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In this study, a bilayer zigzag graphyne nanoribbon with RKKY interaction is described using a ferrimagnetic mixed-spin (2, 5/2) Ising model. The compensation behaviors and hysteresis characteristics of the system generated by various physical parameters, such as crystal fields of sublattices, interlayer exchange coupling and the intralayer exchange coupling are explored using Monte Carlo simulation. In the research results, we found that among the 30 possible spin configurations that may occur in the ground state of the system, only 21 spin configurations are stable. At the same time, under certain parameters, the system exhibit interesting behaviors such as compensation phenomena and multi-loop hysteresis. This can provide a theoretical reference for multi-state magnetic recording. • Ising model and Monte Carlo method were used to study the bilayer zigzag graphyne nanoribbon. • The effect of RKKY interaction on the magnetic properties of the graphyne was investigated. • The ground-state phase diagram, magnetization, magnetic susceptibility were obtained. • Phase diagrams and hysteresis loop of the system were presented. • Interesting behaviors of compensation temperatures and multi-loop hysteresis were found under certain parameters. [ABSTRACT FROM AUTHOR]

This study investigates the magnetocaloric potential of the Al 50 Cr 21-x Mn 17+x Co 12 (x=0, 4, 8 at%) high-entropy alloy (HEA) series using integrated experimental and theoretical approaches. Structural analysis by X-ray diffraction and scanning electron microscopy indicate a dual phase containing B2 and body-centered cubic (BCC) structures. Magnetic characterization shows an approximately linear decrease in saturation magnetization and Curie temperature with increasing Cr content. Curie temperatures calculated by Monte Carlo simulations suggest that the measured magnetic properties originate from the B2 phase rather than the BCC phase. The enhanced magnetocaloric effect with decreasing Cr content highlights the attractiveness of HEAs in magnetocaloric applications. • Al 50 Cr 21-x Mn 17+x Co 12 (x=0, 4, 8 at%) high-entropy alloys were prepared by arc melting. • The phase and chemical composition analysis indicates a dual phase containing B2 and BCC structures. • Calculated T C s suggest that the measured magnetic properties originate from the B2 phase rather than the BCC phase. • Tunable TC and magnetization with decreasing Cr were confirmed through measurement of TC and hysteresis loops. • The magnetocaloric effect was quantified by measuring the adiabatic temperature change and magnetic entropy change. [ABSTRACT FROM AUTHOR]

The composition dependent magnetic structure in epitaxial BaFe 12-x Sc x O 19 (0 ≤ x ≤ 2.1, BaScM) thin films have been investigated. Results show that with increasing Sc3+ content, the out-of-plane c -axis lattice constants of BaScM films increase but do not follow the Vegard's law. The changes in hysteresis loops indicate a variation of magneto-crystalline anisotropy from the uniaxial-type for BaFe 12 O 19 to the near-planar type for BaFe 10.2 Sc 1.8 O 19. The remanent magnetic domains change from a mixture of dots and maze-like structure to more maze-like structure as the Sc3+ content increases. The above magnetic results can be explained by a composition dependent magnetic structure transition from collinear-type ferrimagnetic magnetic structure to the non-collinear conical magnetic structure which appears at Sc3+ content x ≥ 0.6. The ZFC/FC curves further show that the conical magnetic structure transition temperature (T cone) of the films increases with the Sc3+ content until x ≥ 2.1. The above results may help better apply BaScM films in the electromagnetic devices. • With increasing Sc3+ content, lattice constant c increases but doesn't follow the Vegard's law. • With increasing Sc3+ content, magnetocrystalline anisotropy of the film changes from uniaxial-type for to conical-type. • With increasing Sc3+ content, magnetic domains change from a mixture of dots and maze structure to more maze-like structure. • The conical magnetic structure transition temperature (T cone) increases with the Sc3+ content until x ≥ 2.1. [ABSTRACT FROM AUTHOR]

In this paper, the ferrimagnetic mixed-spin (3/2, 5/2) Ising model was established to investigate the magnetic and thermodynamic properties of a nanoisland bilayer system with graphene-like structure by Monte Carlo simulation. We have analyzed the magnetization of the system and two sublattices, susceptibility, internal energy and hysteresis loops in detail. We have obtained the phase diagrams of the blocking temperature T B affected by the effects of various physical parameters. The triple hysteresis behavior has been observed, which originates from the competition among various physical parameters. Our results are comparable with those of other theoretical and experimental research. • The ferrimagnetic mixed-spin (3/2, 5/2) graphene-like nanoisland bilayer in the longitudinal magnetic field has been investigated. • Magnetization, susceptibility and internal energy have been discussed. • The phase diagrams of blocking temperature have been obtained under the influence of various physical parameters. • The triple hysteresis behavior have been found for certain physical parameters. [ABSTRACT FROM AUTHOR]

Abstract Exchange bias behaviors up to room temperature have been observed in NiCo 2 O 4 /NiO nanoparticle system. The field-cooled magnetic hysteresis loops exhibit shifts both in the field and magnetization axes simultaneously. The variation of exchange bias field and magnetization shift depends strongly on the measuring temperature. In addition, the dependence of exchange bias effect on measuring temperature is not monotonous, which is reflected in the different tendency during the decrease process of magnetization shift and exchange bias field. The exchange bias field is decreased firstly at the range of 10–50 K followed by an increase of 50–200 K and decreased again of 200–320 K. By analyzing various magnetic measurements, the special exchange bias effect in NiCo 2 O 4 /NiO can be owing to the spin glass state and the ferrimagnetic/antiferromagnetic coupling during different temperature ranges. [ABSTRACT FROM AUTHOR]

Highlights • The magnetic and thermodynamic properties of a ferrimagnetic bilayer superlattice are studied by Monte Carlo simulation. • The phase diagrams in different parameter planes were obtained. • Various types of magnetization curves are observed, depending on physical parameters and temperature. • The triple and double hysteresis loop behaviors exist for certain values of physical parameters. Abstract Monte Carlo simulation has been used to study the magnetic and thermodynamic properties of a ferrimagnetic mixed spin-1 and spin-3/2 Ising bilayer superlattice system on the honeycomb structure. The ground state phase diagrams of the system have been obtained for different single-ion anisotropies and exchange couplings. The system exhibits characteristic critical behaviors such as compensation points, the first- and second-order phase transition points as well as the tricritical points. The effects of the single-ion anisotropies and the exchange couplings on the magnetization, the susceptibility, the internal energy, the specific heat and the hysteresis loops are discussed in detail. Lots of interesting magnetic phenomena have been found, originating from the competitions among the anisotropies, the exchange couplings, the temperature and the external magnetic field. In particular, multiple cycle hysteresis loops behaviors such as the double and triple hysteresis loops have been discovered. Our results are in excellent agreement with previous theoretical studies. [ABSTRACT FROM AUTHOR]

We studied the compensation behavior, the reentrant phenomena characterizing first order phase transitions, and the exchange bias effect manifested by asymmetric hysteresis loops for a core–shell nanotube with mixed spin (1 , 3 / 2) by combining both the effective field theory and the probability distribution technique. Since our system is intended to be disordered on the shell, a uniform distribution for the exchange anisotropy proposed. Among the interesting results are the compensation behavior in the ideal and disordered cases, where we noticed a critical behavior manifested by total magnetization persistence, the compensation behavior accompanied by the reentrant phenomena, as well as the multi-loops behavior, exchange bias effect, and magnetic susceptibility. Internal energy, Helmholtz free energy, and double peak specific heat are also used to invoke the energetic aspect. • Ferrimagnetic systems' magnetic properties. • Disordered magnetic systems. • Reentrant magnetic phenomena. • Multi-hysteresis loops and hysteresis loops. • First order phase transition and compensation temperature. [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]

Compensation temperature T comp and transition temperature T C have significant applications for the experimental realization of magnetic nanotube structure in the field of thermal magnetic recording. In this work, we use the Monte Carlo simulation to investigate the phase diagrams, magnetizations, susceptibilities, internal energies, specific heats and hysteresis behaviors of a cylindrical ferrimagnetic nanotube with core-shell structure. The effects of the single-ion anisotropies ( D C , D S ) and the exchange couplings ( J int , J S ) on the magnetic and thermodynamic properties of the system are examined. A number of characteristic behaviors are discovered in the thermal variations, depending on different physical parameters. In particular, the triple hysteresis loops behavior has been found for appropriate physical parameters. These findings are qualitatively in good agreement with related experimental and the other theoretical results. [ABSTRACT FROM AUTHOR]

Magnetic properties of mixed spin (3/2, 1, 1/2) ferro-ferrimagnetic ternary alloys of the type A y ( B x C 1 − x ) 1 − y are investigated, by means of the Monte Carlo simulation. For this purpose, the influence of concentration, temperature and an external magnetic field on magnetization, magnetic hysteresis loop, magnetic susceptibility and specific heat of ternary alloys with amorphous structures are examined. We found that the compensation temperature exists for some concentrations. Also, it is observed that these ferrimagnetic ternary alloys indicate double hysteresis loop which have been seen theoretically and experimentally in different magnetic alloys. The thermal behavior of magnetization, hysteresis loop and specific heat are also investigated. [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]

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]

• Rare earth doped spinel ferrites were reviewed. • The focus was on hysteresis loop properties. • Literature results were shown by figure and in a tabular form. The development of magnetic materials for modern technology has become a prominent research area due to the rapid growth of modern civilization. Spinel ferrites (ferrimagnetic materials) have good magnetic, structural, optical, electrical, and dielectric properties that make them suitable for potential applications in modern devices. For this reason, the development of ferrites is a big challenge for material researchers. Nowadays, researchers are very much familiar with using rare earth materials as a doping element for the enhancement of the magnetic properties of a ferrite. Rare earth (RE) ions have the ability to tailor the magnetic properties of a ferrite. In this review, we mention how RE ions influence the magnetic hysteresis loop properties of a ferrite. To get an overview, we listed the chemical composition, RE ratio (x), preparation method, annealing temperature (T S), crystallite size (D), saturation magnetization (M S), remanent magnetization (M r), coercive force (H C), squareness ratio (SQR), magnetic moment (n B), and anisotropy constant (K) of the ferrites in a table. We also represent the properties of the M−H loop with figure and try to summarize the doping effect of RE ions in spinel ferrites. This review article has covered a number of significant RE doped spinel ferrites issues that will aid researchers in their future work on this vital topic for the development of magnetic materials and applications. [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]

• Controlled doping of Sn at Sb in full-Heusler Mn 2 NiSb was done. • All the samples were crystallized in Hg 2 CuTi prototype structure as evidenced in refinement. • Interaction between ferromagnetic Mn 2 NiSb and ferrimagnetic Mn 2 NiSb was revealed in ZFC and FC measurements. • Stoner type ferromagnetism was observed in all sample. Alignment of spin of Mn-Mn atoms in Heusler structure mainly depends upon the distance between them which can be easily manipulated by substituting the main group Z-elements in the Mn 2 -based full-Heusler alloys. In this article, we report the effect of Sn doping at the Sb site in the Mn 2 NiSb 1−X Sn X (0.02 ≤ x ≤ 0.1) full-Heusler alloys. We have performed the X-Ray diffraction (XRD) measurement of each sample to obtain the structural information of the synthesized full-Heusler phase. Rietveld refinement performed on the each XRD data of Mn 2 NiSb 1−X Sn X (0.02 ≤ x ≤ 0.1) revealed that all the samples were crystallized in the Hg 2 CuTi prototype (Space group-Fm3m) structure. Analysis of selected area diffraction (SAED) pattern obtained from transmission electron microscopy (TEM) measurement revealed that a single phase of full-Heusler was obtained for the highest Sn content (x = 0.1) sample. Magnetization variation with applied magnetic field plot exhibited the ferromagnetic ground state of each sample as evidenced from hysteresis loop and saturation was obtained up to 1.0 Tesla field. Zero field cooled (ZFC) and field cooled (FC) measurements were also investigated and splitting between ZFC and FC were found to be increasing with an increase in the Sn content. This increment in ZFC and FC splitting with Sn content was attributed to the coupling between the ferrimagnetic (FIM) nature of Mn 2 NiSn phase with ferromagnetic (FM) nature of Mn 2 NiSb phase at the interfaces. Small shifting of hysteresis curve observed in the virgin M-H loop around the origin also indicated the spontaneous exchange biasing due to the FM/FIM interaction. Compensation of magnetization followed by exchange biasing with two magnetic phase (FM/FIM) governed by the controlled doping of Sn in Mn 2 NiSb have been alluringly elaborated. Direct interaction between different known magnetic phases/sub-lattices are rarely investigated which can be used to make suitable materials for spintronic application such as magneto resistive read heads and sensors. [ABSTRACT FROM AUTHOR]

• Magnetic properties of Mn 2 Ru x Ga are sensitive to film strain. • Annealing causes a loss of perpendicular anisotropy by removing strain inducing defects. • Additional valence electrons from diffusion can overcome strain related effects. • Hf and Mo have limited solubility in Mn2RuxGa, makes them suitable as dusting layers. • Intermixing between Co and Pt in a multilayer destroys perpendicular anisotropy. • A CoPt 3 alloy with (220) texture retains this anisotropy after annealing. Perpendicular heterostructures based on a ferrimagnetic Mn 2 Ru x Ga (MRG) layer and a ferromagnetic Co/Pt multilayer were examined to understand the effects of different spacer layers (V, Mo, Hf, HfO x and TiN) on the interfaces with the magnetic electrodes, after annealing at 350 ∘ C. Loss of perpendicular anisotropy in MRG is strongly correlated with a reduction in the substrate-induced tetragonality due to relaxation of the crystal structure. In the absence of diffusion, strain and chemical ordering within MRG are correlated. The limited solubility of both Hf and Mo in MRG is a source of additional valence electrons, which results in an increase in compensation temperature T comp. This also stabilises perpendicular anisotropy, compensating for changes in strain and defect density. The reduction in squareness of the MRG hysteresis loop measured by anomalous Hall effect is <10%, making it useful in active devices. Furthermore, a CoPt 3 phase with (220) texture in the perpendicular Co/Pt free layer promoted by a Mo spacer layer is the only one that retains its perpendicular anisotropy on annealing. [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]

Monte Carlo simulation has been employed to investigate the magnetic properties and phase diagrams of ferrimagnetic mixed-spin (1 / 2 , 1) triangular Ising nanotube with core–shell structure. In particular, the effect of the exchange couplings and the temperature on the magnetic and thermodynamic properties, hysteresis loops, and the compensation temperature have been discussed in detail. Moreover, the effects of the single-ion anisotropy and external magnetic field have been examined. The threshold values of the exchange couplings and single-ion anisotropy have been found, determining whether the system exhibits a compensation temperature. We have found that the appearance of the compensation temperature is strongly linked with the system parameters. Moreover, we have obtained the double and triple hysteresis loops for certain physical parameters in the magnetic system. [ABSTRACT FROM AUTHOR]

In this paper, we have examined in detail the behavior of magnetic properties, hysteresis loops, and compensation phenomenon of a ferrimagnetic mixed spin- (3 ∕ 2 , 2) hexagonal Ising nanowire with alternate layers within the Monte Carlo method based on the Metropolis algorithm. The effect of longitudinal crystal field and exchange coupling constants on the total and the sublattice magnetizations, susceptibilities, specific heat, internal energy, as well as hysteresis loops are investigated for particular parameters. The obtained résults showed different interesting magnetic phenomena, such as seven and triple hysteresis loops at low temperatures, and one or double compensation temperatures under certain parameter values. Our outcomes are also compared with various experimental and theoretical studies. • A hexagonal mixed spin-3/2 and spin-2 Ising ferrimagnetic nanowire with alternate layers, within Monte Carlo simulation techniques. • The effects of the longitudinal crystal fields, the exchange coupling constant, and the temperature on the thermodynamic and magnetic properties and the hysteresis loops were examined in detail. • The seven and triple hysteresis loops at low temperatures, and double compensation temperatures under certain physical parameters. [ABSTRACT FROM AUTHOR]

We applied Monte Carlo simulation to investigate the thermodynamic properties and hysteresis loops of the hexagonal core-shell nanoparticle described by a ferrimagnetic mixed-spin (3/2, 5/2) Ising model. The results revealed the significance of the single-ion anisotropy, exchange coupling, external magnetic field in dominating various thermodynamic quantities and hysteresis loops. We obtained the variation of the critical temperature with various parameters. Under certain parameter conditions, the system may exhibit rich multiple-loop hysteresis behaviors, depending on the competition among the physical parameters. An Ising model of nanoparticle with hexagonal core-shell structure is proposed. The multiple profiles and saturation values of the magnetization are discovered in the system. [Display omitted] • A ferrimagnetic hexagonal core-shell nanoparticle was proposed under an external magnetic field. • Magnetization, susceptibility, and internal energy were discussed by Monte Carlo simulation. • The compensation temperature was found under the effect of single-ion anisotropy. • Multiple-loop hysteresis behaviors were discovered due to the competition among different physical parameters. [ABSTRACT FROM AUTHOR]

• The graphene-like quantum dots with mixed-spin (3/2, 5/2) have been investigated. • The magnetic and thermodynamic behaviors have been explored. • The turnover phenomenon has been found. • The triple-loop behavior has been observed. Based on the Monte Carlo simulation, we have investigated the magnetic and thermodynamic behaviors of the graphene-like quantum dots described by a ferrimagnetic mixed-spin (3/2, 5/2) Ising model. The curves of the magnetization, magnetic susceptibility, internal energy and the specific heat as a function of temperature have been given under various physical parameters. The interesting turnover phenomenon has been found owing to the competition between the crystal field and temperature. It is found that the value of the blocking temperature increases with decreasing the crystal field or increasing the exchange coupling and external magnetic field. We have also investigated the hysteresis loops and found the impossibility of the triple-loop hysteresis behavior for certain parameters. The area of the hysteresis loops can be improved by increasing the exchange coupling and decreasing the absolute values of the crystal field and temperature. [ABSTRACT FROM AUTHOR]

• A three-walled mixed-spin (½, 1, ½) nanotube is constructed. • Different magnetic properties for ferromagnetic and ferrimagnetic cases are established. • Temperature, exchange couplings, and anisotropy have a strong effect on the magnetization plateaus and the multiple-loop hysteresis cycles. • Original behaviors are revealed. The effective field theory with correlations has been employed to study the hysteresis behavior of a ferromagnetic and ferrimagnetic three-walled mixed-spin Ising nanotube with an inner hexagonal vacancy. The effects of different exchange couplings, single-ion anisotropies, and temperature on the hysteresis loops of the sublattices and the overall system are attentively discussed. Multiple hysteresis loops have been observed in the system under certain physical hamiltonian parameters. It is found that the remanences and the coercivity of the sublattices and the system are strongly affected by the temperature, the exchange couplings, and the anisotropy. A satisfactory agreement can be qualitatively achieved by comparing our results with experiments and theoretical studies. Amazing behaviors are revealed thanks to the geometry, the different spins, and the multiple interactions involved in the system. [ABSTRACT FROM AUTHOR]

NiCr 2 O 4 nanoparticles have been successfully prepared by chemical co-precipitation method. Desired crystallographic phase of NiCr 2 O 4 is confirmed by analyzing x-ray diffractrograms. With increasing annealing temperature, crystal transition from cubic to tetragonal phase is observed. The increasing average particle size from ∼80 to ∼280 nm is studied by SEM and TEM micrographs as annealing temperature increases. Exchange bias behavior is detected at 10 K accompanied by the shift of magnetic hysteresis loops along field axis. This effect is gradually weakening as annealing temperature increases. The magnetization depending on temperature under zero-field-cooled and field-cooled conditions suggests the ferrimagnetic transition at ∼72 K and the spiral magnetic order at ∼25 K. Furthermore, the ferrimagnetic transition point shifts slightly to low temperature with increasing annealing temperature. Based on the measurement results, the appearance and evolution of exchange bias effect in NiCr 2 O 4 nanoparticles with improving annealing temperature should be simultaneously derived from the lattice transition and the surface spin effects. • Annealing temperature evidently affects the microstructure and magnetism of NiCr 2 O 4 nanoparticles. • Increasing annealing temperature results in crystal transition from cubic to tetragonal phase. • Increasing average particle size from ∼80 to ∼280 nm is observed as annealing temperature increases. • Magnetic behavior is regulated by crystal transition and particle size due to annealing temperature. [ABSTRACT FROM AUTHOR]

• A ferrimagnetic double-layer core–shell Ising graphene nanoisland was studied in an oscillating magnetic field. • The dynamic order parameter, the susceptibility and the internal energy were discussed by Monte Carlo simulation. • The phase diagrams as well as the multiple-loop hysteresis behaviors were exhibited. • The behaviors of the coercivity and remanence under the influence of various parameters were investigated. By using Monte Carlo simulations, we discuss the dynamic magnetic properties of a double-layer core–shell graphene nanoisland with mixed-spin (2, 5/2) configuration in an oscillating magnetic field. We investigate the influence of exchange couplings, oscillating magnetic field, and temperature on the dynamic magnetic and thermodynamic properties of the system. We obtain the various characteristic curves of the dynamic order parameter, susceptibility, and internal energy as well as hysteresis loops. To better understand the impact of these physical parameters on the phase transition of the system, the phase diagrams are depicted. It should be noticed that the system can exhibit multiple-loop hysteresis behaviors under certain conditions. Besides, we plot the coercivity and remanence of the system under the influence of various parameters. [ABSTRACT FROM AUTHOR]

• The path probability method is applied the mixed spin (1/2, 1) model. • Dynamic magnetic hysteresis loop (DMHL) features of the system are studied. • Effects of interactions parameters on the DMHL features are examined. • Behaviors of coercive fields and remanents magnetizations as the function of angular frequency are investigated. Dynamic magnetic hysteresis loops (DMHL) features of molecular-based magnetic materials and ferrimagnetic systems are investigated by a mixed spin (1/2, 1) model by means of the path probability method (PPM). The PPM contains two rate constants; hence the DMHL features have been studied by using the method with two rate constants. In particular, the effects of the repulsive (J < 0) and attractive (J > 0) bilinear nearest-neighbor pair interactions, temperature (T), crystal-field interaction (D), angular frequency (ω) of the oscillating magnetic field and especially the rate constant (k 2) , which corresponds to the wheel speed in the melt spinning technique (MST), on the DMHL are investigated. The shapes and areas of hysteresis loops are affective sensibility by these system parameters. We also investigate the magnetic coercive fields and remanents magnetizations as a function ω. We found that the most of our results are in a good agreement with some theoretical and experimental reported works. We also observe the novel and interesting DMHL behaviors for lower values of T , and higher values of ω , k 2 and D. [ABSTRACT FROM AUTHOR]

• A new synthesis technique is used to prepare Pb(Zr,Ti)O 3 /CoFe 2 O 4 nanocomposites. • The new low-cost technique maximizes interfacial coupling between the two phases. • The samples are characterized using X-ray diffraction and electron microscopy. • The samples exhibit simultaneous MvsH and PvsE hysteresis loops at room temperature. In the present work, we report the preparation of multiferroic PbZr 0.52 Ti 0.48 O 3 (PZT)/CoFe 2 O 4 (CFO) nanocomposites using a new synthesis technique that can maximize the surface area of contact, and hence, the interfacial coupling between the ferroelectric (PZT) and ferrimagnetic (CFO) phases. The samples have been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the physical (magnetic and dielectric) properties have been investigated. XRD confirms the presence of the desired PZT and CFO phases in the samples without any undesired secondary phases. We also observe a reduction in the particle size of CFO in the nanocomposites as evidenced by a line broadening of the XRD reflections corresponding to the pure CFO phase. The nanocomposites show hysteresis loops and ferrimagnetic-like behaviors in their M vs H curves at room temperature, even for samples with very low fraction of the CFO phase. The coercivity of the nanocomposites is marginally larger compared to that of pure CFO, which can be due to the change in magnetic anisotropy of the CFO phase due to its reduced particle size in the nanocomposites. Room temperature polarization versus electric field measurements show a significant increase in the coercive field after the incorporation of CFO inside the PZT matrix. This work illustrates a simple, cost-effective synthesis technique that can be used to prepare nanocomposites of functional materials with desired room temperature functionalities and enhanced interfacial coupling between the two phases. [ABSTRACT FROM AUTHOR]

• Monte Carlo simulation has been performed to study the magnetocaloric properties of Sr 2 CrIrO 6. • Magnetic entropy change, adiabatic temperature change and relative cooling power have been calculated. • The hysteresis loops of the system are examined as a function of the model parameters. The hysteresis behavior and the magnetocaloric properties of the double perovskite (DP) S r 2 C r I r O 6 near the first and second-order phase transitions have been studied using the Monte Carlo simulations based on the heath bath algorithm. We have investigated the magnetic behavior of the system as a function of the temperature. The amplitude of the total susceptibility and the specific heat peaks increase by increasing the values of the magnetic field h. The magnetic entropy change Δ S m , the adiabatic temperature change Δ T a d are obtained for different external magnetic fields and temperatures. It is found that the system exhibits an inverse magnetocaloric effect when we have a ferrimagnetic interaction between the two sublattices. The relative cooling power (RCP) increases with increasing the external magnetic field and decreases with the temperature. The hysteresis loops of the system are examined as a function of the Hamiltonian parameters the result obtained show that the system may display various hysteresis behaviors such triple, double, single loop and step-like loops. [ABSTRACT FROM AUTHOR]

• Exchange bias in antiferromagnetic/ferrimagnetic layered system. • Magnetic compensation state for ferrimagnetic Gd-Co layer. • Sharp increase and inversion of the sign of exchange bias field for Gd-Co layer. The exchange bias effect in FeNi/FeMn/Gd x Co 100-x films with a pinning antiferromagnetic FeMn layer and an exchange-biased ferrimagnetic amorphous Gd-Co layer was studied. The FeNi layer allows the formation of the fcc lattice of FeMn, i.e. the antiferromagnetic γ-phase of FeMn. The Gd content was varied within 15–25 at. % in order to obtain different temperature dependences of the spontaneous magnetization M s (T) of the Gd-Co layer. The magnetic properties of the films were determined from hysteresis loops measured in the temperature range 5–350 K. A correlation between M s (T) and the temperature dependences of the exchange bias field H ebGdCo (T) was established. In particular, it was shown that there is an inversion of the sign and sharp increase of the value of H ebGdCo near the magnetic compensation state. The first one is a consequence of the minimization of the spontaneous magnetization of Gd-Co layer at the compensation temperature. The second one shows the predominance of the exchange interaction of the antiferromagnetic layer with the cobalt magnetic sub-system of the ferrimagnetic layer as a contribution to the interlayer exchange coupling. [ABSTRACT FROM AUTHOR]

• (Zn,Ni)2Y-type hexaferrites are prepared by modified citric-acid self-combustion. • The temperature is measured of helicoidal-to-ferrimagnetic spin-order transition. • The magnetic properties show complex behavior expressed in triple hysteresis loops. • The magnetic field-induced transitions depend on the degree of nickel substitution. We consider the influence of the magnetic cation (Ni2+) substitution on the structural and magnetic properties of Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 (x = 0.8, 1, 1.5) powders. The powders were synthesized by using the citric-acid sol–gel auto-combustion method. Their ac -magnetization was measured in an ac -magnetic field with an amplitude of 10 Oe and a frequency of 1000 Hz to detect any magnetic phase transitions. A strong influence of the Ni-substitution on the magnetic properties was thus observed. A magnetic phase transition from a helicoidal to a ferrimagnetic spin order at 284 K was observed for the sample Ba 0.5 Sr 1.5 Zn 0.5 Ni 1.5 Fe 12 O 22. The magnetic-phase transition from conical spin order to hellicoidal spin order was registered at 149 K and 177 K for x = 0.8 and x = 1, respectively. Triple hysteresis loops were observed for all samples at 4.2 K, which indicates the presence of two kinds of ferromagnetic states with different magnetization values. [ABSTRACT FROM AUTHOR]

The nonequilibrium magnetic properties (phase transition temperatures, phase diagrams, hysteresis loop areas and correlations) are investigated in the kinetic mixed spin (1/2, 1) Ising nanowire system under the time varying magnetic field. The Glauber-type stochastic dynamics are employed to construct the set of mean field dynamic equations. The time variation of the core/shell magnetizations and the thermal behavior of the dynamic core/shell magnetizations are examined, extensively. The dynamic core/shell magnetizations, hysteresis loop areas and correlations are studied as a function of temperature in order to characterize the nature (continuous or discontinuous) of the phase transitions as well as to find the dynamic phase transition temperatures. The dynamic phase diagrams are presented in the magnetic field amplitude and temperature plane. The dynamic phase diagrams exhibit paramagnetic (p), ferrimagnetic (i), nonmagnetic (nm) phases, three mixed regions, (i + nm), (i + p) and (nm + p). The dynamic phase diagrams contain a dynamic tricritical point and reentrant phenomena, which strongly depend on interaction parameters. • Nonequilibrium magnetic properties of Ising nanowire are investigated. • The Glauber-type stochastic dynamics are employed to construct the set of mean field dynamic equations. • The dynamic phase diagrams are presented in the magnetic field amplitude and temperature plane. • The dynamic phase diagrams contain a dynamic tricritical point and reentrant phenomena. [ABSTRACT FROM AUTHOR]

In this study, we report a facile in situ synthesis of hierarchical NiO/NiFe 2 O 4 sub-microcubes by annealing Ni 3 [Fe(CN) 6 2 sub-microcubes fabricated via a one-step solution-precipitation method. The temperature-dependent magnetization curves show that there exists a collective freezing of the moments of interface spin clusters at T B ≈ 296 K , which further indicates the appearance a coupling interaction between the ferrimagnetic NiFe 2 O 4 and antiferromagnetic NiO nanoparticles. Furthermore, hysteresis loops measurements reveal the existence of an exchange bias effect in the NiO/NiFe 2 O 4 composite system. Interestingly, no training effect of exchange bias is observed, which indicates that the magnetic pinning interaction between NiFe 2 O 4 and NiO is stable and robust. Exchange bias field shows an exponential dependence on temperature and vanishes at about 150 K, which reveals the strong coupling interaction does not improve effectively the thermal stability of exchange bias effect in the current system. The scanning electron microscope (SEM) image of as-synthesized NiO/NiFe 2 O 4 sub-microcubes and hysteresis loops (M − H) under zero-field-cooled (ZFC) and field-cooled (FC) modes measured with a magnetic field of 1 kOe between ± 50 kOe at 2 K. The inset is the central part of M − H loops showing an obvious shift of FC-loop along field axis. Image 1 • NiO/NiFe 2 O 4 sub-microcubes are synthesized by annealing Ni–Fe PBA sub-microcubes. • NiO/NiFe 2 O 4 sub-microcubes exhibit an exchange bias effect. • Exchange bias field shows an exponential dependence on the temperature. • No training effect of exchange bias is observed in NiO/NiFe 2 O 4 sub-microcubes. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a ferrimagnetic mixed-spin (1, 3/2) Ising model to describe the ladder-like graphene nanoribbon. Using the Monte Carlo simulation, the effects of the anisotropies, exchange couplings, longitudinal magnetic field and temperature on the magnetic and thermodynamic properties were investigated. Typical temperature dependences of thermodynamics quantities such as magnetization, susceptibility and internal energy were presented under the influence of various physical parameters. The phase diagrams of blocking temperature were obtained in the different parameter planes. In particular, we also found some interesting double hysteresis loops behavior for certain physical parameters. Our results are consistent with those obtained by some theoretical and experimental researches. • The ferrimagnetic mixed-spin (1, 3/2) Ising ladder-like graphene nanoribbon in the longitudinal magnetic field has been studied. • Magnetization, susceptibility and internal energy have been discussed. • The phase diagrams of the blocking temperature under the influence of different parameters have been obtained. • The double hysteresis loops behavior has been found for certain physical parameters. [ABSTRACT FROM AUTHOR]

We report the annealing-induced exchange bias in Fe–Cu–Pt based heterostructures with Cu as an intermediate layer (Fe/Cu/Pt heterostructure) and as a capping layer (Fe/Pt/Cu heterostructure). The exchange bias (shift in the hysteresis loop along the field axis) observed at room temperature (300 K) is found to be dependent on the annealing temperature. We obtained positive exchange bias of ∼ +120 Oe on annealing both the heterostructures at 400 °C, while on annealing these heterostructures at 500 and 600 °C a negative exchange bias of ∼ −100 Oe was observed. X-ray and polarized neutron reflectivity measurements show the evolution of the depth-dependent structure and magnetic properties of the heterostructures on annealing at different temperatures and revealed the coexistence of soft and hard (alloy) magnetic phases across the thickness of the films. Rapid and long-range interdiffusion at interfaces on annealing the systems at a temperature 〉 400 °C resulted into the formation of a ternary alloy phase. The observation of annealing-induced positive and negative exchange bias effect is dependent on the applied field and majority of the magnetic phase (hard/soft), present in the system. This annealing dependent coupling could give rise to more advanced applications of hard/soft ferromagnetic heterostructures. • Interface exchange interaction at the interface of hard/soft magnetic phases due to annealing. • Coexistence of soft and hard (alloy) magnetic phases across the thickness of the films. • Positive and negative exchange bias at different annealing temperature. • Rapid, long-range interdiffusion and ternary alloy formation at interfaces on annealing 〉 400 °C. [ABSTRACT FROM AUTHOR]

• We study the magnetic and hysteretic properties of Graphene-Based Janus Materials using Monte Carlo calculations and mean field theory. • We show the effects of the number and the positions of dopants on thermodynamic quantities. • We give the conditions for the occurrence of compensation temperature. • We describe the influence of the system's parameters on the hysteresis curves. Based on our works [1–4] , we report the magnetic and hysteretic properties of graphene-based Janus materials namely, pure and doped zigzag graphone nanoribbons, hexagonal core/shell graphene-like nanoribbon, and graphyne core/shell nanoparticle, within the framework of both Monte Carlo calculations and mean field theory. We have reported the effects of the Hamiltonian parameters on the magnetic and the thermodynamic quantities of the systems. The total magnetization, the susceptibility, the specific heat, and the hysteresis curves, as well as the critical temperature and the compensation behavior, that is of crucial importance for technological applications such as thermo-optical recording, are studied. A number of characteristic behaviors are found, such as the existence of two new and non-classified magnetization profiles in addition to the Q -, P -, and N -types of compensation behavior and the occurrence of square, single, and triple hysteresis loops which exhibit different step effects and various shapes. [ABSTRACT FROM AUTHOR]

In this work, we have investigated a ferrimagnetic mixed-spin (2, 5/2) Ising nanoisland with bilayer graphene-like structure within the framework of Monte Carlo simulation. The unique magnetic and thermodynamic behaviors of the system have been revealed under the effects of the Hamiltonian parameters and temperature. We obtain the phase diagrams of the blocking temperatures and discontinuous points. For certain parameters, there are rich multiple-cycle hysteresis behaviors, which is caused by competition among various Hamiltonian parameters. Some results obtained can be compared with other theoretical and experimental studies. • A ferrimagnetic mixed-spin (2, 5/2) graphene-like Ising bilayer nanoisland is proposed. • The magnetization, the susceptibility and the internal energy are studied by Monte Carlo simulation. • Effects of next-nearest-neighbor and next-next-nearest-neighbor intralayer exchange couplings are investigated. • The phase diagrams of the blocking temperatures and discontinuous points in different parameter planes are obtained. • Multiple-cycle hysteresis loops behaviors are discovered for certain values of physical parameters. [ABSTRACT FROM AUTHOR]

• We show enhanced spin transport in MgFe 2 O 4 thin films deposited on Si(100). • The spin current is thermally generated via the spin Seebeck effect (SSE). • Competing FM-AFM interactions manifest as a loop shift in standard hysteresis loops. • A distribution of anisotropy energies for the AFM could explain the results. We observe an exchange bias at low temperatures in polycrystalline ferrimagnetic MgFe 2 O 4 (MFO) films grown on Si(100), emerging from Antiferromagnetic (AFM)-like interactions at defect sites, concentrated predominantly at the grain boundaries. In this report, we show it is possible to utilize these AFM interactions to get enhanced spin transport utilizing the spin Seebeck effect (SSE). The temperature dependence of the SSE signal in two films with different defect densities allowed us to identify a unique temperature window for both films where an enhanced SSE signal was observed. Such enhancement has been reported in different Ferromagnet (FM)/AFM bilayer systems, but its observation in a single layer hosting both FM-AFM interactions makes our results attractive. Temperature dependent SQUID magnetometry revealed two distinct regions of strong and weak coupling for the FM-AFM interactions. The weak coupling region is characterized by a distribution of AFM energy barriers (Δ E), which can modify the spin conductance across the FM-AFM boundary and hence, affect the spin transport. Indeed, we find that the same functional form fits both the Δ E distribution and the SSE temperature evolution for both films. This study should aid in the understanding of SSE in the large class of polycrystalline materials with inherent growth induced defect densities and illustrate the significance of magnetically disordered phases in spin transport. [ABSTRACT FROM AUTHOR]

The Monte Carlo simulation has been applied to study the magnetic behaviors of a ferrimagnetic mixed-spin (1, 2, 5/2) Ising nanoisland with bilayer hexagonal core-shell structure in an external longitudinal magnetic field. We have investigated the influences of the anisotropies, the exchange couplings, the longitudinal field and temperature on magnetization, susceptibility, internal energy and hysteresis loop of the present nanoisland. The behavior of the X parameter (the magnetization, susceptibility, internal energy and blocking temperature) as a function of the parameter is studied. Particularly, the multiple hysteresis loop behaviors have been discovered, such as triple, quintuple, septuple, ninefold and elevenfold hysteresis loops under certain physical parameters. • A ferrimagnetic mixed-spin (1, 2, 5/2) Ising nanoisland with bilayer hexagonal core-shell structure is proposed. • The magnetization, the susceptibility and the internal energy are studied by Monte Carlo simulation. • The phase diagrams of the blocking temperature in different parameter planes are obtained. • The multiple hysteresis loop behaviors are found for certain values of physical parameters. [ABSTRACT FROM AUTHOR]

Using the Monte Carlo method, we have studied the effect of the Hamiltonian parameters (the exchange couplings, the crystal and the magnetic fields) on the magnetizations, the phase diagrams and the hysteresis behavior of a hexagonal ferromagnetic or ferrimagnetic Ising core/shell nanoparticle with mixed spin-5/2 and spin-2. Interesting phenomena have been shown. In particular, the system exhibits the first order transition, the compensation temperature and the compensation crystal field. In addition, the nanoparticle presents single, double, triple and quintuple hysteresis loops. • MCS has been used to study the magnetic properties of a mixed spin-(5/2, 2) Ising core/shell nanoparticle. • The system presents a special point at which four first order transition lines are linked. • The compensation behavior and multiple hysteresis loops have been observed. [ABSTRACT FROM AUTHOR]