Ferrimagnetic System Research Articles

Dynamic magnetic behaviors and magnetocaloric effect of CrI3-like bilayer structure

Abstract Through the utilization of Monte Carlo simulations, the dynamic magnetic characteristics and magnetocaloric effect of a CrI3-like bilayer structure featuring mixed spin (3/2, 1) are explored. First, a detailed analysis is conducted on the influence of different parameters such as exchange coupling and dynamic magnetic field on the order parameter, susceptibility, and internal energy of the ferrimagnetic system. Various interesting phenomena have been discovered, such as the occurrence of a maximum in the magnetization curve, a double-peak behavior in the magnetic susceptibility curve, and the blocking temperature exhibiting an initial increase followed by a subsequent decrease with the increase of the bias field. During the investigation of hysteresis loops, a multi-loop phenomenon is observed. Various parameters are being examined to evaluate how they affect the magnetic entropy change, adiabatic temperature, and relative cooling power of the ferromagnetic system. These discoveries could prove advantageous when implementing them in spintronic devices and refrigeration technology.

Relaxation dynamics of a mixed ferrimagnetic Ising system with random anisotropy

The relaxation dynamics of a mixed spin-1/2 and spin-1 ferrimagnetic Ising system with random anisotropy has been investigated using Onsager’s theory of irreversible thermodynamics. The magnetic Gibbs energy production, arising due to irreversible processes, is computed using the equilibrium mean-field Gibbs energy, based on the variational principle and the Gibbs–Bogoliubov inequality. In the framework of linear response theory, the time derivatives of the sublattice magnetizations are treated as fluxes conjugate to their corresponding generalized forces. Two relaxation times are computed, and their dependence on temperature and crystal field variances is examined near phase transition points for four distinct topologies, each corresponding to different phase diagrams. These phase diagrams emerge from random anisotropy drawn from a bimodal probability distribution: P(Δi)=12δ(Δi-Δ(1+α))+δ(Δi-Δ(1-α)). One of the relaxation times, denoted as τ1, increases rapidly and diverges near the critical and tricritical points separating the ferrimagnetic and paramagnetic phases. For α≥0, critical slowing down, characterized by the divergence of τ1, is observed near the isolated ordered critical points between the ferrimagnetic and disorder-induced ferrimagnetic phases. Finally, the variance of the relaxation times is analyzed across regions of crystal field and temperature, as well as the values of α at which re-entrant phenomena occur, due to the competing interactions in the random system.

Critical, compensation and hysteresis behaviors studies in the ferrimagnetic Blume-Capel model with mixed half-integer spin-(3/2, 7/2): Exact recursion relations calculations

The exact recursion relations are used to study the mixed half-integer spin-(3/2, 7/2) Blume-Capel Ising ferrimagnetic system on the Bethe lattice. Ground-state phase diagrams are computed in the (DA /q|J|, DB /q|J|) plane to reveal different possible ground states of the model. Using the thermal changes of the order-arameters, interesting temperature dependent phase diagrams are constructed in the (DA/|J|, kT/|J|), (DB/|J|, kT/|J|) planes as well as in the (D/|J|, kT/|J|) plane where D = DA = DB. It is revealed that the system exhibits first- and second-order phase transitions and compensation temperatures for specific model parameter values. Under the constraint of an external magnetic field, the model also produces multi-hysteresis behaviors as single, double and triple hysteresis cycles. Particularly, the impacts of the ferrimagnetic coupling J on the remanent magnetization and the coercitive fields for selected values of the other physical parameters of the system are pointed out. Our numerical results are qualitatively consistent with those reported in the literature.

Spin-wave resonance frequency and quantum fluctuation of the (anti)ferri-(anti)ferrimagnetic double-layer superlattice

The Hamiltonian of a four-sublattice simple cubic superlattice was solved by applying the linear spin-wave theory and the retarded Green's function technique. This study focused on the spin-wave resonance frequency, energy gap, sublattice magnetization, and quantum fluctuations of the system. The results show that the spin quantum number, interlayer (intralayer) exchange couplings, and intralayer anisotropy have a significant influence. In the ground state, the magnetizations of the sublattices are smaller than their spin quantum numbers, indicating the existence of quantum zero-point vibrations in the (anti)ferrimagnetic-(anti)ferrimagnetic bilayer system.

Exploring magnetic behavior and compensation temperatures in spherical and hemispherical lattices: A Monte Carlo study

The magnetic behavior of spherical and hemispherical lattices under various conditions was insufficiently understood prior to this study, particularly about the influence of ferrimagnetic coupling parameters, external magnetic and crystal fields on the compensation and blocking temperatures. In current study Monte Carlo simulations provide new insight into how these factors affect the magnetic properties of spherical and hemispherical lattices, revealing critical size-related effects and dependencies. This study offers key insights into the magnetic properties of spherical and hemispherical lattices, critical for advancing magnetic materials in future nanotechnologies. The ferrimagnetic system studied, hold promise for applications such as MRI, cancer therapy, and next-generation memories, enhancing nanoscale sensor precision and driving progress in data storage and device miniaturization.

A Monte Carlo study of Magnetic and thermodynamic behaviors of L[formula omitted] structure like quadrangular frustum pyramid nanoisland

Based on the Monte Carlo simulation, research has been conducted on the magnetic and thermodynamic behaviors of a ferrimagnetic mixed-spin (5/2, 1/2) L10 nanoisland with a like quadrangular frustum pyramid structure. We studied the effects of the magneto-crystal anisotropy and exchange coupling on the magnetization, susceptibility, internal energy, and hysteresis loops. The ferrimagnetic system exhibits more abundant magnetic and thermodynamic behavior than the cubic L10 nanoisland. We found eight saturation values of magnetization, five-loop hysteresis loops, and abrupt transitions in the low-temperature region. In addition, the exchange coupling effect of ferrimagnetism also promotes magnetic properties. Interestingly, in this system, the ferromagnetic exchange coupling (Jaa) and external magnetic field (h) linearly depend on the blocking temperature TB. The hysteresis loops of the system have more magnetization steps, which reflects that it has more ground state spin configurations.

Enhanced spin pumping in heterostructures of coupled ferrimagnetic garnets

Spin pumping has significant implications for spintronics, providing a mechanism to manipulate and transport spins for information processing. Understanding and harnessing spin currents through spin pumping is critical for the development of efficient spintronic devices. The use of a magnetic insulator with low damping enhances the signal-to-noise ratio in crucial experiments such as spin-torque ferromagnetic resonance (FMR) and spin pumping. A magnetic insulator coupled with a heavy metal or quantum material offers a more straightforward model system, especially when investigating spin-charge interconversion processes to greater accuracy. This simplicity arises from the absence of unwanted effects caused by conduction electrons unlike in ferromagnetic metals. Here, we investigate the spin pumping in coupled ferrimagnetic (FiM) Y3Fe5O12 (YIG)/Tm3Fe5O12 (TmIG) bilayers combined with heavy-metal (Pt) using the inverse spin Hall effect. It is observed that magnon transmission occurs at both of the FiMs FMR positions. The enhancement of spin pumping voltage (Vsp) in the FiM garnet heterostructures is observed. The plausible reason might be the interfacial exchange coupling between FiMs. The modulation of Vsp is achieved by tuning the bilayer structure. Further, the spin mixing conductance for these coupled systems is found to be ≈1018 m−2. Our findings describe a coupled FiM system for the investigation of magnon coupling providing opportunities for magnonic devices.

Non-Hermitian spin dynamics in a coupled ferrimagnetic system

Non-Hermitian spin dynamics in a coupled ferrimagnetic system

Magnetic properties of a ferrimagnetic transverse Ising system on the multilayer kagome-like lattice

Based on the Trotter-Suzuki formula, the transverse Ising model is proposed to investigate the magnetic properties of a ferrimagnetic multilayer kagome-like lattice by Monte Carlo simulation. When different parameters are considered, the rich magnetization profiles and the multi-loop hysteresis behaviors are observed. It is found that there is a small peak in the transverse magnetization curve, which is related to the phase transition temperature.

A new Mn(Ⅱ)-based metal-organic framework: synthesis, characterization, ferrimagnetic behavior and catalytic conversion of CO2 to cyclic carbonates

A new three-dimensional (3D) metal–organic framework (MOF) [Mn3(bqca)2(DMF)4]n (1) is constructed based on a tricarboxylate ligand 2,3-di-(4-carboxyphenyl)-quinoline-6-carboxylic acid (H3bqca) through solvothermal reaction. The structure, composition and stability of the complex were fully characterized by single crystal X-ray diffraction, powder X-ray diffraction, infrared spectrum and thermogravimetric analysis. The results show that 1 has a 3D microporous framework and exhibits high thermal stability up to 450 ℃. Direct-current magnetic susceptibility reveals that 1 is a rare ferrimagnetic homospin system. Importantly, 1 can effectively catalyze the cycloaddition reaction of CO2 with epoxides to generate cyclic carbonates with high yields and selectivity, and it can also be recycled at least five times without a noticeable change in catalytic efficiency.

Chiral Skyrmions Interacting with Chiral Flowers.

The chiral nature of active matter plays an important role in the dynamics of active matter interacting with chiral structures. Skyrmions are chiral objects, and their interactions with chiral nanostructures can lead to intriguing phenomena. Here, we explore the random-walk dynamics of a thermally activated chiral skyrmion interacting with a chiral flower-like obstacle in a ferromagnetic layer, which could create topology-dependent outcomes. It is a spontaneous mesoscopic order-from-disorder phenomenon driven by the thermal fluctuations and topological nature of skyrmions that exists only in ferromagnetic and ferrimagnetic systems. The interactions between the skyrmions and chiral flowers at finite temperatures can be utilized to control the skyrmion position and distribution without applying any external driving force or temperature gradient. The phenomenon that thermally activated skyrmions are dynamically coupled to chiral flowers may provide a new way to design topological sorting devices.

Direct observation of Néel-type skyrmions and domain walls in a ferrimagnetic DyCo3 thin film

Isolated magnetic skyrmions are stable, topologically protected spin textures that are at the forefront of research interests today due to their potential applications in information technology. A distinct class of skyrmion hosts are rare earth - transition metal (RE-TM) ferrimagnetic materials. To date, the nature and the control of basic traits of skyrmions in these materials are not fully understood. We show that for an archetypal ferrimagnetic material DyCo3 that exhibits a strong perpendicular anisotropy, the ferrimagnetic skyrmion size can be tuned by an external magnetic field. Moreover, by taking advantage of the high spatial resolution of scanning transmission X-ray microscopy (STXM) and utilizing a large x-ray magnetic linear dichroism (XMLD) contrast that occurs naturally at the RE resonant edges, we resolve the nature of the magnetic domain walls of ferrimagnetic skyrmions. We demonstrate that through this method one can easily discriminate between Bloch and Néel type domain walls for each individual skyrmion. For all isolated ferrimagnetic skyrmions, we observe that the domain walls are of Néel-type. This key information is corroborated with results of micromagnetic simulations and allows us to conclude on the nature of the Dzyaloshinskii-Moriya interaction (DMI) which concurs to the stabilisation of skyrmions in this ferrimagnetic system. Establishing that an intrinsic DMI occurs in RE-TM materials will also be beneficial towards a deeper understanding of chiral spin texture control in ferrimagnetic materials.

Mixed Spin Ising Ferrimagnetic System in the Oguchi Approximation

It has been investigated an Ising ferrimagnet with mixed spin-2 and spin-5/2 and various crystal field parameters on a body-centered cubic lattice. In this research paper, ferrimagnetic compensation temperatures and phase transitions to clarify the characteristic features, in a series of molecular-based magnets AFeIIFeIII(C2O4)3[A=N(n-CnH2n+1)4, n=3-5] are examined in the Oguchi approximation (OA). The spin crystal domain dependence of compensation behavior acting on ions contain the Oguchi lattice, is mainly studied. It is discovered, specifically, that magnetic anisotropies in the disordered for the two sublattices of the model depend on the negative values of the crystal fields to produce a characteristic ferrimagnetic behavior. For DA/|J|=-1.5 and DB/|J|=-5.5, there are two compensation points are induced at an ordered phase(2,-1.5).

Magnetic properties and hysteresis behavior of a mixed spin-3/2 and spin-3 Ising ferrimagnetic system in a graphene monolayer

Using the mean field approximation (MFA), we have successfully investigated the magnetic properties of the mixed spin Sj=±3,±2,±1,0 and σi=±32,±12 Ising ferrimagnetic system in a graphene layer. The effects of different physical parameters, namely exchange interactions, anisotropies, external field and temperature on the critical, first-order, compensation and hysteresis behaviors have been examined. The results show that, for specific values of these parameters, interesting phenomena appeared, such as compensation and multi-loop hysteresis behavior. It was shown that the compensation phenomenon only occurs if the exchange interaction JA (interaction between spins σi), is greater than a certain minimum value JAmin. We have also shown that, for fixed values of the anisotropies, the relation between JAmin and the exchange interaction JB (interaction between Sj), is a linear one. In addition, we found that each of the behaviors mentioned above is sensitive to the change of a certain physical parameter. Finally, we have verified that our results are comparable with those of other works.

Dynamic magnetic hysteresis features of a mixed spin (2, 5/2) Ising system on a hexagonal lattice under an oscillating magnetic field within the path probability method

Recently, we [J. Magn. Magn. Mater. 514 (2020) 167242] presented a study of the dynamic magnetic loop features of molecular-based magnetic materials and ferrimagnetism that were investigated by using a mixed spin 1/2 and spin-1 ferrimagnetic Ising system within the path probability method. We found several interesting dynamic magnetic hysteresis properties and observed that the obtained results are in qualitatively good agreement with some theoretical and experimental studies in magnetic materials. We extended our recent previous published work to study the dynamic magnetic hysteresis properties of molecular-based magnetic materials and ferrimagnetism utilizing the mixed spin (2, 5/2) ferrimagnetic Ising system on a hexagonal lattice employing the path probability method. The spin (2, 5/2) Ising system is one of the most suitable and most used prototypical systems to investigate many molecular-based magnetic materials and ferrimagnetic materials. We found more interesting dynamic magnetic hysteresis properties such as double, triple, quadruple and quintuple loop behaviors for the layer magnetization, and only double and triple loops for the total magnetization. We found that some of our obtained results are in qualitatively good agreement with some theoretical, experimental reported works, and the works on some magnetic materials as obtained by the melt-spinning technique.

The role of Zn and Ru substitution on the structural, magnetic and dielectric properties of ferrite cuprospinels

A comprehensive study on the structural, magnetic and dielectric behavior of ferrite cuprospinels with site specific substitution of non-magnetic Zn and weakly magnetic Ru ions has been presented. Such substitution leads to two classes of stable crystal symmetries, (i) tetragonal (I41/amd): CuFe1.95Ru0.05O4 and Cu0.95Zn0.05Fe1.95Ru0.05O4 and (ii) cubic (Fd-3m):Cu0.60Zn0.40Fe1.95Ru0.05O4 and Cu0.05Zn0.95Fe1.95Ru0.05O4 bulk polycrystals. The former set of compounds undergo significant Jahn-Teller (JT) distortion due to high Cu content and such distortion gets lifted with the substitution of non-magnetic Zn ions. Ferrimagnetic (FiM) behavior is predominant in all these compounds except the highest Zn (95 at.%) content cubic system with diluted substitution of Ru (2.5 at.%) which exhibits antiferromagnetic ordering below the Néel temperature (T N ∼ 10.9 K). We employed Néel’s expression for FiM systems applicable for the two sublattice model to extract the dominant exchange interactions (J AA , J AB and J BB ) between the A-site and B-site cations. Subsequently the high temperature (300 K T 900 K) inverse paramagnetic susceptibility data has been fitted to the above expression which yields dominant ∼ 391 K with very high asymptotic Curie temperature for the tetragonally distorted dilute Zn substituted cuprospinel, while the Zn-rich cubic system exhibits ∼ 300 K. On the other hand, the tetragonally distorted spinel devoid of Zn exhibits dominant ∼ 229 K with negligible and moderate (65 K) signifying that the JT active ions cause the onset of magnetic frustration and enhanced ordering temperatures. All the investigated systems exhibit significant magneto-crystalline anisotropy with a maximum anisotropy field H K ∼ 6 kOe and maximum anisotropy constant (K 1 ∼ 10.88×105 erg cm−3). The broadband dielectric spectroscopy studies reveal significant enhancement of mid-frequency dielectric constant ε R (f, T) with plateau-like feature over a wide temperature and frequency window, together with low-loss as a result of the incorporation of Ru ions into the tetragonally distorted spinel lattice. The ac resistivity ρ(f, T) studies reveal that the mode of conduction follows Mott’s variable-range hopping (VRH) model with a linear logarithmic variation of ρ ac versus T −0.25. The temperature dependence of the VRH activation energy of charge carriers follows a linear behavior which indicates the presence of localized polaron in all the investigated systems.

Critical and Compensation Behaviors of a Ferrimagnetic Multilayer System

By the use of Monte Carlo simulation, we have investigated the phase diagrams and magnetic properties of a ferrimagnetic Ising multilayer system with mixed spins (1, [Formula: see text]). The ground-state phase diagrams are first constructed for [Formula: see text]. To examine the influences of certain physical parameters of the system, namely the exchange interactions, the number of layers and the crystal field, we have studied the thermal behavior of the system magnetizations and the corresponding phase diagrams. The results obtained in this work show the existence of second- and first-order phase transitions and compensation temperatures. Moreover, we have investigated the hysteresis behavior, where the multi-loop phenomena are observed.

Effects of site dilution on Compensation in Ising Spin-1/2 trilayered triangular Ferrimagnets with non-equivalent planes

Using Monte Carlo simulations with the Metropolis algorithm, the magnetic and thermodynamic behaviours of a spin-1/2, trilayered ferrimagnetic system on triangular monolayers with quenched nonmagnetic impurities are studied. Two different theoretical atoms, A and B, make up the ABA and AAB types of distinct configurations. Like atoms (A-A and B-B) interact ferromagnetically, while unlike atoms (A-B) interact antiferromagnetically. Only the A-layers are randomly site-diluted with dilution percentages ranging from 5% to 45%. Such diluted magnetic thin systems exhibit magnetic compensation which depends sensitively on the concentration of impurities. The phase diagram in the Hamiltonian parameter space related to the occurrence of magnetic compensation phenomenon and the effect of site dilution is discussed in detail. Special attention is given to the mathematical dependencies of compensation temperature on the concentration of nonmagnetic impurities. Depending upon the concentration of nonmagnetic impurities, the compensation and critical points shift with the equilibrium magnetic behaviours changing between distinct ferrimagnetic behaviours. For each combination of the coupling strengths, with values of the impurity concentration above a threshold, compensation appears where previously was absent. Suggested mathematical formulae show how threshold impurity concentration relies on Hamiltonian parameters.

Anomalous impact of thermal fluctuations on spin transfer torque induced ferrimagnetic switching

The dynamics of a spin torque-driven ferrimagnetic (FiM) system is investigated using the two-sublattice macrospin model. We demonstrate ultrafast switching in the picosecond range. However, we find that the excessive current leads to magnetic oscillation. Therefore, faster switching cannot be achieved by unlimitedly increasing the current. By systematically studying the impact of thermal fluctuations, we find that the dynamics of FiMs can also be distinguished into the precessional region, the thermally activated region, and the crossover region. However, in the precessional region, there is a significant deviation between FiM and ferromagnet (FM), i.e., the FM is insensitive to thermal fluctuations since its switching is only determined by the amount of net charge. In contrast, we find that the thermal effect is pronounced even when a very short current pulse is applied to the FiM. We attribute this anomalous effect to the complex relation between the anisotropy and overdrive current. By controlling the magnetic anisotropy, we demonstrate that the FiM can also be configured to be insensitive to thermal fluctuations. This controllable thermal property makes the FiM promising in many emerging applications such as the implementation of tunable activation functions in the neuromorphic computing.

Sublattice Magnetizations of Ultrathin Ferrimagnetic Lamellar Nanostructures between Cobalt Leads

In this work, we model the salient magnetic properties of the alloy lamellar ferrimagnetic nanostructures [Formula: see text] between [Formula: see text] semiinfinite leads. We have employed the Ising spin effective field theory (EFT) to compute the reliable magnetic exchange constants for the pure cobalt [Formula: see text] and gadolinium [Formula: see text] materials in complete agreement with their experimental data. The sublattice magnetizations of the [Formula: see text] and [Formula: see text] sites on the individual hcp atomic (0001) planes of the Co–Gd layered nanostructures are computed for each plane and corresponding sites by using the combined EFT and mean field theory (MFT) spin methods. The sublattice magnetizations, effective site magnetic moments, and ferrimagnetic compensation characteristics for the individual hcp atomic planes of the embedded nanostructures, are computed as a function of temperature, and for various stable eutectic concentrations in the range [Formula: see text]. The theoretical results for the sublattice magnetizations and the local magnetic variables of these ultrathin ferrimagnetic lamellar nanostructured systems, between cobalt leads, are necessary for the study of their magnonic transport properties, and eventually their spintronic dynamic computations. The method developed in this work is general and can be applied to comparable magnetic systems nanostructured with other materials.