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We used Monte Carlo simulation to study the magnetic properties and compensation behavior of a ferrimagnetic mixed-spin (3 / 2 ; 1 / 2) Ising system in a graphene bilayer. The effects of exchange interactions, crystal field, external magnetic field and temperature on the total magnetization, partial magnetizations, magnetic susceptibility, phase diagram and hysteresis behavior of the system were examined. Interesting results were obtained in this work, such as the compensation behavior and the multi-loop hysteresis phenomenon for specific values of the system's physical parameters. Our results conform to those of other theoretical studies. • The compensation and critical behaviors of a Graphene Bilayer were investigated. • Different total magnetization profiles are observed in this ferrimagnetic system. • The effect of various physical parameters on hysteresis behavior was presented. [ABSTRACT FROM AUTHOR]

Ab initio calculations are used in the present study to analyze the structural, magnetoelectronic, mechanical, thermal, thermoelectric, optical and thermodynamic properties of AMnBi 2 compounds (where A = Ca and Sr). The calculations use the density functional theory involving the Full Potential –Linearized Augmented Plane. Wave and the Monte Carlo simulation. We have used the Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) functional for modelling the exchange-correlation potential with Hubbard correction (GGA + U) was employed. The bulk modulus, its first derivative, and the optimal lattice parameters have been found. Both compounds display metallic nature. The electronic transport coefficients have been calculated. The entropy, thermal expansion coefficient, Debye temperature, and heat capacities C v and C p are calculated. The elastic constants at zero pressure, the bulk modulus B, and the shear modulus G have been evaluated. The Young's modulus and Poisson's ratio of two compounds have been performed. The Debye temperature is also approximated from the average sound velocity. The Néel temperature, magnetization, and hysteresis cycles are found. [ABSTRACT FROM AUTHOR]

We report the structural stability and half-metallicity of the half-Heusler alloy CoMnSe via the density functional theory (DFT). The γ -phase ferromagnetic of CoMnSe is more energetically stable than other phases. The electronic and magnetic properties show that the CoMnSe is a false half-metal ferromagnetic with 98.10% spin polarization and a total magnetic moment of 4 μ B . This value is in good agreement with the Slater-Pauling rule and available data using the GGA method, whereas the GGA+U method shows it is a ferrimagnetic metal with 95.73% spin polarization, and the total magnetic moment is 4.01 μ B. The effects of Bulk strain and axial strain demonstrate that the relative change of total magnetic moment M t o t and spin polarization P of CoMnSe is almost negligible, indicating that the half-metallicity is strong against Bulk strain and axial strain. Using Monte Carlo simulations, a transition ferromagnetic-paramagnetic response is also studied. • CoMnSe alloy is mechanically and thermodynamically stable. • CoMnSe does not undergo martensitic transformation. • CoMnSe is found to be falsely half-metallic using GGA, while it is metallic using GGA+U. • The high spin polarization and Curie temperature make CoMnSe suitable for spintronic. [ABSTRACT FROM AUTHOR]

The ferrite having the general chemical formula Mg 1-x Zn x Fe 2-x Cr x O 4 (x = 0.0, 0.1, 0.3, 0.5 and 0.7) prepared by the solid state technique. The XRD analysis depicted the presence of single phase cubic spinel structure. They showed an increasing trend of lattice parameter with the expansion of the spinel lattice which resulted from the partial incorporation of larger radii. The FT-IR absorption bands are observed at 590 and 430 cm−1 for tetrahedral and octahedral location. These bands are shifting toward 604.7 and 474.15 cm−1 for Zn–Cr substitution due to the change in Me–O covalence. DC electrical resistivity has found to show the highest magnitude 107 Ω cm at x = 0.1, decreases with further increase in content. The hysteresis curves measured at 300 K demonstrate the coercivity and it varies from 146.33 to 9.427 Oe for increasing the content which confirms decreasing the grain size as well as soft ferrimagnetic material. • XRD patterns revealed that the cubic spinel structure and pure phased. • The FT-IR spectrum shows characteristic features of spinel structure. • The maximum saturation magnetization value (58.718 emu/g) registered at x = 0.1. • DC electrical resistivity has found to show the highest magnitude 107 Ω cm at x = 0.1. [ABSTRACT FROM AUTHOR]

In this work, we study the magnetic properties of a borophene core-shell structure with spins σ = 5/2 and S = 3/2, using Monte Carlo simulations. We start by discussing the ground state phase diagrams corresponding to several physical parameters. Then the magnetizations and the susceptibilities have been analyzed. Besides, we explore the thermal magnetization behavior under the effect of the reduced exchange coupling interactions. Furthermore, we investigate the presence of the compensation temperature induced by the presence of a core shell structure and resulted from the variation of the reduced coefficient coupling. Finally, the variation of the total magnetizations as a function of the reduced exchange coupling interactions, the crystal and the external fields has been discussed. • Monte Carlo Simulations is used to investigate the magnetic properties of the core-shell Borophene. • The ground state phase diagrams are established. • The effect of exchange coupling interactions and magnetic external and crystal fields are analyzed. • The existence of compensation Temperature is studied. • The hysteresis cycles are explored. [ABSTRACT FROM AUTHOR]

Magnetic properties of a superlattice that consists of three square layers with Ising spins σ = 1 / 2 , s = 1 and q = 5 / 2 , are investigated by means of standard Monte Carlo simulations and Mean Field Theory. The Hamiltonian model comprises contributions of intralayer and interlayer exchange interactions and the applied external magnetic field. Effects of the external magnetic field on magnetic behaviors have been thoroughly studied in the presence of thermal excitation. Ground state and thermal phase diagrams are numerically computated by both methods. Ground state phase diagrams of the system exhibit one ferromagnetic phase (1/2, 1, 5/2) and three ferrimagnetic ones: (−1/2, 1, 5/2), (−1/2, −1, 5/2) and (−1/2, 1, −5/2). A number of interesting phase diagrams and phenomena have been found, including hysteresis behaviors. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties have been investigated in the magnetic composites of hard magnetic Barium hexaferrite (BHF) and soft magnetic Ni–Mn–Sn Heusler alloy. The magnetic composites undergo two distinct ferromagnetic to paramagnetic and ferrimagnetic to paramagnetic phase transitions corresponding to alloy and BHF phases, respectively. Magnetic biasing between the hard and soft magnetic phases has been observed in the composites when both the phases are in the ferromagnetic ordering i.e., a squeezing in the magnetic hysteresis curve is observed around H = 0. The squeezing effect may be used in the magnetic memory device application where an optimum coercivity, high remanent magnetization, and high squareness ratio are required. On the other hand, the composites show high magnetocaloric effect with a constant high value of magnetic entropy changes between the two successive magnetic transitions. This gives an advantage with wide working temperature in the magnetocaloric application. • Magnetic composite of soft magnet Ni 1.8 Mn 1.2 Sn and hard magnetic BaFe 12 O 19. • Magnetic biasing i.e., a squeezing in the M-H curve around H = 0. • Squeezing effect in the magnetic memory device application. • Constant high magnetic entropy changes between the two magnetic transitions. • Potential material for magnetocaloric application with wide working temperature. [ABSTRACT FROM AUTHOR]

In the present work, nanocrystalline Ni x Co 1- x Fe 2 O 4 oxides with average crystallite size between 11 nm and 111 nm have been analyzed by Mössbauer spectroscopy, hysteresis loops, field cooled (FC) and zero field cooled (ZFC) magnetization measurements. A core-shell model has been proposed. Accordingly, the Mössbauer spectra evidence a ferrimagnetic core and a disordered shell (spin-glass), the latter increasing with Ni concentration. Hysteresis curves reveal the ferromagnetic nature of the investigated compounds and transformation from single-to multi-domain behaviour at a critical particle size dependent on Ni2+ ion concentration. The magnetic properties of finest powders (average crystallite size ∼ 11 nm) are the most sensitive to the Ni2+ ions content. A general increase in the coercive field, H C , with reducing temperature according to the modified Kneller's formula H c (T) = H c (0)[1-(T/T B) β where β = 0.45 occurs. A high saturation magnetization of about 90 emu/g and an increase in H C from about 0.3 kOe at 300 K to 7 kOe at 10 K have been observed for the sample Ni 0.1 Co 0.9 Fe 2 O 4 (x = 0.1). Increasing magnetization and coercive field with reducing temperature are also explained within the core shell model. FC and ZFC data show strong dependence of the magnetic properties on crystallite size and concentration of Ni2+ ions. • NixCo 1−x Fe 2 O 4 nanoparticle successfully synthesized via the glycol-thermal method. • The transformation from single-to multi-domain was observed at critical particle diameter and was dependent on composition. • Magnetization properties are dependent on particle sizes and annealing temperature. • Magnetic disorder was observed at measuring temperatures lower than 100 K due to different magnetic phases. • FC and ZFC curves showed strong dependence on Ni2+ ion concentration. [ABSTRACT FROM AUTHOR]

An effective field method has been employed to study the magnetic properties of a ferrimagnetic mixed-spin Ising trilayer nanographene structure. The system is formed by alternate layers of two different spins atoms A (spin-1) and B (spin-½) arranged in a particular fashion A – B – A for which the nearest-neighbor spins of each layer are coupled ferromagnetically (J A and J B), whereas the cross atom interaction A - B (interlayer) is antiferromagnetic (J AB). We examined the effects of interlayer (or intra-layer) exchange coupling and single-ion anisotropy on the magnetization curves of the system. We found that the antiferromagnetic inter-layers (J AB < 0) coupling and the single-ion anisotropy have a dominant factor in the occurrence of the single or the double compensation temperature. We also deeply examined the occurrence of hysteresis loops and their various unusual forms. The results obtained are discussed in detail as a function of the main parameters of the magnetic Hamiltonian. Finally, we noticed that our results are in line with other recently reported theoretical and numerical studies. • Ferrimagnetic spin mixed with nano-graphene trilayer Ising model on effective field approach has been considered. • Effects of Intra- and inter-layers exchange couplings, as well as single-ion anisotropy have been analyzed. • One or more compensation points can be obtained under special choice of intrinsic parameters. • The shape and the multi-windows hysteresis loops can be controlled through exchange or single-ion anisotropy. • Application of synthetic ferrimagnetic multilayers are outlined. [ABSTRACT FROM AUTHOR]

Abstract: We have synthesized polycrystalline samples of the series of double-perovskite (DP) type structure . Their structural and magnetic properties were investigated by experiments of X-ray powder diffraction, magnetic susceptibility and electrical resistivity. Both series crystallize in a monoclinic structure, space group (rather than in the triclinic ), with a significant degree of Fe/Ir cationic disorder. Interestingly, our results indicate a change in the nature of the microscopic magnetic interaction induced by La doping, where the system seems to evolve from antiferromagnetic in the extremities of the series, and 2.0, to ferrimagnetic for intermediate regions of the series. In this work we focus on the comparison of the physical properties of two representative compounds of these families, and , which exhibit the higher magnetization within their series. For the Ca-based sample the disorder is around 34% while was found to be roughly for the compound. [Copyright &y& Elsevier]

Magnetic properties of a trilayer nanostructure of hexagonal lattices described by the spin-1/2 Ising model are investigated via the effective-field theory (EFT) with correlations. In order to clarify the distinction between the ferromagnetic and ferrimagnetic behaviors, the total magnetization, total susceptibility, total inverse susceptibility and critical boundaries have been obtained for positive and negative interlayers couplings. From thermal variations, some magnetic compensation types are found for the ferrimagnetic system. The specificities of the susceptibilities when the magnetizations present compensation temperatures have been also studied. • Correlation identities on a nanostructure of hexagonal lattices are obtained. • From the spin correlation identities the effective-field theory is applied. • The total magnetization and total susceptibility are obtained. • The critical temperature and the compensation temperature are investigated. [ABSTRACT FROM AUTHOR]

This paper presents the study of the magnetic properties exhibited by a highly porous strontium ferrite with a copper metal cover. The analyzed samples consisted of a mix of the M − and X-type ferrimagnetic phases. The characterization included optical microscopy, X-ray diffraction, and the Rietveld refinement method. Microstructural characteristics and magnetic properties were studied at different amounts of electrodeposited copper. Results show the emergence of strong ferrimagnetic coupling between the M and the X phases, whereas the copper layer enhances the squareness remanence (M r / M s). A reduction in the width of the switching field distribution (SFD) curves observed in the porous structures indicates an intense competition between the exchange and magnetostatic interactions, which results in the emergence of a cooperative switching of the particles. This interesting phenomenon is a product of a conjunction of the porous structure together with the ferrimagnetic coupling of the ferrimagnetic phases. • Strong ferrimagnetic interaction generated in mixed M and X-type ferrite. • Copper electrodeposition on the hexagonal ferrite surface. • Magnetic properties of a highly porous ferrite covered with copper. • Analysis of the competence of the magnetic interactions by SFD curves. [ABSTRACT FROM AUTHOR]

In this paper, the magnetic properties of a bi-layer graphyne structure have been studied using Monte Carlo simulations. The considered system is composed of two planes of graphyne with mixed spins: σ = 7/2 and S = 1. Firstly, the ground state phase diagrams for zero temperature are reported and discussed. Secondly, the magnetic properties for the studied system are examined for non-zero temperature. The effects of exchange coupling interaction and temperature on magnetization, susceptibility and transitional temperature. Furthermore, the effects of the crystal field on total magnetization of the system have been exhibited. Finally, the effect of the ferrimagnetic parameter, temperature and crystal field on the hysteresis cycles have been determined. The obtained results have been compared with theoretical and experimental researches. • We study the magnetic properties of a bi-layer graphyne structure. • The ground state phase diagrams are presented and discussed. • The magnetic properties of a bi-layer graphyne structure using Monte Carlo simulations are investigated. • The hysteresis cycles of a bi-layer graphyne structure are analyzed. [ABSTRACT FROM AUTHOR]

Magnetic transition metal oxides are interesting candidates for both academic as well as industrial researches. In the present work, we study the influence of partial Mn doping on structural and magnetic and dielectric properties of α-Fe 2 O 3 using x-ray and neutron diffraction, magnetization and dielectric measurements. In particular, this paper deals structural, magnetic and dielectric properties of Fe 1.95 Mn 0.05 O 3. The compound is found to crystallize in corundum type (α-Al 2 O 3) having rhombohedral lattice structure with hexagonal setting in the space group (R- 3 c). It is seen that partial substitution of Fe by Mn in α-Fe 2 O 3 (known as hematite) drastically alters the Morin transition in the hematite compound by reducing the ordering temperature from a value of 260 K to about 220 K. Information about ferrimagnetic structure of Fe 1.95 Mn 0.05 O 3 has been obtained from the magnetic part of the neutron diffraction analysis. The results of room temperature neutron diffraction, temperature dependent magnetization and dielectric studies are reported and discussed in the present work in order to understand the correlation between structure and magnetism in this compound and ways in which magnetism and other physical properties can be controlled. [ABSTRACT FROM AUTHOR]