37In13 Heusler alloys

In this work, we report the study of the effect of carbon on electronic and magnetic properties of the Ni45Co5Mn37In13 alloy. Two compounds with addition of 5 at.% C for Mn and In with ferro- and ferrimagnetic spin configurations have been discussed in the framework of first-principles and Monte Carlo calculations. In order to calculate the magnetic exchange parameters, magnetic moments, and electronic density of states curves we have used the SPR-KKR package. We have shown that the addition of carbon leads to enhancement of antiferromagnetic exchange interactions between Mn atoms in martensite of both compounds. The temperature dependences of magnetizations as well as Curie temperatures of austenite and martensite have been obtained

First-principles and Monte Carlo studies of C-doped Ni

In this work, we report the study of the effect of carbon on electronic and magnetic properties of the Ni45Co5Mn37In13 alloy. Two compounds with addition of 5 at.% C for Mn and In with ferro- and ferrimagnetic spin configurations have been discussed in the framework of first-principles and Monte Carlo calculations. In order to calculate the magnetic exchange parameters, magnetic moments, and electronic density of states curves we have used the SPR-KKR package. We have shown that the addition of carbon leads to enhancement of antiferromagnetic exchange interactions between Mn atoms in martensite of both compounds. The temperature dependences of magnetizations as well as Curie temperatures of austenite and martensite have been obtained

Magnetic states of C-doped Ni

In this study, we present the results of first principles calculations of structural and magnetic equilibrium states of carbon doped Ni1.75Co0.25Mn1.5In0.5 Heusler alloy. The pseudopotential method within spin-polarized generalized gradient approximation is used. Different distributions of Mn, In and C atoms as well as different spin reference states are discussed by using a supercell approach. The ferromagnetic cubic austenite with substitution of C for Mn is found to be energetically stable. The addition of carbon has promoted the martensitic transformation from a ferromagnetic cubic structure to a ferrimagnetic tetragonal structure with c/a ratio of 1.35

Magnetic states of C-doped Ni43.75Co6.25Mn37.5In12.5 Heusler alloys

In this study, we present the results of first principles calculations of structural and magnetic equilibrium states of carbon doped Ni1.75Co0.25Mn1.5In0.5 Heusler alloy. The pseudopotential method within spin-polarized generalized gradient approximation is used. Different distributions of Mn, In and C atoms as well as different spin reference states are discussed by using a supercell approach. The ferromagnetic cubic austenite with substitution of C for Mn is found to be energetically stable. The addition of carbon has promoted the martensitic transformation from a ferromagnetic cubic structure to a ferrimagnetic tetragonal structure with c/a ratio of 1.35

Ternary phase diagram of Ni-Mn-Ga: insights from

In this work we perform a wide-range systematic study of the family off-stoichiometric Ni-Mn-Ga alloys by using the supercell approach in the framework of density functional theory. Our goal is to explore the compositional variations of the structural stability and magnetic properties of Ni-Mn-Ga compositions. As a result equilibrium lattice parameters, bulk moduli, total magnetic moments, and formation energies of a wide range of Heusler alloys have been mapped on compositional ternary diagrams