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In this study we are investigating the effect of pressure and tetragonal distortion of Co 2 FeGa full Heusler compound in L2 1 and XA structures on the elastic, magnetic and thermomagnetic properties. Our approach for this is by using density functional theory (DFT) and Monte Carlo (MC) simulation. Our result reveals a significant effect of pressure on the magnetization and Curie temperature on both prototypes. The elastic constants calculated here determine the stable configuration on both structures. The exchange interaction is also influenced by the pressure. The same sort of behavior of the effect of tetragonal distortion is seen on the elastic constants, magnetization, and exchange interaction. Therefore, a detailed significant effect is found in this work and compared to previous studied. [ABSTRACT FROM AUTHOR]

• Magnetocrystalline anisotropy (MCA) increases when nitrogen is doped in the center of Pt layer. • MCA decreases when oxygen is doped in the center of Pt layer. • MCA decreases when nitrogen is doped in the center of Fe layer. • MCA decreases when oxygen is doped in the center of Fe layer. We studied the magnetic and electronic properties of L 1 0 -FePt alloy interstitial doped by oxygen or nitrogen using tetragonal distortion. We applied the density functional theory from first principle until the exchange–correlation energy; the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) was used. We found that the magnetocrystalline anisotropy MCA significantly increased for FePt:N Pt and our obtained value was 3.879 meV, which exceeds the pristine value. The anisotropy field H a , saturation magnetization M s and the energy product B H m a x were nearly close to the pristine value. These parameters can be tuned for practical applications. Calculations of formation energy E for reveal promotion of stability with doping. Density of state calculations showed strong hybridization of d -orbits with 2 p orbits of O or N. Moreover, with doping, there was an enhancement of energy states at Fermi level. [ABSTRACT FROM AUTHOR]

We have studied the effects of oxygen and nitrogen doping as interstitial defects on the structure and magnetic properties of CoNi alloy using the first principle density functional theory, where we include the orbital-spin interaction in the calculations. Our calculations reveal that the CoNi:O Ni in the L1 0 -structure has a large enhancement in the saturation magnetization (M s) and a small reduction in the magnetic crystalline anisotropy (MCA). For CoNi:O Co , we found a small reduction in M s and MCA. However, for CoNi:N Co and CoNi:NNi there is always a reduction in M s and MCA. Therefore, the first alloy could be suitable for permanent magnets. A detailed analysis of other parameters, such as the magnetic hardness parameter (κ), optimum supercell parameters, anisotropy field (H a) , and formation energy (E f o r ) is presented. The interstitial oxygen doping enhances the magnetic properties. • The structural and magnetic properties of CoNi:D using the first principle are presented. • A large enhancement in the saturation magnetization has been predicted when adding oxygen. • The interstitial defect reduces the saturation magnetization and magnetocrystalline anisotropy energy. • These defective alloys are a potential candidate for permanent magnets. [ABSTRACT FROM AUTHOR]

• The critical temperature of FeNi and FePt alloys using Heisenberg interaction is closer to the experimental value than the Ising interaction. • The FeNi and FePt alloys prefer a ferromagnetic phase over the ferrimagnatic phase. • The Ising interaction predicts higher critical temperature for the FeNi alloy than the Heisenberg interaction. • The Heisenberg interaction predicts higher critical temperature for the FePt alloy than the Ising interaction. A Monte Carlo simulation has been used to explore the magnetic properties of L1 0 ordered FeNi and FePt binary alloys. Our Hamiltonians include Heisenberg interaction or Ising interaction. Our calculations of variations of specific heat C v , magnetic susceptibility χ and the magnetization M with the temperature T showed that predicted critical temperature for ferromagnetic phase is very close to the experimental values for these alloys. Also, thermal hysteresis loops, magnetic remanence, and the coercive field have been calculated. Moreover, the magnetic properties of the ferrimagnetic phase are presented. [ABSTRACT FROM AUTHOR]

Monte Carlo simulation has been performed to explore the compensation temperature and the critical behavior on a triple layer spin (1-1/2-1) cubic system with ferrimagnetic coupling at the two interfaces. Our results showed that the compensation temperature T c o m p is less influenced by increasing the number of layers or the exchange coupling of the spin 1 2 layer. Gradual increases in the critical temperature T c is shown with increasing the exchange coupling in spin 1 layers or spin 1 2 layer. Finally, the above results have been confirmed by the simulation performed on the heat capacity and Binder cumulant. • The compensation temperature is less influenced by increasing the number of layers. • Compensation temperature disappears for specific values of exchange interaction. • Gradual increases in the critical temperature with increasing the exchange coupling. • Compensation temperature disappears for specific values of exchange interaction. [ABSTRACT FROM AUTHOR]

Monte Carlo simulation has been applied to study the thermal and magnetic properties of the inverse spinel-like structure, copper fluoride as an example, of spin 1/2 - spin 1 Ising interactions. Our calculations of the magnetization as a function of temperature shows compensation for low values of coupling strength between spin-1 type atoms (J 1) in the same layer, low absolute value of coupling strength between the layers of different spin type (J 3), and large values of coupling strength between spin-1/2 (J 2). The transition from ferrimagnetic to paramagnetic phase is observed at the critical temperature T c. In addition, T c increases slowly at different values of the exchange interaction. Regarding the anisotropy field D on spin 1 state, our results show a threshold value of −0.3 for the compensation to appear. Finally, our results are applicable to the Cu 2 F 5 compound which has d8 and d9 electron configurations. • The compensation temperature in the ferrimagnetic phase depends on the strength of the spin-spin interactions • Compensation occurs for small values of coupling strength of the same type atoms • Compensation occurs for large values of coupling strength of the different type atoms • An itinerant region has been revealed between the compensation and critical temperatures. [ABSTRACT FROM AUTHOR]

Density Functional Theory and Monte Carlo Simulation were used to study the electronic and magnetic properties of X 3 Pt and XPt 3 binary alloys (where X = Fe, Co, or Ni), possessing L1 2 structure. Our results were carried out using a ferromagnetic phase for these binary alloys and showed a Curie temperature (T c) above room temperature for X 3 Pt and below room temperature for XPt 3. We calculated the exchange interactions J x x , J x P t , and J P t P t and found that J N i N i in the Ni 3 Pt compound was the strongest. Finally, we calculated the magnetocrystalline anisotropy for these alloys. • Electronic and magnetic properties of X3Pt and XPt3 binary alloys are studied using Density functional theory and Monte Carlo simulation. • Our results indicate that Curie temperature (T c) is above room temperature for X3Pt and below room temperature for XPt3 • The exchange interactions J x x , J x P t and J P t P t are studied and revealed that J N i N i in N i 3 P t is the strongest. • Weak hybridization between X-3d and Pt-5d orbitals near Fermi energy and strong hybridization between Pt-5d orbital and X-3d are observed. [ABSTRACT FROM AUTHOR]

• Mixed spin Ising model on a checkerboard square structure was proposed. • The effect of crystal field and exchange coupling were studied. • The phase diagrams of the critical and compensation temperatures were presented. • Double-loop hysteresis behaviors were found. The magnetic properties and phase diagrams of the mixed spin-1 and spin-1/2 Ising model on a checkerboard square structure have been studied using the Monte Carlo simulations based on the Metropolis update protocol. The system consists of four quartets of alternative spin configurations. We found that the compensation temperature evolves for J 1 <0.6 of the spin-1 assembly and J 2 >1.6 of spin-1/2. Regarding the crystal field strength, a threshold value of D > - 0.8 has been observed. We obtain the N -, Q - and P -type compensation behaviors in the system. The phase diagrams exhibit a second-order phase transition to a paramagnetic phase for small values of D ; hence, the system does not show the tricritical point. However, for large negative values of D a first-order phase transition occurs at the threshold value of J 1. The magnetic hysteresis cycles have been obtained for different values of the exchange interaction, temperature, and crystal field. Finally, the system exhibits the superparamagnetic behavior for a fixed value of the temperature and crystal field. [ABSTRACT FROM AUTHOR]