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This work used two approaches of mechanical alloying before high temperature solid state reaction to synthesize BaFe 12-x Sc x O 19 (x = 0.5 to 6.0) system. Rietveld refinement of X-ray diffraction patterns showed the formation of extra phases at higher Sc doping, along with the main magnetoplumbite structure. Raman spectroscopy suggested random distribution of Sc ions at the Fe-sites of hexaferrite structure. X-ray photoelectron spectroscopy (XPS) confirmed the +3 charge state at the Fe/Sc-sites. The Fe 3s band suggested dilution of ferromagnetic 3s-3d spin exchange interactions. The neutron diffraction study re-confirmed random occupancy of the non-magnetic Sc3+ ions at Fe3+ sites of the Sc doped Ba hexaferrite system. The transformation of magnetic spin order from collinear to non-collinear state has shown spin glass-like features at low temperature regime in the dc magnetization curves. This is an effect of dilution of Fe– O –Fe ferrimagnetic super exchange interactions and spin frustration in Sc-doped samples. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

In this theoretical study, we investigate novel quaternary Heusler Fe–Rh–Mn–Al alloys in the X-type structure with different types of atomic ordering in the unit cell within the spin-polarized density functional calculations. The calculations showed that the 24 possible configurations converge to the 6 nonequivalent solutions. Two types of atomic ordering with the lowest total energy Fe(4c)Rh(4d)Al(4b)Mn(4a) and Mn(4c)Al(4d)Fe(4b)Rh(4a) are half-metallic ferrimagnets in which the spin polarization at the Fermi level is close to 100 %. However, no gap is open in the majority spin projection. The following values of the total magnetic moments for these alloys were obtained: 3.01 and 3.19 μ B /f.u., respectively. In the other types of atomic ordering, the half-metallic state is not formed. In FeAlRhMn, the magnetic moment on the manganese ion compensates for the moments on the other ions, and the total moment is close to zero. In the types (MnFeRhAl, AlRhFeMn) of atomic ordering with high energies, the metallic state is also realized, and the magnetic moments on the ions are ordered ferrimagnetically. In this work, we analyzed novel quaternary alloys with different types of atomic ordering motivated by the demand for alloys with a high spin polarization, among which the FeRhAlMn and MnAlFeRh alloys were found. Both with a half-metallic ferrimagnetic state and the lowest total energy among these alloys with the same chemical composition, which indicates the stability of the half-metallic state. The other types of atomic ordering are less energetically favorable, those alloys are ferrimagnetic metals with the low spin polarization. Taking into account the half-metallic state and high spin polarization, the quaternary FeRhAlMn and MnAlFeRh alloys have prospects for use in spintronic devices. [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]

Manifold degeneracy in the zero field cooled (ZFC) state of the Ising like spin system, Ca 3 Co 2 O 6 , is progressively alleviated by magnetic field (H) at low temperature (T). Field excursion after ZFC stabilizes ferrimagnetic (FIM) state above T sf ~7K which converts to ferromagnetic (FM) state at high-H. Whereas, various metastable states have been created by H excursion of degenerate ZFC state below T sf and finally it switches to FM state. In contrast, field cooling at 5kOe supports stable FIM ordering for all temperatures in low fields, which converts to the FM state at increasingly higher-H with decrease in T. This thermomagnetic irreversibility (TMI) below ~7K indicates non-ergodic nature of the ZFC state and it persists till the system fully saturates. It is obvious that both the hindered kinetics of H-T induced first order intermediate phase to FIM transformation and interplay of different interchain interactions like 1st nearest neighbor (nn) and 2nd nn with thermal energy are playing a crucial role in appearance of such type of TMI in this spin system. [ABSTRACT FROM AUTHOR]

Multiferroic nanocomposites of x.Bi 0.95 Mn 0.05 FeO 3 + (1- x).Ni 0.5 Zn 0.5 Fe 2 O 4 , for x values of 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1, have been fabricated using sol-gel autocombustion and solid state methods. Structural and microstructural studies reveal the formation of parent phases of perovskite and spinel, while ensuring proper mixing of two phases by showing clear grain growth in the composites, respectively. Magnetic (M-H loop) measurements show that there is an enhanced magnetic order in the nanocomposites. Besides, the investigated nanocomposite materials exhibit superparamagnetic behaviour with small coercivities in the order of 3–29 Oe in all the samples. This may be due to strong influence of both the phases on one another to modify the anti-ferro magnetic (AFM) order in manganese doped bismuth ferrite. The observed magnetic behaviour was attributed to nanoparticle nature of the composites. In order to ensure the same, crystallite sizes were estimated using Langevin distribution function as well as X-ray diffractometry (XRD), which lie in the range between 28.51 and 55.43 nm, and the obtained results show a good agreement between them. The interpretations of these results are obviously evolved from the structural contributions for ferroelectricity, antiferromagnetic spin spiral cycloid structure around the FeO 6 octahedra, weak ferrimagnetic exchange interactions between the cations located at A- and B-sites and the possible interplay between different ferroic orders. [ABSTRACT FROM AUTHOR]

In this work, the Effective Field Theory (EFT) based on the probability distribution method is used to study the phase diagrams of an antiferroelectric nanowire with core/shell morphology, in the presence of a random transverse field. We have investigated the effects of the temperature, the concentration c , the surface and the interfacial couplings on the critical and the compensation behaviors (T c and T comp) of the system. The polarization, the susceptibility and the pyroelectric coefficient as a function of the temperature are examined. In addition, the phase diagrams of the nanowire are investigated in detail by modifying the system parameters. It is found that the interfacial coupling | J int / J c | shifts the random transverse field to higher values, therefore the area of the ordered phase is enlarged, which could affects the critical and the compensation temperatures. • The phase diagrams of a nanowire with antiferroelectric interfacial coupling are examined by the effective field theory. • The effect of the antiferromagnetic interfacial coupling on the critical and the compensation behaviors is studied. • The influence of the random transverse field on electric properties. • The dependence of the polarization, pyroelectric coefficient and susceptibility on the temperature are investigated. [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]

In this study, a bilayer Kagome lattice with RKKY interaction is described using a ferrimagnetic mixed spin-3/2 and spin-2 Ising model. Interesting compensation temperature and hysteresis loops of the system generated by various physical parameters, such as the crystal fields of sublattices (D a , D b), the interlayer exchange coupling (J R) and the intralayer exchange coupling (J b) are explored using Monte Carlo simulation. The results demonstrate that the compensation temperature (T comp), weaker D a and J b , and stronger D b , are favourable for the emergence of the compensation temperatures. Besides, under certain physical parameters, the system may exhibit triple-loop hysteresis behavior and multiple magnetization plateaus. • A ferrimagnetic mixed-spin (3/2, 2) Ising model on the bilayer Kagome lattice with RKKY interaction was proposed. • The effects of the crystal field, exchange coupling and non-magnetic layer were studied. • Magnetization, partial magnetization, and susceptibility were discussed. • Phase diagrams of the critical and compensation temperatures were obtained. • Interesting multi-loop hysteresis characteristics and magnetization plateaus were found. [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]

Abstract The ferrimagnetic-ferromagnetic-ferrimagnetic quaternary alloy is constructed on the Bethe lattice in the compound form as AB p C q D r and formulated in terms of the exact recursion relations in the standard-random approach. The QA is designed on the BL by placing the A atoms (spin-1) only on the sites of odd shells and randomly placing B (spin-3/2), C (spin-5/2) or D (spin-2) atoms with probabilities, or concentrations, p , q and r , respectively, on the sites of even shells. The phase diagrams are obtained from the thermal analysis of the order-parameters. It is also found that the model yields only one compensation temperature. Highlights • The ferrimagnetic‐ferromagnetic‐ferrimagnetic quaternary alloy (QA) is constructed on the Bethe lattice. • The QA is taken in the compound form as ABpCqDr and formulated in terms of exact recursion relations. • The randomization is applied in the standard‐random approach. • The A, B, C and D atoms are taken as spin‐1, spin‐3/2, spin‐5/2 and spin‐2, respectively. • The phase diagrams are studied from the thermal analysis of the order‐parameters. [ABSTRACT FROM AUTHOR]

Abstract The manganese based heusler compounds are important class of materials having remarkable ferrimagnetic and thermoelectric properties. Among them, Mn 2 RhSi which crystallizes in both Hg 2 CuTi and Cu 2 MnAl type structure have undergone detailed investigation for its electronic, magnetic and mechanical properties in Hg 2 CuTi type structure. However, no studies have been performed on Cu 2 MnAl type structure of Mn 2 RhSi. In this study we have performed a detailed comparative study on electronic, magnetic, mechanical, thermoelectric and lattice dynamical behavior of both types of Mn 2 RhSi structures. The higher value of thermal conductivity reduces the thermo electric figure of merit in the material and has large value of Seebeck coefficient making these alloys as a potential candidate for thermoelectric device application. Our results show high value of spin polarization ratio for Mn 2 RhSi which can increase the efficiency of spintronics devices which further have direct application in magnetic random access memory device. The heusler compound are least studied for their lattice dynamical behavior. In our work, we perform detail investigation on lattice dynamical behavior of both type structures of Mn 2 RhSi. Our calculations revealed the anomalous behavior of optical phonons in Cu 2 MnAl type structure which was attributed to the presence of peak right at the Fermi level in electronic density of states whereas phonon dispersion curves of Hg 2 CuTi type structure confirms its dynamical stability. Highlights • Mn 2 RhSi is half metallic ferrimagnetic material. • Positive values of Cauchy's pressure confirm the metallic & ductile nature of Mn 2 RhSi. • Positive frequencies in the PDC of Hg 2 CuTi type structure confirms the dynamical stability over Cu 2 MnAl type structure. • Large Seebeck coefficient make them suitable thermoelectric material. • Higher value of spin polarization ratio increases the efficiency of spintronics devices. [ABSTRACT FROM AUTHOR]

Monte Carlo simulation has been employed to study the hysteresis behaviors of a ferrimagnetic mixed-spin (1, 3/2) Ising nanotube with hexagonal core-shell structure. The effects of different single-ion anisotropies, exchange couplings and temperature on the hysteresis loops of the system and sublattices are discussed in detail. Multiple hysteresis loops such as triple loops have been observed in the system under certain physical parameters. It is found that the anisotropy, the exchange coupling and the temperature strongly affect the coercivities and the remanences of the system and the sublattices. Comparing our results with other theoretical and experimental studies, a satisfactory agreement can be achieved qualitatively. [ABSTRACT FROM AUTHOR]

We have investigated the temperature dependence of magnetic dynamics in a spinel-type vanadium oxide MnV 2 O 4 by inelastic neutron scattering. The scattering intensity of excitation around 20 meV disappears in the collinear intermediate-temperature cubic-ferrimagnetic phase, which reveals that this excitation should be peculiar to the orbital ordered phase. We have found a weakly dispersive mode emergent from a non-integer wavevector (1.4,1.4,0) at 56 K, which lies in the cubic-ferrimagnetic phase between non-coplanar ferrimagnetic and paramagnetic phases. This indicates that the probable presence of an incommensurate instability in the simple collinear structure. [ABSTRACT FROM AUTHOR]

Magnetization curves of ferrimagnetic mixed spin-1 and spin-2 Heisenberg chains are calculated with the help of density-matrix renormalization group method and quantum Monte Carlo simulations by considering a spin dimerization (1,2), trimerization (1,1,2) and tetramerization (1,1,1,2). The investigated mixed-spin Heisenberg chains can be alternatively viewed as a pure spin-1 Heisenberg chain, which contains at a regular lattice positions spin-2 particles. Unlike the antiferromagnetic spin-1 Heisenberg chain solely displaying a zero magnetization plateau due to the Haldane phase, the ferrimagnetic mixed spin-(1,2), spin-(1,1,2) and spin-(1,1,1,2) Heisenberg chains exhibit more striking magnetization curves involving at least two intermediate magnetization plateaux and quantum spin-liquid states. [ABSTRACT FROM AUTHOR]

CoCr 2 O 4 spinel nanoparticles synthesized by sol-gel method have been worked extensively by performing structural and magnetic characterization techniques, as well as modeling the experimental results. The microstructure analysis shows that the crystallite size of CoCr 2 O 4 nanoparticles, which are purely crystallized in cubic phase with space group Fd 3 m , is ~ 75 nm. The grain size distribution determined from scanning electron microscope images indicates that the particles are uniformly formed and distributed homogenously in the structure. A comprehensive magnetic study has been performed by measuring magnetic moment as a function of temperature and external magnetic field. The paramagnetic to ferromagnetic phase transition and non-collinear spiral magnetic transition have been observed in CoCr 2 O 4 nanoparticles at 96 and 27 K, respectively. Interestingly, we observed field-condition shift in lock-in transition which is found as 16 and 8 K for FH and FC, respectively. The exchange bias effect is observed when the CoCr 2 O 4 sample is cooled under magnetic field. The magnitude of exchange bias field decreases with increasing temperature from 5 to 50 K, and it is vanished above 50 K. In addition, we also worked on the magnetic entropy change around the paramagnetic to ferromagnetic phase transition. The magnetic entropy change is found as −0.87 J/kg K under 6 T magnetic field. [ABSTRACT FROM AUTHOR]

We use bond operator method to study the dimerized ferrimagnetic spin chain. With the dimerization parameter g from 1 to 0, the model describes the system from normal ferrimagnetic state to dimer state. From the energy spectrums, the system energy is changed from ferrimagnetic spectrum to large energy gap at bond state. At finite temperature, the uniform susceptibility, internal energy and specific heat are calculated respectively with different dimerization parameters g . These results qualitatively agree with the numerical results of other methods quite well. [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]

The hysteresis properties of a kinetic mixed spin (1/2, 1) Ising ferrimagnetic system on a hexagonal lattice are studied by means of the dynamic mean field theory. In the present study, the effects of the nearest-neighbor interaction, temperature, frequency of oscillating magnetic field and the exchange anisotropy on the hysteresis properties of the kinetic system are discussed in detail. A number of interesting phenomena such as the shape of hysteresis loops with one, two, three and inverted-hysteresis/proteresis (butterfly shape hysteresis) have been obtained. Finally, the obtained results are compared with some experimental and theoretical results and a qualitatively good agreement is found. [ABSTRACT FROM AUTHOR]

By using Monte Carlo simulations for classical Heisenberg spins, we study the critical phenomena and ferrimagnetic properties of spherical nanoparticles with core-shell geometry. The particle core is composed of ferromagnetic spins, and it is coated by a ferromagnetic shell. Total size of the particle is fixed but the thickness of the shell is varied in such a way that the shell layer is grown at the expense of the core. Effects of the shell thickness, as well as dynamic magnetic field parameters such as oscillation period and field amplitude on the magnetization profiles, dynamic hysteresis loops and phase diagrams have been investigated for the present system. It has been found that as the shell thickness varies then the easy axis magnetization of the overall system may exhibit Q -, P -, L - and N - type behaviors based on the Neél terminology. We also found that three distinct anomalies originate in the thermal variation of specific heat with increasing field period. Dynamic hysteresis loops corresponding to off-axial magnetization components exhibit unconventional behavior such as double rings with symmetric shapes around the vertical axis over the h ( t ) = 0 line which may originate due to the stochastic resonance behavior of these components. [ABSTRACT FROM AUTHOR]

The hysteresis properties and phase diagrams of a ternary nanowire, composed of a ferromagnetic (FM) core of spin-1 encircled by a ferrimagnetic (FiM) shell of mixed spin-(1/2, 3/2). Monte Carlo simulation is used to study the effects of the exchange interactions (R s , R 1 , R 2 and R I F) and crystal fields (D c , D s) on the phase diagrams for various thicknesses of core and shell of the system. Our outcomes indicate that the compensation temperature exists for a particular range when D c and D s are present. In addition, a first and a second order phase transitions appear for different values of D c , while a second phase transition appears for various values of D s. Moreover, the hysteresis loops, coercivities and remanences of the system and three sublattices are discussed in detail. Multiple hysteresis loops such as double, triple and quintuple loops were found in the system for a various physical parameters. By comparing our findings to those of previous theoretical and experimental studies, a qualitative agreement can be found. [ABSTRACT FROM AUTHOR]

This work reads on the obtainment of the strontium hexaferrite substituted with neodymium in its pure phase using the solid state reaction method. The solubility of neodymium on the strontium hexaferrite was investigated according with the formula Sr 1−x Nd x Fe 12 O 19 , for x=0.00, 0.05, 0.10, 0.15, 0.20 and 0.25. Results indicate that neodymium is soluble in the hexaferrite until x=0.15. In samples with higher neodymium content there are traces of secondary phases. Analysis of magnetic and structural properties was performed in function of the neodymium content, always in its solubility range. From the structural properties, it was observed that the addition of a little neodymium quantity in the Sr-hexaferrite causes an important reduction of the unit cell volume. Also, magnetic properties are strongly linked to the structural behavior, in this case a trend to reduce the magnetization of the samples was detected when neodymium content increased, which can be explained in terms of fluctuations of the superexchange coupling conducted by the neodymium interactions with the structure. Mössbauer analysis was carried out in order to analyze the effects of the neodymium substitution on the hyperfine parameters, as well as to confirm the preferential site of the neodymium substitution in the Sr-hexaferrite. [ABSTRACT FROM AUTHOR]

A mixed spin-2 ( F e І І ) and spin-5/2 ( F e І І І ) ferrimagnetic Ising model on a honeycomb lattice was built to describe the F e І І F e І І І bimetallic oxalates, and the ferrimagnetic ordering behaviors and compensation temperatures were investigated through the effective-field theory based on Glauber-type stochastic dynamic. It was found that the effects of the interlayer coupling and the single-ion anisotropy contributed to the increase of the critical temperature with growing layer separation and the existence of compensation temperature depending on the organic cation. In particular, the magnetization of the system may show a small discontinuous jump in a certain range of the single-ion anisotropy. [ABSTRACT FROM AUTHOR]

Microstructural, magnetic and dielectric properties of Ni x Cu 1-3 x Zn 2 x Fe 2 O 4 nanoparticles were investigated by various techniques. Samples were structurally analyzed using X-ray diffraction and Rietveld refinement. A structural phase transition from a tetragonal spinel structure with space group I 4 1 / amd to a cubic spinel structure with space group Fd 3 ‾ m was observed by increasing the Ni/Zn co-substitution and also the lattice parameter increases. These structural results were confirmed by Raman and Fourier-transform infrared spectroscopy. The magnetic hysteresis loops of the samples indicated a magnetic phase transition from the hard to soft ferrimagnetic and the magnetization values increase for x up to 0.2, and then it decreased. The results of impedance analysis indicated that the increase in the mobility of charge carriers in the samples with x between 0 and 0.15 can be attributed to the reduced porosity and surface area, because a smaller number of defects commonly would block the movement of carriers. [ABSTRACT FROM AUTHOR]

The probability distribution technique, exploited within the framework of effective field theory and the Ising model, was used to study the magnetic and thermal properties of a nanowire assimilated to a hexagonal shaped system of a core–shell structure and with mixed spins (3 / 2 , 2) , respectively. The coupling between core and shell is ferrimagnetic. Under certain physical parameter values, the nanowire exhibits the compensation behavior. The hysteresis behavior was investigated in the presence of an external magnetic field by magnetizing and demagnetizing the nanowire, as well as the effects of single ion anisotropy, ferrimagnetic exchange interactions and temperature on hysteresis loops. The dependence of the shapes of loops on the physical parameters of the system has been elucidated. At low temperatures, the nanowire exhibits triple, quadruple, quintuple, sextuple, septuple and nonuple hysteresis loop behaviors, which have important technological applications. Furthermore, the thermodynamic properties of the nanowire was also studied by evaluating the susceptibility, the internal energy and specific heat for a variety of system physical parameters. [ABSTRACT FROM AUTHOR]

A method for calculating micromagnetic state of ferro- or ferrimagnetic single-crystals based on the Néel's method of phases is proposed. The standard Néel technique requires different approaches to calculation of micromagnetic state of samples with different anisotropy types. Furthermore, this technique cannot be used to calculate magnetization curves of materials with a complex anisotropy type, in which the first-order magnetization process (FOMP) occurs. On the contrary, the technique proposed in the present work makes it possible to calculate micromagnetic state of a sample within one unified approach. This technique has no limitations in terms of the anisotropy type as well. In case of the FOMP, the simulation methods that we used show results different from conventional calculation methods. The reason is that the conventional methods imply coherent rotation of magnetization in single domain particle (so-called Stoner–Wohlfarth model). We explain this discrepancy by the fact that a magnetic domain structure appears in the region of the FOMP. In the present work we show that magnetization processes do not occur in a jump under the FOMP but gradually pass though nucleation and new high-field phase growing, which substitutes for the low-field phase. [ABSTRACT FROM AUTHOR]

The dimerized ferrimagnetic spin chain has been approached both in the presence and absence of the external magnetic field by using the Villain transformation. Two branches of the low-lying energy modes have been presented and the upper branch of the mode demonstrates the exotic omega-shape when the dimerization parameter is greater than 0.6. We also find that the competition between magnetic field and the dimerization parameter also contribute the omega-shape in lower branch mode. Thermodynamic quantities like free energy, specific heat, magnetization, and susceptibility in finite temperature and magnetic field with different dimerization parameters have also been presented. [ABSTRACT FROM AUTHOR]

We investigate the spin excitation spectrum and the thermodynamic properties of the XXZ anisotropic ferrimagnetic spin-(1/2, 1) chain under the presence of a magnetic field using the Villain transformation method. The effect of the XXZ anisotropic parameter and external magnetic field on the thermodynamic observables are calculated at finite temperature. The energy spectra exhibit the coexistence of a gapless branch and a gapful branch, both of them are sensitive to the change of XXZ anisotropic parameter. The gapless branch exhibits a V-shape structure, while the gapful branch is reversed and presents an omega-shape for the XY model which is completely different from previous results for the XXZ model. Thermodynamic quantities such as free energy, internal energy, entropy, specific heat and magnetization are present. These findings for the isotropic case are compared with the results calculated by the other established methods and it turns out that Villain transformation well describes this system at low temperature. • The spin excitation spectrum and thermodynamic properties of the XXZ anisotropic ferrimagetic spin-(1/2, 1) chain under the presence of magnetic field are investigated by the Villain transformation method. • Two branches of the excitation energy spectra are obtained, which are sensitive to the size of the XXZ anisotropic parameter. • The gapless branch exhibits a V-shape structure, while the higher branch is reversed and exhibits an omega-shape structure for the XY model. • The dependence of the thermodynamic quantities on the XXZ anisotropic parameter and magnetic field are studied. [ABSTRACT FROM AUTHOR]

Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse field in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors. [ABSTRACT FROM AUTHOR]

Abstract: By using the Villain transformation, the Heisenberg ferrimagnetic spin chain with anisotropy as well as an external field is explored. We obtain two branches of the low-lying excitation spectrum with the presence of magnetic field. The thermodynamic quantities, like free energy, specific heat and magnetization at finite temperature, are calculated. And the effects of the anisotropy parameter on these thermodynamic quantities are explicitly discussed. The results show that a phase transition may occur at the critical value of anisotropy . [Copyright &y& Elsevier]

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]

In this work we present an exact Bessel function solution to the variation equations for a ground state of the chiral Hamiltonians in the continuum limit for cylindrical symmetry. The solution imposes no constraints on the magnetic spin moment magnitude. The formulation is consistent with the generalized view of U. K. Roessler et al. Nature 442, 797–801 (2006) that both the magnetic moment amplitude and magnetic stiffness ratio are micromagnetic properties and variations in amplitude may be allowed. With the exact solutions, we reveal that the added stabilization energy of the 2D skyrmion relative to the 1D solution is the result of the cylindrical symmetry rather than specifics of the chiral interactions. The methods can be employed to understand Bloch type magnetic spin textures observed in MnSi and FeGe and Néel type magnetization textures in antiferromagnetic dielectrics and ferrimagnetic thin sheets with the application of an electric field. • The Bessel function solutions are exact solutions of chiral Hamiltonians that predict the skyrmion magnetic spin structures. • The Bessel function solutions may be used to interpret both Bloch and Neel type spin textures. • The exact solutions reveal the stabilization energy of the 2D skyrmion is entirely the result of cylindrical symmetry. • The exact solutions predict skyrmion radii of 3.8 reciprocal wave numbers in good agreement with U. K. Roessler et al., Nature, 442, 797-801 (2006). [ABSTRACT FROM AUTHOR]

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]

By using the method of Dyson–Maleev mean-field theory, we study the effect of bond alternation and longitudinal magnetic field in the model of ferrimagnetic spin chain. Based on the numerical results of self-consistent equations, properties of the excited spectrums, magnon internal energy, static susceptibility, magnetization plateau and specific heat are obtained with different bond alternation parameters δ and external magnetic field B. This method provides qualitative consistent results to describe the phase from ferrimagnetic state to bond altered state. • The transition from ferrimagnetic to dimer state can be described by Dyson-Maleev theory. • The quantum magnetization plateau of mixed spin chain can be tuned by bond alternation parameter. • The result of Dyson-Maleev theory is qualitatively consistent with other numerical method. [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]