Dynamic Magnetic Properties Research Articles

Magnetic behaviour of a mixed-spin ising model on a two-dimensional square-octagon lattice in a dynamic magnetic field

The magnetic behaviours of a two-dimensional square-octagon lattice with mixed spin 5/2 and spin 1 magnetic atoms are investigated in a dynamic magnetic field using effective field theory with correlations. We studied the effects of exchange coupling, anisotropy, oscillating magnetic fields, and temperature on the dynamic magnetic and thermodynamic properties of the square-octagon lattice. The dynamic magnetisation, order parameters, susceptibility, internal energy, and phase diagram of the system were obtained. These results significantly contribute to our understanding of the dynamic magnetic properties of two-dimensional materials. The ability to manipulate and control magnetic behaviour in two dimensions holds promise for the creation of more efficient and versatile devices.

Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet.

The magnetic type-II Weyl semimetal (MWSM) Co3Sn2S2 has recently been found to host a variety of remarkable phenomena including surface Fermi-arcs, giant anomalous Hall effect, and negative flat band magnetism. However, the dynamic magnetic properties remain relatively unexplored. Here, we investigate the ultrafast spin dynamics of Co3Sn2S2 crystal using time-resolved magneto-optical Kerr effect and reflectivity spectroscopies. We observe a transient magnetization behavior, consisting of spin-flipping dominated fast demagnetization, slow demagnetization due to overall half-metallic electronic structures, and an unexpected ultrafast magnetization enhancement lasting hundreds of picoseconds upon femtosecond laser excitation. By combining temperature-, pump fluence-, and pump polarization-dependent measurements, we unambiguously demonstrate the correlation between the ultrafast magnetization enhancement and the Weyl nodes. Our theoretical modelling suggests that the excited electrons are spin-polarized when relaxing, leading to the enhanced spin-up density of states near the Fermi level and the consequently unusual magnetization enhancement. Our results reveal the unique role of the Weyl properties of Co3Sn2S2 in femtosecond laser-induced spin dynamics.

Ligand‐field effect to harness the magnetic anisotropy in a series of mixed valence Co (III)–Co (II) dinuclear complexes

Three mixed valence dinuclear Co (III)–Co (II)‐based complexes having general formulae of [CoIICoIII (HL2)2(L1)] [L1H = 2‐hydroxy‐1‐naphthaldehyde (1), o‐vanillin (2), and salicylaldehyde (3)] have been synthesized successfully using Schiff base (LH4) ligand. The complexes were characterized by single‐crystal XRD, powder XRD, IR, and UV–Vis analyses. The CoII ion with elongated octahedral geometry conferred significant magnetic anisotropy with D values being 64.0(8), 71.1(7), and 52.1(3) cm−1 for 1, 2, and 3, respectively. These complexes exhibited single‐molecule magnet behavior with magnetic relaxation occurring mainly through Raman for 1 and 3 whereas direct and Raman for complex 2. The analysis of the static and dynamic magnetic properties was further supported by theoretical calculations using CASSCF/DLPNO‐NEVPT2.

Effects of whole wheat flour on frozen dough and steamed bread during freeze-thaw cycles

The research on Chinese steamed bread (CSB) with whole wheat flour (WWF) is limited and has not been discussed during freeze-thaw. This study investigated the effects of WWF addition on the dough and CSB quality during freeze-thaw cycles. The results of low-field nuclear magnetic resonance (LF-NMR) and dynamic rheological properties demonstrated that the WWF reduced the adverse changes of freeze-thaw treatment on the dough. Characteristics, texture, and cross section analysis of CSB showed that WWF (20%) could relatively maximize stability. To study the mechanism, arabinoxylan (AX) and water-extractable arabinoxylan (WEAX) from WWF were added to dough. Consistent with WWF, it was found that they could improve freeze-thaw tolerance of frozen dough and CSB. Meanwhile, WEAX (1.12%) could better increase quality and freeze-thaw tolerance of CSB. The results presented in the study indicate that the anti-freeze-thaw effects of WWF could be attributed to AX and WEAX.

Effect of growth rate on structural, magnetic and spin dynamic properties of Co2FeAl thin films

The growth of high-quality Heusler alloy thin films with low damping is essential for designing low-power spintronic devices. Here, we report a systematic investigation of the structural, magnetic, and spin dynamic properties of Co-based (Cobalt, Iron, Aluminum) Heusler alloy Co2FeAl thin films via growth rate variation in sputtering. We found close stoichiometry comparable with the sputtering target towards higher growth rates. However, the stoichiometry of the films is off from the target at relatively low growth rates. The change in stoichiometry can be understood from the variation in the sputtering yield of each element present in the alloy. Grazing incidence X-ray diffraction patterns show that the films with different compositions have the A2 structure. However, the crystallite size strongly depends on the composition. Magneto-optic Kerr effect hysteresis measurements show low coercivity for all the samples, indicating soft magnetic behavior. Spin dynamics study using ferromagnetic resonance reveals that the film with close stoichiometry with the target exhibits the lowest damping parameter, i.e., 0.00448. Our results demonstrate the importance of sputtering growth rate on the structural, elemental, and magnetic properties of Heusler alloy thin films for spintronic device applications.

Magnetic Domain Wall Networked Films – Configurational Switching for Tunable Magnetization Dynamics by Perforated Thin Films

AbstractSetting the magnetization and its properties in magnetic materials and films is of the utmost fundamental and technological importance for magnetic applications and devices. Magnetic permeabilities in a material are generally defined by the acting magnetic anisotropies together with an applied magnetic field. Here, deterministic switching of the effective dynamic magnetic properties is demonstrated by tunable networks of magnetic domain walls. By perforating magnetic films, a reversible switching between different magnetization states is achieved. Due to the resulting local effective dynamic fields for the changed domain configurations, different zero‐field permeability spectra are attained for the same material structure. Using local configurational magnetic resonances confined by magnetic domain walls, deterministic switchable bimodal dynamic behavior is achieved. Dynamic magnetooptical Kerr microscopy with picosecond temporal resolution proves that the varying periodic magnetic domain configurations are responsible for the dynamic magnetic bistability. In particular, the field‐free precessional magnetic response can be reproducibly switched between 1.3 and 2.3 GHz. The magnetization dynamics can be modified by small interventions in a repeatable manner beyond fixed material and structural properties. The described fundamental mechanism enables to design new energy efficient configurational microwave devices by switching between zero‐field magnetic arrangements.

Mechanical and dynamical stability, electronic, magnetic, and thermoelectric properties of RbBaX (X=Si and Ge) half-Heusler compounds

This research paper explores the structural, electronic, magnetic, elastic, dynamic, and thermoelectric properties of sp-based half-Heusler (HH) RbBaX ([Formula: see text] and Ge) compounds using density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) method within the WIEN2k software package. We evaluate the exchange correlation potential using two different approaches: The generalized gradient approximation (GGA) and the modified Becke–Johnson approach. We observe that RbBaX ([Formula: see text] and Ge) adopts a ferromagnetic configuration based on the analysis of total energy against volume. We establish that these alloys possess a genuine half-metallic character because of the full spin polarization observed at the Fermi level in their electronic spectrum. Both compounds under investigation have a total magnetic moment of 1.00[Formula: see text][Formula: see text]B, in agreement with the Slater–Pauling principle. The Born stability criteria for cubic structures and phonon dispersion patterns confirm the mechanical and dynamic stability of RbBaX ([Formula: see text] and Ge) alloys. The thermoelectric properties reveal a p-type semiconductor nature, characterized by significant positive Seebeck values. The thermoelectric figure of merit (ZT) calculated for both alloys at 300[Formula: see text]K approaches unity, highlighting their remarkable thermoelectric efficiency.

Magnetic collective state formation upon tuning the interparticle interactions in ensembles of ultrafine ferrihydrite nanoparticles

The results of a study of the dynamic (alternating current magnetic susceptibility) and static magnetic properties, as well as 57Fe Mössbauer spectrometry and ferromagnetic resonance of two-line ferrihydrite nanoparticle systems with varying intensities of magnetic interparticle interactions are reported. The strength of the magnetic interparticle interactions has been tuned by coating (with various degrees of coating) the ferrihydrite particles (2–4 nm in size and an average size ∼2.7 nm) of the initial synthetic sample by arabinogalactan. Also, a biogenic ferrihydrite sample (an average particle size of 2-nm) with a natural organic coating was studied and it has the weakest magnetic interparticle interactions among of all the samples. Relaxation times of the particle’s magnetic moment were determined by the data of static and dynamic magnetic susceptibilities and from analysis of 57Fe Mössbauer spectrometry. Based on the temperature dependences of the relaxation times, it has been concluded that the predominantly collective processes of freezing of the particle magnetic moments occur under the action of the magnetic interparticle interactions. It is shown that an important role in these processes is played by a magnetic subsystem of the surface spins of the particles. The effect of the interplay between the surface spin and magnetic moment subsystems on the static magnetic properties (low-temperature magnetic hysteresis loops) and the parameters of the microwave absorption line under the magnetic resonance conditions is discussed.

Effects of weak intramolecular interactions and distortions from trigonal prismatic coordination on the magnetic properties of zero-field Co(ii) single-ion magnets

The change of counter anions significantly affects the environment around Co(ii) ions, leading to two zero-field single-ion magnets possessing different uniaxial anisotropies and dynamic magnetic properties.

Augmented magnetic nanoparticle assimilation in rGO sheets for tailored static and dynamic magnetic properties in surface functionalized Co0.8Zn0.2Fe2O4 nanoferrite–rGO hybrid structures

This study focuses on the spin dynamics of magnetic rGO nanocomposites, revealing how optimized nanoparticle dispersion influences the spin relaxation time, spin concentration, and magnetic resonance, crucial for advanced magnetic applications.

Non-equilibrium magnetic properties of a mixed spin (1/2, 1) Ising graphene nanoisland.

Based on Glauber-type stochastic dynamics intertwined with mean field theory, we have investigated a graphene nanoisland's out-of-equilibrium magnetic and thermomagnetic behaviors with a mixed ferrimagnetic spin (1/2, 1) configuration in the presence of an oscillating magnetic field. The influence of the oscillating external magnetic field, single-ion anisotropy and temperature on the dynamic magnetic properties (dynamic phase transitions, hysteresis loop areas, correlations, and phase diagrams) of the system is studied in detail. The results illustrate that single ion anisotropy and the magnetic field play important roles in the system's dynamic order parameters, phase transitions and phase diagrams. Dynamic phase diagrams display some dynamic special points such as dynamic tricritical points, quadruple points and some sort of reentrant phenomena, which strongly depend on interaction parameters. Our predicted results may provide a reference for future experimental and theoretical studies of the nanostructures.

The effect of co-ligands on the performance of single-molecule magnet behaviours in a family of linear trinuclear Zn-Dy-Zn complexes with a compartmental Schiff base.

We present herein magneto-structural studies of three heterometallic Zn2Dy complexes: [Zn2Dy(L)2Cl2(H2O)](ClO4)·4H2O (1), [Zn2Dy(L)2Br2(H2O)](ClO4)·4H2O (2) and [Zn2Dy(L)2(OAc)I(H2O)]I3·4H2O (3), utilizing a new Schiff base ligand, N,N'-bis(3-methoxy-5-methylsalicylidene)-1,2-diaminocyclohexane (H2L). Complexes 1 and 2 exhibit remarkable magnetic relaxation behaviour with relatively high energy barriers in zero field (Ueff: 244 K for 1 and 211 K for 2) and notable hysteresis temperatures, despite the low local geometric symmetry around the central DyIII ions. The SMM performance of these complexes is further enhanced under an applied magnetic field, with Ueff increasing to 309 K for 1 and 269 K for 2, positioning them as elite members within the Zn-Dy SMM family. These findings emphasize the substantial influence of remote modulation on ZnII beyond the first coordination sphere of DyIII ions on their dynamic magnetic relaxation properties. Ab initio studies demonstrate that the relative orientation of the phenoxo-oxygen donor atoms around the DyIII ion is critical for determining the magnetic anisotropy and relaxation dynamics in these systems. Additionally, experimental and theoretical investigations reveal that the coordination of the bridging acetate towards the hard plane, combined with significant distortion from the ideal ZnO2Dy diamond core arrangement caused by the acetate ion, results in low magnetic anisotropy in complex 3, thereby leading to field-induced SMM behaviour. Overall, this study unveils the effects of co-ligands on the SMM performance in a series of linear trinuclear Zn-Dy-Zn complexes, which exhibit low local geometric symmetry around the DyIII centres.

Photoluminescence and magnetic properties of isostructural europium(III), gadolinium(III) and terbium(III) oxamate-based coordination polymers.

Developing and investigating advanced multifunctional materials with magnetic properties as candidates for assembling spin qubits for quantum computing is imperative. A new polytopic ligand based on oxamate and aniline was used to promote the synthesis of three neutral homometallic lanthanide-coordinated polymers. New complexes with the formula {Ln(phox)3(DMSO)2(H2O)}n, where Ln = Eu3+ (1), Gd3+ (2), and Tb3+ (3) [phox = N-(phenyl)oxamate and DMSO = dimethylsulfoxide], were synthesized and well characterized by spectroscopic methods as well as X-ray crystallographic analysis. All crystalline structures comprise neutral zigzag chains. The lanthanide ions are linked by three phox ligands, in which two oxygen atoms from two different ligands are responsible for connecting the trivalent lanthanide ions, and one phox ligand completes the coordination sphere in a bis-bidentate mode, together with two DMSO molecules and one water coordination molecule. The coordination sphere of lanthanide ions consisted of spherical capped square antiprism (CSAPR-9) symmetry. The magnetic properties of 1-3 were investigated in the 2-300 K temperature range. The dynamic (ac) magnetic properties of 2 reveal a frequency dependence involving the phonon bottleneck mechanism below 33 K under nonzero applied dc magnetic fields, resulting in an example of a field-induced single-molecule magnet. Solid-state photophysical measurements for Eu3+ (1) and Tb3+ (3) complexes indicate that the N-(phenyl)oxamate ligands are very efficient in sensitizing the lanthanide(III) ions in the visible region of the electromagnetic spectrum. Compounds 1 and 3 exhibited an emission in the red and green regions, respectively. Experimental results and theoretical calculations using the Sparkle/RM1 method support a quantum efficiency of ∼72% for 1, suggesting its potential as a candidate for light conversion molecular devices (LCMDs).

Largely enhanced compressive strength and plastic deformation of Fe-doped all-d-metal heusler alloy Cr2CoV

The structure dynamic stability, magnetic property, strength, and plastic deformation of all-d-metal Heusler alloys Cr2Co1-xFexV (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) have been investigated in this study. It is found that Cr2Co1-xFexV alloys tend to crystalize in the XA-type Heusler phase. The atomic radius becomes the decisive factor in determining the lattice size. With the increase of Fe concentration, the interaction between Cr(B)-Fe atoms increases, resulting in the increase of Curie temperature. The magnetic moments of the Cr2CoV and Cr2FeV are analyzed in conjunction with the theoretical calculations. The ductility and compressive strength of the materials gradually increase with the increase of Fe content. Especially in Cr2FeV alloy, a high compressive strength of up to 3050 MPa and a large ductility of up to 61% are achieved, and no fracture occurs, showing excellent mechanical properties. The electron localization function diagram shows that d-d orbital hybridization is formed and weak in Cr2CoV and Cr2FeV alloys, which helps to form metal bonds. Consequently, the ductility of the all-d-metal Heusler alloys was improved, which increased the fatigue life in practical application.

Static and dynamic magnetic properties of circular and square cobalt nanodots in hexagonal cells.

In this work we performed a detailed numerical analysis to investigate the static and dynamic magnetic properties of hexagonal cells of square and circular cobalt nanodots as a function of the distance between them and the external magnetic field to which they are subjected. By simulating hysteresis curves with the external magnetic field applied parallel and perpendicular to the plane of these nanostructures, we can conclude that the cobalt nanodots presented a significant perpendicular magnetic anisotropy. We also obtained that the coercivity increases with decreasing volume, which implies that the circular dots have a higher coercivity than the square dots. Furthermore, we studied the dynamic susceptibility of these systems and found that it is possible to control both the position and the number of resonance peaks by controlling the geometry and the distance between the magnetic nanodots. This work provides useful information on the behaviour of cobalt nanodot arrays, opening paths for the design and improvement of two-dimensional technological devices.

Collective behavior in arrays of coupled ferromagnetic magneto-dipole

The analytical model of ellipsoid chains (ECh) has been used in several works to describe magnetic (static and dynamic) properties. In the present work the model validity was tested, applied to hexagonal arrays of Ni ECh by means of Prolate ellipsoids with transversal diameter of 30 nm and longitudinal dimensions of 60 nm. Two different chains were tested, one formed by 1 ellipsoid and the other formed by 6 ellipsoids. Two inter-chains distances were tested to analyze the strong dipole interaction effects in the arrays. Hexagonal arrays of 100 chains (constituted by 1 and 6 ellipsoids) were analyzed with the inter-chain distance of 45 nm and 60 nm. The dimensions were chosen motivated by the experimental results reported in literature in ferromagnetic nanowires deposited in porous alumina membranes. The ferromagnetic resonance results were generated by means of micromagnetic simulation through the Nmag package. A standard problem was executed, in which the magnetization deviated from the equilibrium direction and, through the temporal dependence, the main frequency was determined by means of a Fast Fourier Transformation. The simulation results were analyzed and fitted by using the analytical model based on ellipsoids (with uniaxial anisotropy). The effective field of magnetic anisotropy was obtained from the fitting of the above analytical model with the calculated data. From the results, even with ellipsoids in such small sizes (close to the one domain configuration for Ni particles), the model in which the magnetization is assumed to be homogeneous is not completely valid. The best correspondence was in the limiting case of longer inter-chain distances. This shows the limitations of the analytical model, often used in systems with very close particles.

Impact of Twin's Landscape on the Magnetic Damping of La2/3Sr1/3MnO3 Thin Films

AbstractUnderstanding the origin and mechanisms of magnetic damping in complex oxide materials is crucial for optimizing spin dynamics and tailoring their properties for specific spintronic applications. Ferromagnetic resonance spectroscopy (FMR) technique has been used to investigate the magnetic damping of multiple La2/3Sr1/3MnO3 (LSMO) epitaxial thin films with similar thickness and identical DC magnetic properties. However, the dynamic magnetic properties exhibit noticeable variations among samples. Microstructural analyses using X‐ray diffraction (XRD) and atomic force microscopy (AFM), confirm that the samples are structurally identical, except for minute differences in the miscut angles of the substrates. Nevertheless, when examining the samples using backscattered electron (BSE) images in scanning electron microscopy (SEM), significant disparities in the twin distribution are observed. These variations in the twin distribution directly correlate with the observed differences in the damping values. A careful image analysis of BSE images allows to demonstrate that the increase of damping is due to the pinning of the magnetization in the twin boundaries.

Static and dynamic magnetization control of extrinsic multiferroics by the converse magneto-photostrictive effect

Using strain to control magnetic properties through anisotropy changes is a method to create functional materials with energy efficient applications. The strain can be inferred remotely by the light-induced non-thermal dimension change of materials named the photostrictive effect. Still, the control of dynamic magnetic properties via this effect is pursued. The need of a physical quantity to encompass and to describe anisotropic magnetization changes under the photostrictive effect is also remaining. Here, the photostrictive effect with visible light is used to engineer static and dynamic magnetic properties in a multiferroic material. A converse magneto-photostrictive coupling coefficient is also proposed as a physical quantity to assess anisotropic magnetization changes under this effect. These results provide a path towards understanding light-induced magnetization changes and a potential to be used in wireless approaches for the control of magnetic properties and tunable RF/microwave devices.

Magnetization properties, super-stable points, and cycles of antiferromagnetic spin-1 diamond chains with nodal-nodal interactions

This study is devoted to the discovery of super-stable points and cycles in antiferromagnetic Ising and Ising-Heisenberg models with spin 1 on diamond chains with nodal-nodal interactions. These phenomena are important for understanding the complex behavior of magnetic systems. We specifically investigate their connection with magnetization plateaus, which serve as critical indicators of the model’s characteristics. Employing the recurrence relations technique, we derive multidimensional rational mappings that give insights about the statistical properties of the models. Carefully examining the stability properties of these mappings, in particular, by analyzing the maximum Lyapunov exponent, we have revealed the complex relationship between the magnetization plateau and dynamic properties. Throughout our extensive research, we have comprehensively studied the existence and behavior of super-stable points and cycles for various parameter configurations in spin-1 models on the diamond chains. By highlighting the basic properties of dynamics and stability, our research advances a fundamental understanding of complex magnetic systems and their fascinating properties.

Regulation of static and dynamic magnetic properties of amorphous FeCoZr composition gradient films by Zr doping

A series of amorphous FeCoZr composition gradient monolayer films with varying Zr contents was prepared on the Si(100) substrate using RF magnetron sputtering. The effects of the Zr sputtering power PZr on the static and dynamic magnetic properties of FeCoZr films were systematically investigated. The results demonstrate that the introduction of the Zr element as a composition gradient into FeCo films not only improves the soft magnetic properties of the films but also enhances their in-plane uniaxial magnetic anisotropy. In particular, the doping of Zr elements leads to the destruction of FeCo lattice, inducing a transformation of the films from polycrystalline to amorphous state, resulting in a significant decrease in coercivity (Hc reduced by 82%) and surface roughness (Ra reduced by 78%). In addition, as PZr increases from 30 to 70 W, the anisotropy fields Hk of the films increase from 128 to 340 Oe, and the resonance frequency fr increases from 4.24 to 5.23 GHz. By fitting the permeability spectrum using the LLG equation, it is found that FeCoZr composition gradient films exhibit a lower damping coefficient α of around 0.011–0.014, indicating the reduction of energy loss during magnetization dynamics. These findings highlight the potential applications of FeCoZr composition gradient films in the field of high-frequency microwaves.