Ferrimagnetic Coupling Research Articles

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.

Layer-Dependent Quantum Anomalous Hall and Quantum Spin Hall Effects in Two-Dimensional LiFeTe.

The emergence of an intrinsic quantum anomalous Hall (QAH) insulator with long-range magnetic order triggers unprecedented prosperity for combining topology and magnetism in low dimensions. Here, based on stacked two-dimensional LiFeTe, we confirm that magnetic coupling and topological electronic states can be simultaneously manipulated by just changing the layer numbers. Monolayer LiFeTe shows intralayer ferrimagnetic coupling, behaving as a QAH insulator with Chern number C = 2. Beyond the monolayer, the odd and even layers of LiFeTe correspond to uncompensated and compensated interlayer antiferromagnets, resulting in unexpected QAH and quantum spin Hall (QSH) states, respectively. Moreover, the spin Chern number is proportional to the stacking layer numbers in even-layer LiFeTe, proving that the spin Hall conductivity can be continuously enhanced by increasing layer numbers. Therefore, the odd-even-layer-dependent QAH and QSH effects found in LiFeTe topological insulators offer new insight into regulating quantum states in two-dimensional topological materials.

New insights on the Jacobsite mineral from Bahia and related synthetic manganese-ferrite nanoparticles.

Jacobsite is a relatively rare mineral of composition MnFe2O4, found in Urandi (Bahia State) in Brazil. It is also a common species in the deep-sea manganese nodules, attracting the interest of many mineral-extracting companies. Because of its spinel constitution similar to magnetite, Jacobsite is commonly called a manganese-ferrite. However, the manganese/iron content may vary substantially according to its origin, demanding specific studies in each case. The Jacobsite mineral inspired our laboratory synthesis of the analogous manganese ferrite nanoparticles. The direct synthesis by the coprecipitation method has not been successful; however, it can be carried in the presence of citrate ions, yielding strongly magnetic nanoparticles, with a maximum magnetization of 45.6 emu.g1. Although they were structurally identical to Jacobsite, the mineral from Bahia exhibited a rather weak magnetism, because it involves a ferrimagnetic coupling. For this reason, the synthetic method seems to provide a better way of obtaining strongly magnetic manganese ferrites. These magnetic nanoparticles have been investigated in detail, including their interaction with diatoms, providing interesting magnetic bio-silicate carriers in drug delivery.

CaCu3Mn2Te2O12: An Intrinsic Ferrimagnetic Insulator Prepared Under High Pressure.

CaCu3Mn2Te2O12 was synthesized using high-temperature and high-pressure conditions. The compound possesses an A- and B site ordered quadruple perovskite structure in Pn3̅ symmetry with the charge combination of CaCu32+Mn22+Te26+O12. A ferrimagnetic phase transition originating from the antiferromagnetic interaction between A' site Cu2+ and B site Mn2+ ions is found to occur at TC ≈ 100 K. CaCu3Mn2Te2O12 also shows insulating electric conductivity. Optical measurement demonstrates the energy bandgap to be about 1.9 eV, in agreement with the high B site degree of chemical order between Mn2+ and Te6+. The first-principles theoretical calculations confirm the Cu2+(↓)-Mn2+(↑) ferrimagnetic coupling as well as the insulating nature with an up-spin direct bandgap. The current CaCu3Mn2Te2O12 provides an intriguing example of an intrinsic ferrimagnetic insulator with promising applications in advanced spintronic devices.

Magnetic properties as a function of temperature of La and Gd co-doped YIG nanoparticles

This paper presents the behavior of saturation magnetization and other magnetic properties depending on the temperature variation from the nanoparticles of YIG doped and co-doped with Gd and La at different concentrations. The samples were prepared according to the sol–gel method, resulting in crystallite sizes ranging from 55 nm to 121.2 nm. X-ray diffraction measurements and microscopy show details of the structural characterization of the compounds. The magnetization values were measured as a function of the external magnetic field of up to 20 kOe at temperatures between 2K and 300K. The saturation magnetization varied between 25.23 emu/g and 29.10 emu/g, at 300K. At 2K, the variation occurs between 30.72 emu/g and 39.92 emu/g. The magnetic properties of compound, are high sensitivity to temperature variations and the results showed a weakened ferrimagnetic coupling with the dopant concentration. Also, changes in the cubic anisotropy constant with temperature were verified.

Trilayer graphene-like structure under defect with ferrimagnetic interlayer coupling

Trilayer graphene-like structure under defect with ferrimagnetic interlayer coupling

Evolution of phase structure and magnetic property with Mn content and heat treatment in Fe3-xMnxGa alloy

The evolution of structure and magnetic property with Mn content and different heat- treatment in Fe3-xMnxGa alloy has been investigated in this study. First-principles calculations suggest that the small energy difference between the different structures of Fe3Ga and Fe2MnGa alloys leads to the instability of them. The phase transformation for samples being quenched from 623 K, 883 K, 1073 K and the ribbons are studied with X-ray diffraction. Body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal structures are observed and the schematic phase diagram is given in this paper. Together with the theoretical calculation moments for Fe3Ga and Fe2MnGa with different crystal structures and magnetic configurations, the magnetic properties are discussed. The saturation magnetization MS of bcc and hexagonal Fe3-xMnxGa samples at 5 K gradually decreases with increasing Mn content, which can be attributed to the increase of the fraction of Fe-Mn antiferromagnetic (AFM) coupling. In fcc Fe2MnGa, with the increase of quenching temperature from 623 K to 1073 K, more ferrimagnetic (FIM) coupling phase with higher energy is formed, showing a decrease of MS and unsaturation of magnetization under the test magnetic field in MH curve. A magnetic field induced AFM to FIM state transition is found in Fe2MnGa alloy with L12 type of atomic disorder when quenched from 1073 K. The tunable structure and magnetic properties make it has the potential applications in versatile material field.

Half-metallic ferromagnetism in new quaternary Heusler alloys CoX’YP (X’ = Cr and Fe)

ABSTRACT In this study, we investigated the structural, electronic and magnetic properties of new quaternary Heusler alloys CoX'YP (X’ = Cr and Fe) using the accurate full-potential linearised augmented plane waves with local orbitals (FP-LAPW + lo) under the framework of the density functional theory (DFT) and the WIEN2k package. The generalised gradient approximation (GGA) is chosen to treat the exchange–correlation (XC) energy. The structural properties of the presented alloys are investigated in order to determine their structural parameters at equilibrium, such as: the lattice constant (a0 ), the bulk modulus (B0 ) and its first pressure derivative (B’). The structural stability of the CoCrYP and CoFeYP alloys is found in Y-type (I) structure, while their magnetic stability is reported in ferromagnetic phase. The electronic properties of the studied materials show the complete half-metallic character. The magnetic properties reveal that the total magnetic moment of the two alloys is found in integer value, obeying the Slater-Pauling rule. Furthermore, the calculated local magnetic moments of Co and X’ atoms are found with opposite signs, confirming the ferrimagnetic coupling within these compounds. According to the electronic and magnetic results found in this approach, we conclude that the compounds CoCrYP and CoFeYP are full half-metallic ferromagnetic materials.

Engineering Spin Configurations of Synthetic Antiferromagnet by Controlling Long-Range Oscillatory Interlayer Coupling and Neighboring Ferrimagnetic Coupling.

Controllable manipulation of specific spin configurations of magnetic materials is the key to constructing functional spintronic devices. Here, it is demonstrated by integrating the merits of ferromagnetic, ferrimagnetic, and antiferromagnetic spin configurations into one synthetic antiferromagnetic (SAF) heterostructure by controlling both long-range oscillatory interlayer coupling and neighboring ferrimagnetic coupling. A controllable manipulation of four types of spin configurations of the Pt/[Co/Pt/Co]/Ru/CoTb SAF heterostructures composed of ferromagnetic Co/Pt/Co and ferrimagnetic CoTb layers is successfully achieved. In particular, the compensated magnetization, enhanced anomalous Hall resistance in the remanence state, wide-temperature spin-orbit torque switching of magnetization, and high immunity to the external magnetic field are simultaneously obtained in one of the SAF heterojunctions with macroscopic interlayer antiferromagnetic coupling. This design concept of engineering spin configurations may enable efficient spin manipulation for customized memory and logic applications.

Compensation temperature and dynamic magnetic properties in the double-layer structure of graphyne-like

The physical properties of the double-layer structure of graphyne-like described by the Ising model were studied by effective-field theory with correlations. The system is composed of mixed spin 5/2 and 2 with ferrimagnetic exchange couplings. The magnetization curve of the system can be divided into three types: P-, Q-, and N-types. Multiple compensation temperatures on the magnetization curve were found within a range of parameters. In addition, the influence of a periodically oscillating magnetic field on the magnetization of the double-layer structure of graphyne-like is discussed. The results indicated that the disorder and order of the system could be controlled and induced by a time-dependent and independent magnetic field.

Effect of Fe doping on the magnetic property of perovskite TmCr1-xFexO3

Single-phase samples of TmCr1-xFexO3 (x = 0–1) with the space group Pnma were prepared through solid state reactions and their magnetic properties were investigated. TmCr1-xFexO3 exhibit paramagnetic to canted antiferromagnetic phase transition for × = 0–0.6. Monotonically increased TN is observed with the increasing of doping content x. When × increases from 0 to 0.6, TN increases from 126 K to 343 K. Such change can be attributed to the increased angle of Cr/Fe-O(4c)-Cr/Fe, which stabilizes the noncollinear spin structure of Cr/Fe sublattice and enhances the super-exchange interaction. Magnetization reversal was observed for × = 0–0.3, and the compensation temperature Tcomp increases with the increase of x. This is due to the decrease of internal field HI, which results from a ferrimagnetic coupling between Cr3+ and Fe3+. The exchange bias phenomenon was also observed for × = 0–0.3. However, the exchange bias field HEB decreases with × increasing, a consequence of the weakening of the pinning effect of Cr/Fe3+ moments below Tcomp.

Electronic and Magnetic Properties of Eutectoid Growth Mn-rich Ge1-xMnx Dilute Magnetic Semiconductors

Background: Dilute magnetic semiconductors (DMSs) have attracted great attention in recent years due to their potential applications in spintronic devices. Objective: This study aimed to investigate the magnetic and electronic properties of Mn-rich Ge semiconductors. Methods: The magnetic and electronic properties of eutectoid growth Mn-rich Ge1-xMnx dilute magnetic semiconductors (DMSs) with a high Mn dopant close to the composition of Ge2Mn are investigated by the first-principles calculations. Results: Using the diamond structure models of Ge24Mn8, Ge22Mn10, and Ge20Mn12, we show that the magnetic interactions of Mn atoms are dominated by ferrimagnetic coupling and that the Mn 3d states are substantially hybridized with the valence bands of the Ge matrix. Conclusion: This indicates that Mn-rich Ge1-xMnx DMSs demonstrate a ferromagnetic and metallic character, and their carriers can mobilize in the lattice more freely. The present investigation could provide insights into understanding the nature of transition-metal-rich dilute magnetic semiconductors.

First-principles study of the (001) and (110) surfaces of CrCoIrGa Heusler alloy

Exploring highly spin-polarized thin films of magnetic materials is of great importance for spin-based device applications. Herein, the structure, spin-polarization and magnetic properties of the (001) and (110) surfaces of CrCoIrGa Heusler alloy have been investigated using first-principles density functional theory (DFT) and DFT + U calculations. The results demonstrate that while bulk CrCoIrGa is highly spin-polarized (89%), the surface counterparts exhibit much lower spin-polarization (SP), being due to the emergence of surface states at Fermi level (EF). It is observed that the (001) surface geometries are kept well, whereas, the (110) surface exhibit an obvious surface reconstruction after relaxation, resulting in large surface formation energy. The electronic properties investigated at DFT level revealed that CrGa-terminated (001) surface carries 100% SP, CoIr-terminated has 63% SP, and the (110) surface retains the bulk SP. Interestingly, the SP is found to be suppressed on introducing U parameter in the calculations. All the considered surfaces display ferrimagnetic coupling, with a significant total magnetic moment. In addition, the surface layer atoms carry large SP and moments than the inner layer atoms, and thus promise a dominant role in spin-based device applications of the thin film surfaces.

Saturation magnetization as a function of temperature in Zn doped YIG nanoparticles

The behavior of saturation magnetization as a function of temperature ( M S ( T ) ), in Zinc doped YIG nanoparticles was investigated. The samples, with crystallite size between 40 nm and 78 nm were synthesized by the sol–gel method. With the data obtained through the vibrating sample magnetometry, an adjustment with the Approach law to obtain the saturation magnetization at temperatures between 50 K and 300 K was performed. With the data it was possible to get the M S × T experimental plots. Curves were fitted with the most recent proposal by Cojocaru et al., where an expression for M ( T ) is derived using a three-dimensional generalization of Heisenberg’s Hamiltonian, that take into account geometry, size and boundary conditions of magnetic nanoparticles. A good correspondence was obtained between the experimental data and the adjustment through the proposal. Analyzing the parameters obtained through the fitting, it was possible to visualize a weakening in the ferrimagnetic coupling with increased doping of Zn. It was also possible to see a good adjustment of the proposal with the change in the nanoparticles shape. The proposal proved to be very useful for the study of the nanoparticles. • The Cojocaru’s proposal proved to be a good tool for the study of magnetic nanoparticles. • Capture changes due to the atomic disorder caused by doping. • The type of contour condition in the particles is complex according to the system.

Magnetic and thermodynamic properties of monolayer graphdiyne-like

Magnetic and thermodynamic properties of a monolayer graphdiyne-like described by Ising model were examined by effective-field theory with correlations. Within a range of typical parameters, compensation behavior on the magnetization and two peaks on the susceptibility and specific heat curves have been found with the ferrimagnetic exchange couplings. The effects of the anisotropies on the monolayer graphdiyne-like have been discussed and the phase diagrams have been obtained.

Cation ratio and oxygen defects for engineering the magnetic transition of monodisperse nonstoichiometric zinc ferrite nanoparticles

Monodisperse nonstoichiometric zinc ferrite nanoparticles with a tunable size of 4.1–32.2 nm are fabricated via thermal decomposition. An extrinsic impurity phase of the ZnO component is present in the zinc ferrite nanoparticles with a size of <10 nm, but this phase can be eliminated after the air annealing treatment. The atom ratio of Zn/Fe and concentration of oxygen vacancies decrease as the particle size of zinc ferrite increases, causing magnetic transition from superparamagnetism to ferromagnetism. The X-ray magnetic circular dichroism spectra reveal that the spin magnetic moments of Fe3+ are reduced, and the orbital magnetic moments are frozen with the increasing atom ratio of Zn/Fe. Therefore, saturation magnetization decreases. The saturation magnetizations of all the zinc ferrite nanoparticles decrease after the air annealing treatment, suggesting that oxygen vacancies considerably influence the magnetic properties. The air annealing treatment can minimize the number of oxygen defects, which trigger some of the Fe3+-OV-Fe3+ ferrimagnetic couplings to transfer into the Fe3+-O2−-Fe3+ antiferromagnetic couplings. This work provides new insights regarding the magnetic performance of spinel ferrites by tuning the stoichiometric ratio and oxygen defects.

Investigation of the stability, electronic structure, and magnetic properties of Sc2VZ (Z = Ge, Si) Heusler alloys: First-principles calculations

In this work, the thermodynamical, dynamical, and mechanical stability of the XA-type structure of the Sc2VZ (Z = Ge, Si) were investigated by density functional theory. The calculated electronic properties of these alloys by generalized gradient approximation, revealed the half-metallic characteristic having the bandgap of 0.64 eV and 0.77 eV in the spin-up band of Sc2VGe and Sc2VSi, respectively, whereas the metallic behavior was observed in their spin-down band. The details of the magnetic properties were studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism which showed the ferrimagnetic coupling between the transition metals in these structures.

Effect of surface modification treatment on top-pinned MTJ with perpendicular easy axis

We investigated the effects of surface modification treatment (SMT) on the perpendicular magnetic anisotropy (PMA) and the thermal tolerance of top-pinned magnetic tunnel junctions (MTJs) with a Co/Pt synthetic ferrimagnetic coupling reference layer. Applying an SMT to the bottom Pt layer increased the PMA of the overlying Co/Pt multilayer. X-ray diffraction spectrum analysis revealed that the SMT resulted in a higher crystallinity and smaller lattice spacing in the Co/Pt multilayer in the thinner bottom Pt layer, which may have increased the PMA in the Co/Pt multilayer. The tunnel magnetoresistance (TMR) ratio of the MTJ with SMT increased as the annealing temperature was increased up to 400 °C; conversely, the TMR ratio of the MTJ without SMT decreased at an annealing temperature of 400 °C. Evaluation of the m-H loops revealed that, after annealing at 400 °C, the reference layers in the MTJs after SMT possessed better magnetic properties than those in the MTJs without an SMT; this is attributable to the higher PMA of the reference layers with SMT. EDX line analysis revealed that SMT suppressed Pt diffusion to the MgO barrier, resulting in a higher thermal tolerance and larger PMA of the reference layer.

Novel 'main-part' isostructuralism in metal complexes with 1-methylimidazole: crystal structures, energy calculations and magnetic properties.

Two new transition metal complexes with 1-methylimidazole (1-MeIm) and azide as ligands, namely, [Co(1-MeIm)4(N3)2] (1) and [Ni(1-MeIm)4(N3)2] (2), have been synthesized and characterized by IR, Raman, UV-Vis and XPS spectroscopy. Their crystal structures were solved by single-crystal X-ray diffraction. The supramolecular self-assembly of the two complexes is governed by non-classical C-H⋯N hydrogen bonds and C-H⋯π interactions. Lattice energies and intermolecular interaction energies for various molecular pairs are quantified using the PIXEL method. DFT computational studies to assess the binding energy through modern tools like non-covalent interaction (NCI plots) analysis and reduced density gradient (RDG) analysis have also been carried out. A detailed analysis of geometric descriptors revealed the existence of quasi-isostructural pairs or 'main-part' isostructuralism in a series formed by 1, 2, and a related cadmium complex, being more evident in the 1/2 pair. DFT studies using theoretical models have been used to disclose the relative importance of the H-bond and C-H⋯π noncovalent interactions. Magnetic measurements for compound 1 show weak ferrimagnetic coupling between adjacent M(II) centers, mediated by H-bonding and C-H⋯π non-covalent interactions.

Structural tuning for enhanced magnetic performance by Y substitution in FeB-based metallic glasses

Despite the compositional analogue to Fe71B17(NbYZr)12 metallic glass, the Fe71B17Y12 metallic glass has a saturated magnetization of Ca 108 emu g−1, more than 5 times of that in Fe71B17(NbYZr)12 (20 emu g−1). The structural origin for such significant difference in magnetic performance was investigated by x-ray absorption fine structure spectra and ab initio molecular dynamics (AIMD) simulations including simulated pair-correlation function (PCF) and Voronoi tessellation. Based on the Heisenberg model of magnetism, the narrow distribution of Fe–Fe bonds with larger distances accounts for a large Fe moment of 2.0 μ B in Fe71B17Y12, while the broad distribution of Fe–Fe bonds leads to ferrimagnetic couplings which result in the small net Fe moment of 0.45 μ B in Fe71B17(NbYZr)12. This work emphasizes how the substitution of analogous 4d transition metals induces a significantly different magnetism, which sheds lights on the development of new magnetic metallic glasses with both a promising magnetic performance and larger glass forming ability.