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

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

Structural and magnetic properties of heusler alloys Pd2MnZ (Z=Ga, Ge, As): AB INITIO study

In this work, we report results of ab initio and Monte Carlo investigations of structural and magnetic properties in a series of Heusler compositions Pd2MnZ (Z = Ga, Ge, As). It was found that for Pd2MnGa and Pd2MnAs, the stable martensitic state is realized on the contrast with Pd2MnGe. The equilibrium lattice parameters for the series of Pd2MnZ (Z = Ga, Ge, As) compounds increase with increasing the number of valence electrons per atom (e/a ratio). Having calculated total magnetic moments and magnetic exchange parameters from ab initio methods, the Curie temperature for Pd2Mn-based alloys has been estimated in the framework of Monte Carlo simulations of Heisenberg model

Investigation of structural and magnetic properties of Fe-Rh-(Z) (Z = Co, Pt) alloys by first principles method

In this work, we present theoretical investigations of the structural and magnetic properties Fe (Rh, Co) and Fe (Rh, Pt) alloys using the density functional theory. The energy calculations were performed for the 16-atom supercell (Fe8Rh8-xZx) with different initial spin configurations. It is shown that a small variation of Pt or Co content leads to change the type of magnetic ordering. It is shown that the ferromagnetic configuration of Fe8Rh8-xCox (x=2, 3) is more energetically favorable as compared with other configurations in austenite. The antiferromagnetic configuration is more energetically favorable for Fe8Rh7Co1 alloy. For the Fe8Rh8-xPtx system, the checkerboard-like antiferromagnetic configuration was found to be more energetically favorable. Besides, the addition of Pt into Fe-Rh system slightly changes the optimized lattice parameter and stimulates the martensitic phase transformation

First Principles and Monte Carlo Calculations of Structural and Magnetic Properties of FexNi2-xMn1+yAl1-y Heusler Alloys

The composition dependences of crystal lattice parameters, bulk moduli, magnetic moments, magnetic exchange parameters, and Curie temperatures in FexNi2-xMn1+yAl1-y (0.2 ≤ x ≤ 1.8; 0.0 ≤ y ≤ 0.6) Heusler alloys are investigated with the help of first principles and Monte Carlo calculations. It is shown that equilibrium lattice parameters and MnY-MnZ magnetic exchange interactions increase with increasing Fe content (x). A crossover from ferromagnetic to antiferromagnetic interaction between nearest neighbors MnY and MnZ atoms was observed in compositions with x ≥ 1.4 and 0.2 ≤ y ≤ 0.6. Such magnetic competitive behavior points to a complex magnetic structure in FexNi2-xMn1+yAl1-y. Calculated values of lattice parameters, magnetic moments, and Curie temperatures are in a good agreement with other theoretical results and available experimental data

Ternary phase diagram of Ni-Mn-Ga: insights from ab initio calculations

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