Magnetic Crystalline Anisotropy Research Articles

Microstructural, magnetic, and optical properties of nickel-doped spinel zinc ferrite nanoparticles

This study focuses on the synthesis of nickel-substituted zinc ferrite nanoparticles, , via the sol-gel method and examines how nickel substitution influences their structural, magnetic, and optical properties. The lattice constant of the nanoparticles, which varied from 8.4296 Å to 8.4212 Å, decreased as the nickel concentration increased. Scanning electron microscopy (SEM) was employed to examine the morphology, revealing grain sizes between 46 and 53 nm, while energy dispersive X-ray spectroscopy (EDX) confirmed the elemental composition, showing nearly spherical nanoparticles containing all the constituent elements. The magnetic properties were analyzed using a vibrating sample magnetometer (VSM), which highlighted significant differences between the theoretical and experimental magnetic moments, indicating the presence of Yafet-Kittel magnetic ordering in the system. The saturation magnetization was enhanced by ions, reaching a maximum value of 23.864 emu/g. This enhancement makes the nickel-substituted zinc ferrite nanoparticles suitable for applications in data recording media and magnetic resonance imaging. Additionally, the values of the magnetic crystalline anisotropy constant, initial permeability, effective anisotropy constant, and anisotropic field of the synthesized samples were estimated.The optical properties of the synthesized samples were evaluated using UV-visible spectroscopy, and the band gap was determined through diffuse reflectance spectroscopy (DRS). The optical bandgap of pure zinc ferrite was measured to be 2.26 eV, and it decreased with increasing nickel concentration in the nanoparticles.

Elucidation of structural, electromagnetic, and optical properties of Cu–Mg ferrite nanoparticles

Copper doped magnesium ferrite, Mg1-xCuxFe2O4(x = 0.0–1.0) nanomaterials were synthesized via. sol-gel method sintered at 600 °C for 2 h. The synthesized materials were characterized using modern sophisticated techniques viz. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy, Energy dispersive x-ray spectroscopy (EDS), Vibrating sample magnetometer, UV–visible diffuse reflectance spectra and Impedance analyzer. XRD analysis revealed that all the samples were single phase cubic spinel structure with Fd3m space group and investigated the change in structural parameters with copper concentration. The average crystallite size in the range of 11–23 nm and lattice parameters decrease with increasing Cu doping, due to the cationic distribution and ionic radius. The SEM images show the agglomeration of the particles with spherical like shape and elemental percentage were obtained from EDX. The saturation magnetization showed an increasing trend with increasing Cu concentration at a certain level and then decreases due to the rearrangement of cations at tetrahedral and octahedral sites. The Coercivity, Retentivity and magnetic crystalline anisotropy increase with changing dopant concentration. The magnetic measurements showed enhanced saturation magnetization at certain level (28.96emu/gm) and increase in coercivity up to 1102 Oe with changing dopant concentration. The estimated band gap energy is found to increase with Cu content. The dielectric constant, dielectric loss and impedance show normal behavior of ferrite. The frequency dependent dielectric constant decrease and tan delta shows a relaxation behavior at low frequencies. The synthesized nano Mg–Cu nanoparticles will be applied as humidity sensor, gas sensor, microwave devices and photocatalyst.

Study on the relationship between structure and magnetic properties of τ-phase MnAl prepared by cryo-milling

The unique characteristics, such as high magnetic moment, high Curie temperature, large magnetic crystalline anisotropy, and low cost, make the τ-phase MnAl a promising candidate as the market alternatives which could fill the gap between the rare earth magnets and ferrite magnets. Because at low temperatures the metal will become more brittle, the cryomilling technology may allow the τ-phase MnAl to be broken quickly and introduce few crystal defects, and then obtain better permanent magnetic properties. In this study, the cryomilling technology was used to grind the τ-phase MnAl, and the structural and magnetic properties of the obtained powder sample were investigated. It was found that compared to room-temperature ball milling, the morphology of cryomilled powders is granular and the powder agglomeration is dramatically suppressed at a low temperature, and as a result the larger particles tend to be broken down into smaller ones rather than being agglomerated to larger thin layers. The grain size D reduced continuously from 145 nm to 36 nm when the sample was milled for 120 minutes. The coercivity increased with increasing the cryo-milling time, while the saturation magnetization decreased. The maximum coercivity of up to 4.9 kOe was obtained by cryo-milling for 100 minutes. By the neutron diffraction analysis, it was confirmed that the decrease of the saturation magnetization with increasing milling time is mainly due to the migration of Mn atoms from 1a site to the 1d site and the decrease of Mn atomic magnetic moment.

Crystalline Magnetic Anisotropy in High Entropy (Fe, Co, Ni, Cr, Mn)3O4 Oxide Driven by Single‐Element Orbital Anisotropy

AbstractThe design of multicomponent materials has captured considerable attention due to its extraordinary ability to tailor functional properties. However, how a single element affects the behavior of the overall material has yet to be explored in depth. In this study, the heteroepitaxy of high entropy (Fe, Co, Ni, Cr, Mn)3O4 films with varying strain states are investigated in magnetic performance. It is discovered that the high entropy oxide thin film with compressive strain exhibits an effect of crystalline magnetic anisotropy. Diverse analyses provide a detailed understanding of high entropy magnetic oxide systems, including X‐ray diffraction, reciprocal space mapping, macroscopic magnetic characterization, X‐ray absorption spectroscopy (XAS), etc. Notably, the element‐specific XAS technique proves effective in uncovering the origin of the crystalline magnetic anisotropy. Due to the substrate‐induced epitaxial strain, the eg orbitals of Mn3+ form different energy levels, leading to different preferred electron occupancy. The exploration of magnetic properties in epitaxial high entropy oxide film is then raveled. By navigating the complexities introduced by the random atom distribution and intricate magnetic interactions, this study pioneers novel methodologies for probing the core physics of high entropy oxides.

Computational Discovery of High-Temperature Ferromagnetic Semiconductor Monolayer H-MnN2.

In the past few years, two-dimensional (2D) high-temperature ferromagnetic semiconductor (FMS) materials with novelty and excellent properties have attracted much attention due to their potential in spintronics applications. In this work, using first-principles calculations, we predict that the H-MnN2 monolayer with the H-MoS2-type structure is a stable intrinsic FMS with an indirect band gap of 0.79 eV and a high Curie temperature (Tc) of 380 K. The monolayer also has a considerable in-plane magnetic anisotropy energy (IMAE) of 1005.70 μeV/atom, including a magnetic shape anisotropy energy induced by the dipole-dipole interaction (shape-MAE) of 168.37 μeV/atom and a magnetic crystalline anisotropy energy resulting from spin-orbit coupling (SOC-MAE) of 837.33 μeV/atom. Further, based on the second-order perturbation theory, its in-plane SOC-MAE of 837.33 μeV/atom is revealed to mainly derive from the couplings of Mn-dxz,dyz and Mn-dx2-y2,dxy orbitals through Lz in the same spin channel. In addition, the biaxial strain and carrier doping can effectively tune the monolayer's magnetic and electronic properties. Such as, under the hole and few electrons doping, the transition from semiconductor to half-metal can be realized, and its Tc can go up to 520 and 620 K under 5% tensile strain and 0.3 hole doping, respectively. Therefore, our research will provide a new, promising 2D FMS for spintronics devices.

Electronic structure and magnetothermal property of two-dimensional ferromagnetic NbSe2 monolayer regulated by carrier concentration

Investigating high-performance and stable spintronics devices has been a research hotspot in recent years. In this paper, we employed first-principles methods and Monte Carlo (MC) simulations to explore the structure, electronic, and magnetic properties of monolayer NbSe2, as well as its behavior under carrier concentration modulation. The research on the electronic structure reveals that by introducing an appropriate amount of holes, the material can undergo a transition from metal to a half-metal state, achieving 100% high spin polarization. Investigation of magnetic crystalline anisotropy shows that the magnetic crystal anisotropy energy of 1210 μeV in out-of-plane is beneficial to maintain ferromagnetic order at high temperatures. In addition, doping with suitable carriers can effectively enhance or strengthen the ferromagnetic coupling in NbSe2 so that the magnetization easy axis is shifted. This reveals the potential application prospects of NbSe2 in electronically controlled spintronic devices. Analysis of the Fermi surface shows that both holes and electron doping increase the Fermi velocity of the material. The effect of hole doping is particularly significant, indicating its potential application in Fermi velocity engineering. Under the theoretical framework of the extended two-dimensional Ising model, based on MC simulation, the Curie temperature (TC) of NbSe2 is predicted to be 162 K. The effects of carrier concentration and the magnetic field on the magnetic and thermal properties of monolayer NbSe2 are simulated. The results show that appropriately increasing the hole doping concentration and magnetic field is conducive to obtaining ferromagnetic half-metallic materials with TC higher than room temperature, which provides theoretical support for experimental preparation.

(Digital Presentation) Microstructure, Corrosion Resistance, and Magnetic Properties of Amorphous Alloy Co75Si15Fe5Cr4,5Al0,5 before and after Corrosion

Cobalt-based Amorphous Metal Alloys (AMA) can be used as soft magnetic materials in various magnetic devices due to the low value of the natural crystalline magnetic anisotropy. The addition of non-metallic components (Si, B) does not adversely affect the magnetic properties. On the contrary, AMA have high magnetic permeability at low values of coercive force and greater resistance to corrosion compared to crystalline ones.The required important parameters for corrosion description are: the concentration of chloride-ions, the microstructure (especially surface heterogeneity) and the composition of the oxide layer [1]. It was determined that the initial AMA Co75Si15Fe5Cr4.5Al0.5 possesses the low coercive force 0.38 A/m. The modification of the alloy surface with nanostructures by anodizing at different current densities (i) and times in the BmimBF4 ionic liquid (IL) does not affect the value of the coercive force, but its resistance to corrosion in a chloride solution increases. The coercive force increases after corrosion, which may be due to a change in surface morphology.The domain structures of the surface modified with nanostructures and initial alloys are different. After excerption at a constant (i) in IL, the domain structure of the surface consists of relatively large uniformly magnetized regions (Fig. 1a). The coercive force of the sample practically does not change compared to the initial sample.The surface domains after corrosion are broken into smaller ones, while the predominant orientation changes its direction (Fig.1 b). The change in the surface domain structure is accompanied by a significant increase in the coercive force (by a factor of 10), although the maximum magnetic permeability (the slope of the hysteresis loops) does not change.The EIS-tests (electrical impedance spectroscopy) were performed at -200 mV (Ag/AgCl) in the frequency range of 50,000 to 0.01 Hz and an oscillation amplitude of 20 mA in Ringer's solution (Fig.1 c, d) to compare the charge transfer kinetics for modified with nanostructures and initial samples. The simulated equivalent circuit included the values of the solution resistance Rs (22 Ω), the value of the constant phase element CPE associated with the double layer capacity, including the capacitance of the modified surface layer, and Rp is the charge transfer resistance across the interface. The capacity of the double layer is higher for the modified sample (4.28*10-5 Ohm-1*cN vs. 1.88*10-5 Ом-1*сN ) and the resistance value of the material has hardly changed (18000±13.5% Ohm for modified and 15500±3.5% Ohm for unmodified). The values of the phase angle (0.78 - modified and 0.88 - unmodified) indicate a greater heterogeneity of the charge distribution at the boundaries of the double layer for the modified surface of the alloy.So, surface modification affects the corrosion resistance, while it has little effect on the parameters of hysteresis loops, what is very important in practical applications. Nyby, C., Guo, X., Saal, J. E., Chien, S.-C., Gerard, A. Y., Ke, H., Frankel, G. S. (2021). Electrochemical metrics for corrosion resistant alloys. Scientific Data, 8(1).doi:10.1038/s41597-021-00840-y Figure 1

Crystalline electric field and magnetic anisotropy in Dy-based icosahedral quasicrystal and approximant

Crystalline electric field and magnetic anisotropy in Dy-based icosahedral quasicrystal and approximant

Influence of oxygen and nitrogen doping on the structure and magnetic properties of CoNi alloy: First principle calculations

We have studied the effects of oxygen and nitrogen doping as interstitial defects on the structure and magnetic properties of CoNi alloy using the first principle density functional theory, where we include the orbital-spin interaction in the calculations. Our calculations reveal that the CoNi:ONi in the L10-structure has a large enhancement in the saturation magnetization (Ms) and a small reduction in the magnetic crystalline anisotropy (MCA). For CoNi:OCo, we found a small reduction in Ms and MCA. However, for CoNi:NCo and CoNi:NNi there is always a reduction in Ms and MCA. Therefore, the first alloy could be suitable for permanent magnets. A detailed analysis of other parameters, such as the magnetic hardness parameter (κ), optimum supercell parameters, anisotropy field (Ha), and formation energy (Efor) is presented. The interstitial oxygen doping enhances the magnetic properties.

Magnetic anisotropy in two-orbital models

Motivated by the recent first-principle discovery of giant perpendicular magnetic anisotropy (PMA) in Fe/III–V nitride thin films, we theoretically study magnetic crystalline anisotropy(MCA) in a series of lattices with trigonal symmetry. Due to the trigonal crystal field, MCA in these lattices is dominated by first-order perturbation of the spin–orbit coupling (SOC) in the atomic limit, instead of second-order in conventional transition metal materials. In particular, the proportionality between MCA and SOC is robust in Kagome and pyrochlore lattices due to the flat bands therein. While in triangle lattice the second-order relation is restored under the bandwidth effect. These findings give rise to a new understanding of magnetic anisotropy and provide a guide for the future hunting of high PMA materials.

Crystalline orientation-related magnetic anisotropy in transition metal dichalcogenides 1T′-MoTe2/Co heterostructures

The semimetal transition metal dichalcogenides (TMD) MoTe2 have attracted extensive research interests in Spintronics. The understanding of the magnetic properties of MoTe2/Ferromagnetic (FM) heterostructures is critical to the design of novel Spintronics-based devices. However, there is lack of research on the magnetic anisotropy of the semimetal TMD/FM. Here, we demonstrate the in-plane crystalline orientation-related magnetic properties of MoTe2/Co to clarify the relationship between the crystalline orientation and the magnetic anisotropy. We carried out the studies of crystalline orientation-related magnetic anisotropy in 1T′-MoTe2/Co heterostructures from both experiments and first-principles calculations. Our results show that for Co with different thicknesses, the easy axis of Co film is along the b-axis of MoTe2 with uniaxial magnetic anisotropy. It is also consistent with the results of our theoretical results. When Co film thickness increases, the magnetocrystalline anisotropy (MCA) oscillates around a constant value with a lower MCA along the out-of-plane direction. Meanwhile, the demagnetization energy which increases linearly as a function of Co thickness, which would make the easy axis in-plane. Our work may give a fundamental inspiration for Spintronics based devices with semi-metallic TMDs/ferromagnetic materials.

Ferroelectric control of the Néel vector in L10-type antiferromagnetic films

How to efficiently manipulate the N\'eel vector of antiferromagnets (AFM) by electric methods is one of the major focuses in current antiferromagnetic spintronics. In this work, we investigated the ferroelectric control of magnetism in AFM L10-MnPt/BaTiO3 bilayers structures by using first-principles calculation. We studied the effect of ferroelectric polarization reversal on magnetic crystalline anisotropy (MCA) of L10-MnPt films with different interface structures. Our results predict a large perpendicular MCA in L10-MnPt films with Pt-O interface, while an in-plane MCA with Mn-O interface when they are interfaced with ferroelectric BaTiO3. In addition, the magnitude of MCA for both interfaces can be modulated efficiently by the polarization reversal of BaTiO3. The ferroelectric control of MCA has been analyzed based on second order perturbation theory, and it can be mainly attributed to the ferroelectric polarization driven redistribution of Pt-5d orbital occupation around Fermi energy. Especially, for Mn-O interface, the N\'eel vector can be switched between in-plane [100] and [110] directions, or even from in-plane to out-of-plane at certain film thickness by reversing ferroelectric polarization. Our results may provide a non-volatile concept for ferroelectric control of N\'eel vector in L10-antiferromagnets, which could stimulate experimental investigations on magnetoelectric effect of antiferromagnets and promote its applications in low-power consumption spintronic memory devices.

Study the effect of symmetrical voltage of electrodeposition and annealing ‎temperature on magnetic properties of Fe-Sn alloy nanowires

In this research, the Fe-Sn alloy nanowires were made by AC electrodeposition method in anodic ‎aluminum oxide (AAO). The effect of different symmetrical voltages of electrodeposition (17.5-32.5 V) ‎and annealing temperature on magnetic and structural properties of Fe-Sn nanowires were investigated. ‎The magnetic properties, morphology, element composition of materials and crystal structure of the ‎nanowires were studied by AGFM, SEM, EDX and XRD, respectively. The results showed that, coercivity ‎field (Hc) and square ratio (Sq) increases by increasing deposition voltage and also, crystallinity of the ‎nanowires and resulting their crystalline magnetic anisotropy increased, but deposition percentage of Sn ‎to Fe reduced. The Hc and Sq of prepared nanowires were increased by annealing due to increases in their ‎crystalline structure and crystalline magnetic anisotropy. The most variation in Hc and Sq were achieved ‎for prepared nanowires at 30 V.‎

Robust perpendicular magnetic anisotropy of Co3Sn2S2 phase in sulfur deficient sputtered thin films

Perpendicular magnetic anisotropy (PMA) in magnetic thin films is a fundamental key feature in the design of spintronic devices. As one of magnetic Weyl semimetals, ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ has been studied for its large anomalous Hall effect (AHE), uniaxial crystalline magnetic anisotropy, and half metallicity. In this study, we investigated the effect of off-stoichiometric composition on the PMA and AHE of ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{x}$ thin films fabricated by the sputtering technique. The prepared thin films have off-stoichiometric S compositions $x$ of 1.54 (S poor) and 3.27 (S rich) as well as the nearly stoichiometric one of 2.02. In addition to the ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ phase, the segregated Co metal is found to contribute to the measured magnetization in the S-poor and S-rich films. The coercive field of perpendicular magnetization in all the films is much larger than that in the ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ bulk crystals despite the fact that effective perpendicular magnetic anisotropy constants (${K}_{\mathrm{u}}^{\mathrm{eff}}$) between the prepared films are significantly different. In addition, the ${K}_{\mathrm{u}}^{\mathrm{eff}}$ values of two samples with $x=2.02$ and 2.22 are comparable to those of the bulk crystals. In contrast to the isotropic magnetization behavior in the S-rich film, the S-poor film holds the PMA feature. This result means that the PMA is more robust in the S-poor film than in the S-rich film. For the electrical transport properties, a large tangent of Hall angle of about 0.2 is observed for both the nearly stoichiometric and the S-poor films. This large tangent of Hall angle demonstrates that the Weyl feature of ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ phase is well maintained even in the S-poor thin films as well as the nearly stoichiometric films although the amount of Co segregation in both S-poor and S-rich films is similar. Our findings on the influence of off-stoichiometry on the PMA and AHE are beneficial to design magnetic devices incorporated with the Weyl features of ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$.

Tuning the crystalline electric field and magnetic anisotropy along the CeCuBi2−xSbx series

We have performed X-ray powder diffraction, magnetization, electrical resistivity, heat capacity and inelastic neutron scattering (INS) to investigate the physical properties of the intermetallic series of compounds CeCuBi$_{2-x}$Sb$_{x}$. These compounds crystallize in a tetragonal structure with space group $P4/nmm$ and present antiferromagnetic transition temperatures ranging from 3.6 K to 16 K. Remarkably, the magnetization easy axis changes along the series, which is closely related to the variations of the tetragonal crystalline electric field (CEF) parameters. This evolution was analyzed using a mean field model, which included anisotropic nearest-neighbor interactions and the tetragonal CEF Hamiltonian. The CEF parameters were obtained by fitting the magnetic susceptibility data with the constraints given by the INS measurements. Finally, we discuss how this CEF evolution can affect the Kondo physics and the search for a superconducting state in this family.

Tuning the crystalline electric field and magnetic anisotropy along the series.

We have performed X-ray powder diffraction, magnetization, electrical resistivity, heat capacity and inelastic neutron scattering (INS) to investigate the physical properties of the intermetallic series of compounds . These compounds crystallize in a tetragonal structure with space group and present antiferromagnetic transition temperatures ranging from 3.6 K to 16 K. Remarkably, the magnetization easy axis changed along the series, which is closely related to the variations of the tetragonal crystalline electric field (CEF) parameters. This evolution was analyzed using a mean field model, which included an anisotropic nearest-neighbor interactions and the tetragonal CEF Hamiltonian. We obtained the CEF parameters by fitting the magnetic susceptibility data with the constraints given by the INS measurements. More broadly, we discuss how this CEF evolution can affect the Kondo physics and the search for a superconducting state in this family.

Estimation of Magnetic Anisotropy of Individual Magnetite Nanoparticles for Magnetic Hyperthermia.

Ideal interaction-free magnetite nanoparticles were prepared, and their magnetic properties were measured to clarify the true nature of magnetic anisotropy of individual magnetite nanoparticles at the nanoscale and to analyze the shape, surface, and crystalline anisotropy contributions. Spherical (17.7 nm), cubic (10.6 nm), and octahedral-shaped magnetite nanoparticles with average sizes ranging from 7.6 to 23.4 nm were synthesized using solution techniques. Then, these nanoparticles were coated with silica at appropriate shell thicknesses to prepare magnetic interaction-free samples, and their noninteractive nature was confirmed through first-order reversal curve diagrams. For these well-isolated nanoparticles, remanent magnetizations of the hysteresis loops are just equal to a half of the saturation magnetization. This result clearly indicates that uniaxial magnetic anisotropy is predominant in each nanoparticle. In order to clarify the details of the uniaxial magnetic anisotropy, the analysis of blocking temperature-switching field distribution diagrams is constructed based on thermal decay curves of isothermal remanent magnetization at various applied fields. The obtained effective magnetic anisotropy constant Keff is distributed around 10-20 kJ/m3 and has insignificant size dependence. This result seems inconsistent with the inverse proportion relation of Keff with size predicted for surface magnetic anisotropy. The theoretical calculation suggested that the crystalline magnetic anisotropy plays a major role in magnetic properties of the magnetite nanoparticles at lower temperatures. However, it should be noted that Keff seems slightly different for the different shapes. The above study indicates that control size, shape, and interparticle interactions is required to strictly discuss such delicate differences of magnetic anisotropy of individual magnetite nanoparticles for the design of thermal seeds for magnetic hyperthermia.

Systematic exploration of magnetic mechanism of La3Co29Si4B10 by first principles calculation

Rare earth transition metal compounds with intrinsic and high-performance magnetic behaviors have been attractively research topic as a promising permanent magnets material. In particularly, La3Co29Si4B10 is one of typically rare earth ferromagnetism materials with large magnetic moment and high transition temperature. In order to investigate the magnetic origin of sublattice and guide the design of permanent magnet materials with high magnetic moment and high magnetic crystalline anisotropy, we adopt first principles calculations method to investigate the magnetic mechanism of La3Co29Si4B10 combine local coordination environment with density of states. The results show that the magnetic moment mainly comes from the Co atom. According to the different local symmetry and atom hybridization, the Co atoms at different crystal positions can be divided into high spin state with maximum local magnetic moment at 2c position, low spin state with minimum magnetic moment at 8i1 position and medium spin state corresponding moderate magnetic moment size at other positions. Furthermore, the strain-stress of La3Co29Si4B10 will increase the total magnetic moment. Spin orbital coupling calculation indicate that the easy magnetization direction of La3Co29Si4B10 is along in plane with magnetic crystalline anisotropy energy of 0.68 meV/unit cell, which agreement with experimental. Our calculations lay a theoretical foundation for further experimental design of high-performance permanent magnet materials.

Lattice strain caused magnetism and magnetocrystalline anisotropy in Zn modified barium hexaferrite

The Rietveld refinement of XRD patterns reveals the crystallization of all the materials (BaFe12-xZnxO19 for x = 0.0, 0.2, 0.4, and 0.6) to hexagonal symmetry with space group P63/mmc. The lattice strain created in the crystal due to the ionic size mismatch of Zn and Fe. The Law of Approach (LA) to saturation method is employed to obtain the saturation magnetization (Ms) and magnetocrystalline anisotropy constant (K1) from M−H hysteresis loop. The maximum saturation Magnetization (Ms) and minimum coercivity are found to be for BaFe11·8Zn0·2O19 (i.e., x = 0.2). The magnetocrystalline anisotropy constant (K1) reduces with the increase in temperature. The magnetic properties and magnetic crystalline anisotropy in Zn modified barium hexaferrite have been explained by considering the strain in the lattice site and superexchange interaction.

Design and Optimization of Skyrmion-Based Racetrack Memory by Overcoming Clogging and Annihilation of Skyrmion Signals

Magnetic skyrmions are promising building blocks for next generation data storage due to their stability, small size and extremely low currents to drive them. Skyrmion-based metallic racetrack memory has potential to replace traditional domain walls to store information as data bits, in which, however, skyrmions can drift from the direction of electron flow due to the Magnus force. In addition, skyrmion-edge effect at the end of the racetrack can cause the clogging of the skyrmions at the end of the racetrack. Here, we show that the clogging of skyrmion signals can be avoided by adding various kinds of notch at the end of the racetracks. On the other hand, by adding high-[Formula: see text] materials (materials with high magnetic crystalline anisotropy) at the edges, the skyrmions can be confined in the center region of the metallic racetrack successfully. This design can overcome the problems of both clogging and annihilation according to our micromagnetic simulation. As a result, skyrmions can pass the right end of the racetrack efficiently at a very high speed (100–300[Formula: see text]m/s), whereas the driving current is much smaller in comparison with other racetrack design. Besides, we study the influence of the uneven part at the joint of the high-[Formula: see text] material and the CoPt racetrack on the skyrmionic motion. It is found that at the joint between the high-[Formula: see text] material and the CoPt racetrack, the concave part basically does not affect the passage of skyrmion, but the convex part does when the length and width of the convex part reach a certain value. The results show that the design has high feasibility.