A Guide to Monte Carlo Simulations in Statistical Physics: Some necessary background

This text is a modern treatment of the theory of solids. The core of the book deals with the physics of electron and phonon states in crystals and how they determine the structure and properties of the solid. The discussion uses density functional theory as a starting point and covers electronic and optical phenomena, magnetism and superconductivity. There is also an extensive treatment of defects in solids, including point defects, dislocations, surfaces and interfaces. A number of modern topics where the theory of solids applies are also explored, including quasicrystals, amorphous solids, polymers, metal and semiconductor clusters, carbon nanotubes and biological macromolecules. Numerous examples are presented in detail and each chapter is accompanied by problems and suggested further readings. An extensive set of appendices provides all the necessary background for deriving all the results discussed in the main body of the text.

Atomic and Electronic Structure of Solids

Half-metallic ferromagnetic (HMF) materials show high spin polarization and are therefore interesting to researchers due to their possible applications in spintronic devices. In these materials, while one spin sub band has a finite density of states at the Fermi level, the other sub band has a gap. Because of their high Curie temperature and tunable electronic structure, HMF Heusler alloys have a special importance among the HMF materials. Full Heusler alloys with the stoichiometric composition X2YZ (where X and Y are the transition metals and Z is a sp element) have the cubic structure with four interpenetrating fcc sublattices. When each of these four fcc sublattices is occupied by different atoms, a quaternary Heusler structure with different structural symmetry is obtained. Recently, these equiatomic quaternary Heusler alloys (EQHAs) with 1:1:1:1 stoichiometry have attracted a lot of attention due to their superior magnetic and transport properties.

Equiatomic quaternary Heusler alloys: a material perspective for spintronic applications

We report the structural and physical properties of epitaxial Bi2FeCrO6 thin films on epitaxial SrRuO3 grown on (100)-oriented SrTiO3 substrates by pulsed laser ablation. The 300 nm thick films exhibit both ferroelectricity and magnetism at room temperature with a maximum dielectric polarization of 2.8 microC/cm2 at Emax = 82 kV/cm and a saturated magnetization of 20 emu/cc (corresponding to ~ 0.26 Bohr magneton per rhombohedral unit cell), with coercive fields below 100 Oe. Our results confirm the predictions made using ab-initio calculations about the existence of multiferroic properties in Bi2FeCrO6.

Growth, Structure and Properties of Epitaxial Thin Films of First Principles Predicted Multiferroic Bi2FeCrO6

Computer simulations within the framework of density functional theory are performed to study the electronic, dynamic, elastic, magnetic, and thermoelectric properties of a newly synthesized FeRhCrGe alloy and a theoretically predicted FeRhCrSi alloy. From the electronic structure simulations, both FeRhCrZ (Z = Si and Ge) alloys at their equilibrium lattice constants exhibit half-metallic ferromagnetism, which is established from the total magnetic moment of 3.00 μB, and that the spin moment of FeRhCrGe is close to the experimental value (2.90 μB). Their strength and stability with respect to external pressures are determined by simulated elastic constants. The Debye temperatures of FeRhCrSi and FeRhCrGe alloys are predicted to be 438 K and 640 K, respectively, based on elastic and thermal studies. The large power factors (PFs) of the two investigated alloys are in contour with those of the previously reported Heusler compounds. Besides, the conservative estimate of relaxation time speculated from the experimental conductivity value is 0.5 × 10−15 s. The room temperature PF values of FeRhCrSi and FeRhCrGe compounds are 2.3 μW/cm K2 and 0.83 μW/m K2, respectively. Present investigations certainly allow the narrow bandgap, spin polarization, and high PF values to be looked upon for suitable applications in thermoelectrics and spintronics.

Thermoelectric properties, phonon, and mechanical stability of new half-metallic quaternary Heusler alloys: FeRhCrZ (Z = Si and Ge)

In this manuscript, we investigate the physical properties such as the magnetic and the electronic properties of the Co-based equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge). These investigations have been performed by employing the Quantum Espresso code in the framework of density functional theory (DFT). The generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) is used for all these calculations. The band structures, and density of states calculations, show that all these materials CoYCrZ (Z = Si and Ge) exhibit a half-metallic (HM) behavior only for the structure type II. Moreover, this structure type II is found to be the most stable configuration for all these alloys. On the other hand, it has been found that the Slater–Pauling is well described for the compound CoYCrGe, only for the configuration type II. In particular, the equiatomic quaternary Heusler alloys CoYCrSi and CoYCrGe are found to be half-metallic for the structure type II. This is due to the fact that they have 100% spin polarization SP. Also, the existence of complete SP in the studied alloys is the reason for which these materials are useful for spintronic device applications.

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

Structural, electronic, magnetic properties and critical behavior of the equiatomic quaternary Heusler alloy CoFeTiSn

In this manuscript, we study the structural, electronic, and magnetic properties of the equiatomic quaternary Heusler alloy ZnCdRhMn in the framework of the first-principle calculations and Monte Carlo simulations. In fact, we have investigated the structural, the magnetic, and the electronic properties of the Zn-based equiatomic quaternary Heusler alloy ZnCdRhMn using the ab initio method in the bases on the GGA approximation. On the other hand, the critical behavior of the equiatomic quaternary Heusler alloy ZnCdRhMn has been outlined by the Monte Carlo simulations. For this end, we apply the Metropolis algorithm. The objective of this work is to improve the competition between the austenitic and martensitic phases on the existence of magnetic and electronic properties of this alloy. The half-metallic behavior is only improved for the austenitic structure and 100% of spin polarization has been found. Moreover, a high curie temperature is found for this alloy for the austenitic phase. We can conclude that the austenitic structure of this alloy is useful for the spintronic device applications.

Characterization of the Equiatomic Quaternary Heusler Alloy ZnCdRhMn: Structural, Electronic, and Magnetic Properties

The double perovskite Sr2CrIrO6 has very important characteristics for spintronic applications. It is a ferrimagnetic material distinguished by its high Curie temperature. This manuscript presents a model representing the double perovskite Sr2CrIrO6 in order to simulate and to predict its magnetic properties. This compound contains only two magnetic atoms, namely: Cr (S = 3/2) and Ir ( σ = 2 ). Our simulations are done using the Monte Carlo method under the Metropolis algorithm. We present the behavior of the magnetization and the susceptibilities as a function of the temperature. Also, we discuss the effect of the physical parameters such as the coupling exchange interactions, the crystal field and the external magnetic field. To complete this study, we have presented the ground state by exposing the different phase diagrams in different planes of the physical parameters. Moreover, we establish the magnetic hysteresis loops of this compound.

Soumia Ziti

Papers

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

Structural, electronic, magnetic properties and critical behavior of the equiatomic quaternary Heusler alloy CoFeTiSn

Characterization of the Equiatomic Quaternary Heusler Alloy ZnCdRhMn: Structural, Electronic, and Magnetic Properties

Magnetism and phase diagrams of the doubles perovskite Sr2 CrIrO6: Monte Carlo simulations

Half-metallic behavior and magnetic proprieties of the quaternary Heusler alloys YFeCrZ (Z=Al, Sb and Sn)