Showing papers on "Magnetic anisotropy published in 2022"
TL;DR: In this article, the physical properties of iron oxide-based magnetic nanoparticles such as Fe3-xO4 and CoxFe3-XO4 are reviewed because of their interest in health, environmental applications, and ultra-high density magnetic recording.
35 citations
TL;DR: In this article , the physical properties of iron oxide-based magnetic nanoparticles such as Fe3-xO4 and CoxFe3-XO4 are reviewed because of their interest in health, environmental applications, and ultra-high density magnetic recording.
30 citations
TL;DR: In this paper , the magnetic anisotropic properties associated with a pentagonal bipyramidal coordination sphere for transition metal and lanthanide ions are examined on the basis of experimental and theoretical investigations.
Abstract: The magnetic anisotropy associated with a pentagonal bipyramidal (PBP) coordination sphere is examined on the basis of experimental and theoretical investigations. The origin and the characteristics of this anisotropy are discussed in relation to the electronic configuration of the metal ions. The effects of crystal field, structural distortion, and a second-coordination sphere on the observed anisotropies for transition meal and lanthanide ions are outlined. For the Ln derivatives, we focus on compounds showing SMM-like behavior (i.e. slow relaxation of their magnetization) in order to highlight the essential chemical and structural parameters for achieving strong axial anisotropy. The use of PBP complexes to impart controlled magnetic anisotropy in polynuclear species such as SMMs or SCMs is also addressed. This review of the magnetic anisotropies associated with a pentagonal bipyramidal coordination sphere for transition metal and lanthanide ions is intended to highlight some general trends that can guide chemists towards designing a compound with specific properties.
26 citations
TL;DR: In this paper , the authors theoretically report an instability toward a skyrmion crystal in centrosymmetric magnets under hexagonal and trigonal single-ion anisotropy.
25 citations
TL;DR: In this article , the authors demonstrate the reversible field-free writing/deleting of skyrmions at room temperature, via hydrogen chemisorption/desorption on the surface of Ni and Co films.
Abstract: Magnetic skyrmions are topologically nontrivial spin textures with envisioned applications in energy-efficient magnetic information storage. Toggling the presence of magnetic skyrmions via writing/deleting processes is essential for spintronics applications, which usually require the application of a magnetic field, a gate voltage or an electric current. Here we demonstrate the reversible field-free writing/deleting of skyrmions at room temperature, via hydrogen chemisorption/desorption on the surface of Ni and Co films. Supported by Monte-Carlo simulations, the skyrmion creation/annihilation is attributed to the hydrogen-induced magnetic anisotropy change on ferromagnetic surfaces. We also demonstrate the role of hydrogen and oxygen on magnetic anisotropy and skyrmion deletion on other magnetic surfaces. Our results open up new possibilities for designing skyrmionic and magneto-ionic devices.
20 citations
TL;DR: In this article , a unique hydrogen-bonded organic-inorganic framework (HOIF) constructed from a mononuclear cobalt(II) complex, [Co(MCA)2·(H2O)2] (HMCA = 4-imidazolecarboxylic acid), via multiple hydrogen bonding interactions was synthesized and structurally characterized.
Abstract: A unique hydrogen-bonded organic-inorganic framework (HOIF) constructed from a mononuclear cobalt(II) complex, [Co(MCA)2·(H2O)2] (HMCA = 4-imidazolecarboxylic acid), via multiple hydrogen-bonding interactions was synthesized and structurally characterized. The Co(II) center in the HOIF features a highly distorted octahedral coordination environment. Remarkably, the CoII HOIF showed permanent porosity with superior stability as established by combined thermogravimetric analysis (TGA), variable-temperature infrared spectra (IR), variable-temperature powder X-ray diffraction data (PXRD), and a CO2 isotherm. Structural studies reveal that short multiple hydrogen bonds should be responsible for the superior thermal and chemical stability of a HIOF. Magnetic investigations reveal the large easy-plane magnetic anisotropy of the Co2+ ions with the fitted D values being 22.1 (magnetic susceptibility and magnetization data) and 29.1 cm-1 (reduced magnetization data). In addition, the HOIF exhibits field-induced slow magnetic relaxation at low temperature with an effective energy barrier of Ueff = 45.2 cm-1, indicative of a hydrogen-bonded framework single-ion magnet of the compound. The origin of the significant magnetic anisotropy of the complex was also understood from computational studies. In addition, BS-DFT calculations indicate that the superexchange interactions between the neighboring CoII ions are non-negligible antiferromagnetism with JCo-Co = -0.5 cm-1. The foregoing results provide not only a carboxylate-imidazole ligand approach toward a stable HOIF but also a promising way to build a robust single-ion magnet via hydrogen-bond interactions.
20 citations
TL;DR: A series of samarium doped cobalt ferrites with the nominal compositions of CoSmxFe2−xO4 was synthesized using sol-gel auto-combustion method as mentioned in this paper.
17 citations
TL;DR: In this paper , the coordination self-assembly of a neutral cobalt(II) magnetic building block and selective pyridine derivatives as organic linkers has led to two distinct cobalt-II coordination polymers, {Co(DClQ)2(bpy)n (1) and {Co2(DCLQ)4(tpb)n(2)
Abstract: Precise modulation of the structure and magnetic properties of coordination compounds is of great importance in the development of framework magnetic materials. Herein, we report that the coordination self-assembly of a neutral cobalt(II) magnetic building block and selective pyridine derivatives as organic linkers has led to two distinct cobalt(II) coordination polymers, {Co(DClQ)2(bpy)}n (1) and {Co2(DClQ)4(tpb)}n (2) (DClQ = (5,7-dichloro-8-hydroxyquinoline; bpy = 4, 4'-dipyridine; tpb = 1,2,4,5-tetra(4-pyridyl)benzene)). Structural analyses revealed that 1 and 2 are one-dimensional (1D) and 2D coordination polymers containing the same neutral magnetic building block [Co(DClQ)2] bridged by bitopic bpy and tetratopic tpb ligands, respectively. Both the complexes have a distorted octahedral CoN4O2 coordination geometry around each cobalt center offered by the bidentate ligand and organic linkers. Magnetic studies reveal large easy-plane and easy-axis magnetic anisotropy for 1 and 2, respectively. However, because of the weak antiferromagnetic coupling between the bpy-bridged CoII centers, no slow relaxation of the magnetization was observed in 1 under both zero or applied dc fields. Interestingly, complex 2 exhibits slow magnetic relaxation under external fields, indicative of a framework single-ion magnet of 2. Theoretical calculations further support the experimental results and unveil that the D values are +65.3 and -91.2 cm-1 for 1 and 2, respectively, while the magnetic exchange interaction was precisely estimated as -0.16 (1) and -0.009 (2) cm-1. The foregoing results show that the structural dimensionality and magnetic properties can be rationally modified via pre-designed magnetic building blocks and a suitable choice of organic bridging ligands.
16 citations
TL;DR: The complexes [Co(L)]X·S (X = CoCl42- , S = CH3CN (1); X = ZnCl 42- ,S = 2CH3OH (2) and X =...
Abstract: The complexes [Co(L)]X·S (X = CoCl42- , S = CH3CN (1); X = ZnCl42- , S = CH3OH (2)), [Co(L)]X2·S (X = ClO4-, S = 2CH3OH (3) and X =...
16 citations
TL;DR: In this article , a new sacrificial material, SrCoO2.5, is presented, which can be coherently grown with wide range epitaxial strains and crystalline orientations and is also soluble in eco-friendly solutions such as acetic acid, vinegar, and even carbonated drinks.
Abstract: Freestanding oxide nanomembranes have promising applications because of their novel electronic states and flexible crystalline structures. Several materials have been developed as sacrificial layers to exfoliate thin films from substrates via wet‐etching. However, these materials face great challenges in terms of either complicated crystalline structures or corrosive solutions. Here, a new sacrificial material, SrCoO2.5, is presented, which can be coherently grown with wide‐range strains and crystalline orientations and is also soluble in eco‐friendly solutions such as acetic acid, vinegar, and even carbonated drinks. With SrCoO2.5 as the sacrificial layer, high‐quality freestanding ferromagnetic SrRuO3 membranes are achieved from wide‐range epitaxial strains and different crystalline orientations. By investigating the evolution of the magnetic properties of these samples, it is discovered that epitaxial strain causes a distinct modification of the magnetic anisotropy of (001)pc‐oriented SrRuO3 samples, while its influence on the (110)pc and (111)pc samples is insignificant. This study not only demonstrates the freestanding SrRuO3 as a promising material for flexible spintronic devices, but also offers a great opportunity to engineer a wide range of strained and oriented complex oxides for novel freestanding electronics using this newly developed sacrificial material.
15 citations
TL;DR: In this paper , a facile method for synthesizing single-crystal freestanding SrRuO3 (SRO) membranes with controlled crystal structure and orientation using water-soluble Ca3-xSrxAl2O6 sacrificial layers is presented.
Abstract: Flexible magnetic materials with robust and controllable perpendicular magnetic anisotropy (PMA) are highly desirable for developing flexible high-performance spintronic devices. However, it is still challenge to fabricate PMA films through current techniques of direct deposition on polymers. Here, we report a facile method for synthesizing single-crystal freestanding SrRuO3 (SRO) membranes with controlled crystal structure and orientation using water-soluble Ca3-xSrxAl2O6 sacrificial layers. Through cooperative effect of crystal structure and orientation engineering, flexible SrRuO3 membranes reveal highly tunable magnetic anisotropy from in-plane to our-of-plane with a remarkable PMA energy of 7.34*106 erg/cm3. Based on the first-principles calculations, it reveals that the underlying mechanism of PMA modulation is intimately correlated with structure-controlled Ru 4d-orbital occupation, as well as the spin-orbital matrix element differences, dependent on the crystal orientation. In addition, there are no obvious changes of the magnetism after 10,000 bending cycles, indicating an excellent magnetism reliability in the prepared films. This work provides a feasible approach to prepare the flexible oxide films with strong and controllable PMA.
TL;DR: In this article , the van der Waals easy-axis antiferromagnet CrSBr was measured and the resonance frequencies were mapped as a function of the magnitude and angle of applied magnetic field.
Abstract: We report measurements of antiferromagnetic resonances in the van der Waals easy-axis antiferromagnet CrSBr. The interlayer exchange field and magnetocrystalline anisotropy fields are comparable to laboratory magnetic fields, allowing a rich variety of gigahertz-frequency dynamical modes to be accessed. By mapping the resonance frequencies as a function of the magnitude and angle of applied magnetic field, we identify the different regimes of antiferromagnetic dynamics. The spectra show good agreement with a Landau-Lifshitz model for two antiferromagnetically coupled sublattices, accounting for interlayer exchange and triaxial magnetic anisotropy. Fits allow us to quantify the parameters governing the magnetic dynamics: At 5 K, the interlayer exchange field is μ0HE = 0.395(2) T, and the hard and intermediate-axis anisotropy parameters are μ0Hc = 1.30(2) T and μ0Ha = 0.383(7) T. The existence of within-plane anisotropy makes it possible to control the degree of hybridization between the antiferromagnetic resonances using an in-plane magnetic field.
TL;DR: In this article , the magnetic shape anisotropy energy (MSA) of the Monolayer Cr2Ge2Te6 (ML-CGT) has been investigated.
Abstract: Monolayer Cr2Ge2Te6 (ML-CGT) has attracted broad interest due to its novel electronic and magnetic properties. However, there are still controversies on the origin of its intrinsic magnetism. Here, by exploring the electronic and magnetic properties of ML-CGT, we find that the magnetic shape anisotropy (MSA) is vital for establishing the long-range ferromagnetism, except for the contribution from magnetocrystalline anisotropy energy (MCA). Electronic band analysis, combined with atomic- and orbital-resolved magnetic anisotropy from a second-order perturbation theory, further reveals that the MCA of ML-CGT is mainly originated from hybridized Te-py and -pz orbitals. The MSA from magnetic Cr atoms in ML-CGT is larger than MCA, resulting in an in-plane magnetic anisotropy. Noticeably, by constructing a heterostructure (HTS) with ferroelectric Sc2CO2, CGT undergoes an in-plane to out-of-plane spin reorientation via ferroelectric polarization switching, accompanied with an electronic property transition from semiconductor to half-metal. The Curie temperature of CGT/Sc2CO2 HTS can be enhanced to 92.4 K under the ferroelectric polarization, which is much higher than that of pristine ML-CGT (34.7 K). These results not only clarify the contradiction of magnetic mechanism of ML-CGT in previous experimental and theoretical works, but also open the door for realizing nonvolatile magnetic memory devices based on a multifunctional ferromagnetic/ferroelectric HTS.
TL;DR: In this paper , a series of linear sandwich single-ion magnets containing [Er(COT)]+ fragment were selected to probe the magneto-structural correlations using ab initio methods.
Abstract: A series of linear sandwich single-ion magnets containing [Er(COT)]+ fragment were selected to probe the magneto-structural correlations using ab initio methods. For prolate shaped ErIII ion, an equatorially coordinating geometry is preferable to achieve high axial anisotropy. Our calculations confirm that the increasing transversal crystal field (CF) induced by equatorial ligands truly enhances the energy barrier. However, if we continue to strengthen the transversal CF in the equatorial plane, the energy barrier inversely decreases. Our further results show that a medium ligand ring of benzene is preferable for prolate shaped ErIII ion, which can induce the modest energy splitting and the small temperature-assisted quantum tunneling of magnetization. Although the obtained energy barrier of 343.1 cm-1 for our created model [(C6H6)Er(COT)]+ is the largest, it is also much smaller than the DyIII-based compounds.
TL;DR: Magnetic ordered materials based on magnetic nanoparticles (MNPs) possessing distinct and tunable morphological characteristics, magnetic property and excellent magnetic anisotropy, have received tremendous attentions, especially in biomedical fields as discussed by the authors.
Abstract: Magnetic ordered materials based on magnetic nanoparticles (MNPs) possessing distinct and tunable morphological characteristics, magnetic property and excellent magnetic anisotropy, have received tremendous attentions, especially in biomedical fields. This review clearly organized the construction routes used to prepare magnetic ordered materials, including magnetic field-induced arrangement and orderly manufacturing-based construction. By focusing on the most relevant and the latest advances related to the biomedical applications in cell fate research, bio-inspired fabrication, magnetic hyperthermia, and magnetic resonance imaging, the unique advantages of magnetic ordered materials are presented and highlighted compared with magnetic unordered assemblies. Although the biosafety of many MNPs has been approved by Food and Drug Administration, future developments of magnetic ordered materials should be still centered on the safety, functional and structural diversity for interdisciplinary research. The review was concluded with a compelling perspective outlook and non-trivial challenges in future investigation of magnetic ordered materials.
TL;DR: In this paper , the magnetic anisotropy control and dramatic modulation of Curie temperature (Tc) up to 400 K are realized in layered Fe5GeTe2 via the high pressure diamond-anvilcell technique.
Abstract: The technological appeal of van der Waals ferromagnetic materials is the ability to control magnetism under external fields with desired thickness toward novel spintronic applications. For practically useful devices, ferromagnetism above room temperature or tunable magnetic anisotropy is highly demanded but remains challenging. To date, only a few layered materials exhibit unambiguous ferromagnetic ordering at room temperature via gating techniques or interface engineering. Here, it is demonstrated that the magnetic anisotropy control and dramatic modulation of Curie temperature (Tc) up to 400 K are realized in layered Fe5GeTe2 via the high‐pressure diamond‐anvil‐cell technique. Magnetic phases manifesting with in‐plane anisotropic, out‐of‐plane anisotropic and nearly isotropic magnetic states can be tuned in a controllable way, depicted by the phase diagram with a maximum Tc up to 360 K. Remarkably, the Tc can be gradually enhanced to above 400 K owing to the Fermi surface evolution during a pressure loading–deloading process. Such an observation sheds light on the understanding and control of emergent magnetic states in practical spintronic applications.
TL;DR: In this article , the anisotropic energy of a 2D antiferromagnet is greatly enhanced via stacking on a magnetic substrate layer, arising from the sublattice-dependent interlayer magnetic interaction.
Abstract: We show that the anisotropic energy of a 2D antiferromagnet is greatly enhanced via stacking on a magnetic substrate layer, arising from the sublattice-dependent interlayer magnetic interaction that defines an effective anisotropic energy. Interestingly, this effective energy couples strongly with the interlayer stacking order and the magnetic order of the substrate layer, providing unique mechanical and magnetic means to control the antiferromagnetic order. These two types of control methods distinctly affect the sublattice magnetization dynamics, with a change in the ratio of sublattice precession amplitudes in the former and its chirality in the latter. In moiré superlattices formed by a relative twist or strain between the layers, the coupling with stacking order introduces a landscape of effective anisotropic energy across the moiré, which can be utilized to create nonuniform antiferromagnetic textures featuring periodically localized low-energy magnons.
TL;DR: In this paper, a cascaded space confined chemical vapor deposition (CS-CVD) technique was used to synthesize 2D FexGeTe2 ferromagnets with OOP magnetic anisotropy.
Abstract: Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D FexGeTe2 ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown FexGeTe2. As a result, high-quality Fe3GeTe2 and Fe5GeTe2 flakes have been grown selectively using the CS-CVD technique. Curie temperature (TC) of the as-grown FexGeTe2 can be up to ∼ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe5GeTe2 reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe5GeTe2 display the highest conductivity among other FexGeTe2 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.
TL;DR: In this paper , a deterministic field-free SOT switching of perpendicular magnetization is achieved in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy axis.
Abstract: Efficient current‐induced switching of perpendicular magnetization is an essential task in spintronics for realizing high‐performance information processing and for storage device application. However, the spin‐orbit torque (SOT) by injection of in‐plane polarized spins cannot deterministically switch the magnetization of ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) without an additionally applied in‐plane external magnetic field to break the symmetry of the PMA. Considering the difficulties of applying the magnetic field to the localized area only within a device structure, it is essential to contrive a facile field‐free SOT switching mechanism. Here, deterministic field‐free SOT switching of perpendicular magnetization is achieved in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy axis. This tilted anisotropy originates from the combined contributions of many internal anisotropies in different orientations from the multilayers and is shown to be controllable. It is expected that the introduction of controlled tilted anisotropy into Gd/Co multilayers over the entire film surface in the present study can be extended to the development of wafer‐scale technologies for the spintronics memory and logic devices.
TL;DR: In this paper , 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm.
Abstract: The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.
TL;DR: In this article, the effect of heat treatment of Co-based amorphous microwires at temperatures near the crystallization onset on micromagnetic structure, magnetostriction, and magnetoimpedance was investigated.
TL;DR: In this article, the authors investigated the crystal structure, microstructure, and magnetic properties of BFCO samples, and the potential application value at millimeter waveband was discussed.
TL;DR: In this article , the authors used magnetometry and ferromagnetic resonance to quantitatively study magnetic anisotropy with an easy axis both in the film plane and perpendicular to it.
Abstract: Magnetometry and ferromagnetic resonance are used to quantitatively study magnetic anisotropy with an easy axis both in the film plane and perpendicular to it. In the study of single-layer and multilayer permalloy films, it is demonstrated that these methods make it possible not only to investigate the average field of perpendicular and in-plane anisotropy, but also to characterize their inhomogeneity. It is shown that the quantitative data from direct integral and local measurements of magnetic anisotropy are consistent with the direct and indirect estimates based on processing of the magnetization curves. The possibility of estimating the perpendicular magnetic anisotropy constant from the width of stripe domains in a film in the transcritical state is demonstrated. The average in-plane magnetic anisotropy field of permalloy films prepared by magnetron sputtering onto a Corning glass is almost unchanged with the thickness of a single-layer film. The inhomogeneity of the perpendicular anisotropy field for a 500 nm film is greater than that for a 100 nm film, and for a multilayer film with a total permalloy thickness of 500 nm, it is greater than that for a homogeneous film of the same thickness.
TL;DR: Control the uniaxial magnetic anisotropy of schreibersite (Fe,Ni)3 P with S4 symmetry by doping and investigate its impact on the stability of antiskyrmions, demonstrating that subtle balance between them is necessary to stabilize the antiskyrsion.
Abstract: Magnetic skyrmions, vortex‐like topological spin textures, have attracted much interest in a wide range of research fields from fundamental physics to spintronics applications. Recently, growing attention is also paid to antiskyrmions emerging with opposite topological charge in non‐centrosymmetric magnets with D2d or S4 symmetry. In these magnets, complex interplay among anisotropic Dzyaloshinskii–Moriya interaction, uniaxial magnetic anisotropy, and magnetic dipolar interactions generates various magnetic textures. However, the precise role of these magnetic interactions in stabilizing antiskyrmions remains to be elucidated. In this work, the uniaxial magnetic anisotropy of schreibersite (Fe,Ni)3P with S4 symmetry is controlled by doping and its impact on the stability of antiskyrmions is investigated. The authors’ magnetometry study, supported by ferromagnetic resonance spectroscopy, shows that the variation of the Ni content and slight doping with 4d transition metals considerably change the magnetic anisotropy. In particular, doping with Pd induces easy‐axis anisotropy, giving rise to formation of antiskyrmions, while a temperature‐induced spin reorientation is observed in an Rh‐doped compound. In combination with Lorentz transmission electron microscopy and micromagnetic simulations, the stability of antiskyrmion as functions of uniaxial anisotropy and demagnetization energy is quantitatively analyzed, and demonstrated that subtle balance between them is necessary to stabilize the antiskyrmions.
TL;DR: In this paper, a mean-field simulation of the magnetocaloric effect of EuGd2O4 and EuDy 2O4 is presented, where the second Dy sublattice is parallel to the crystallographic c-axis.
TL;DR: In this paper , self-intercalated Cr(1+δ)Te2 nanolayers are epitaxially grown on MoS2 (0001), forming prototypical van der Waals heterostructures.
Abstract: Cr(1+δ)Te2 are pseudo-layered compounds consisting of CrTe2 transition metal dichalcogenide (TMD) layers with additional (δ) self-intercalated Cr atoms. The recent search for ferromagnetic 2D materials revived the interest into chromium tellurides. Here, Cr(1+δ)Te2 nanolayers are epitaxially grown on MoS2 (0001), forming prototypical van der Waals heterostructures. Under optimized growth conditions, ultrathin films of only two TMD layers with a single intercalated Cr-layer are achieved, forming a 2D sheet with van der Waals surfaces. Detailed compositional and structural characterization by scanning tunneling microscopy, grazing incidence x-ray diffraction, and high-resolution Rutherford backscattering indicate the layer-by-layer growth and that the δ can be tuned by post-growth annealing in a range between ∼0.5 and 1. X-ray magnetic circular dichroism and magnetometry measurements demonstrate that all self-intercalated Cr(1+δ)Te2 nanolayers exhibit strong ferromagnetism with magnetic moments larger than 3μB per Cr-atom. The magnetic properties are maintained in the ultrathin limit of a material with a single intercalation layer. Interestingly, the magnetic anisotropy can be tuned from close to isotropic (δ = 1) to a desirable perpendicular anisotropy for low δ values. Thus, the bottom-up growth of these 2D Cr(1+δ)Te2 sheets is a promising approach for designing magnetic van der Waals heterostructures.
TL;DR: In this article , the magnetic anisotropy energy (MAE) and magneto-optical (MO) effects of ferromagnetic multilayers [mono-, bi-, tri-, tetra-, and pentalayer] and bulk [
Abstract: The recent discovery of long-range magnetic orders in atomically thin semiconductors ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ and $\mathrm{Cr}{\mathrm{I}}_{3}$ as well as metal ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ has opened up exciting opportunities for fundamental physics of two-dimensional (2D) magnetism and also for technological applications based on 2D magnetic materials. To exploit these 2D metallic magnets, the mechanisms that control their physical properties should be well understood. In this paper, based on systematic first-principles density functional theory calculations, we study the magnetic anisotropy energy (MAE) and magneto-optical (MO) effects of ferromagnetic multilayers [mono-, bi-, tri-, tetra-, and pentalayer] and bulk ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ as well as their connections with the underlying electronic structures of the materials. Firstly, all the considered ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ structures are found to prefer the out-of-plane magnetization and have gigantic MAEs of $\ensuremath{\sim}3.0$ meV/f.u. This gigantic perpendicular anisotropy results from the large magnetocrystalline anisotropy energy (MCE), which is ten times larger than the competing magnetic dipolar anisotropy energy. The giant MCEs are attributed to the large Te ${p}_{x,y}$ orbital density of states near the Fermi level and also to the topological nodal point just below the Fermi level at the K points in the Brillouin zone. Secondly, 2D and bulk ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ also exhibit strong MO effects with their Kerr and Faraday rotation angles being $\ensuremath{\sim}1.{0}^{\ensuremath{\circ}}$ and $\ensuremath{\sim}100 \mathrm{deg}/\ensuremath{\mu}\mathrm{m}$ in the visible-light frequency region, respectively. The strong MO Kerr and Faraday effects are found to result from the large MO conductivity (or strong magnetic circular dichroism) in these ferromagnetic materials. In particular, the calculated MO conductivity spectra are one order of magnitude larger than that of ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. The calculated MO conductivity spectra are analysed in terms of the dipole-allowed optical transitions at high symmetry $\mathrm{\ensuremath{\Gamma}}$, K, and ${\mathrm{K}}^{\ensuremath{'}}$ points, which further indicate that atomically thin ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ films with odd layer-number might exhibit anomalous ferrovalley Hall effect. All these interesting findings thus suggest that 2D and bulk ferromagnetic ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ are promising materials for high-density MO and spintronic nanodevices.
TL;DR: In this paper , the magnetic anisotropy in patterned SrRuO3 (SRO) nanodots as small as 30 nm are studied. And the authors demonstrate a new avenue toward tuning magnetic properties of correlated perovskite oxides and imply that patterned nano-drone could be a promising playground for engineering emergent functional behaviors.
Abstract: Artificial perovskite oxide nanostructures possess intriguing magnetic properties due to their tailorable electron–electron interactions, which are extremely sensitive to the oxygen coordination environment. To date, perovskite oxide nanodots with sizes below 50 nm have rarely been reported. Furthermore, the oxygen octahedral distortion and its relation to magnetic properties in perovskite oxide nanodots remain unexplored thus far. Here, the magnetic anisotropy in patterned SrRuO3 (SRO) nanodots as small as 30 nm are studied. The constituent elements, in particular oxygen ions, are directly visualized via performing atomic resolution electron microscopy and spectroscopy. It is observed that the magnetic anisotropy and RuO6 octahedra distortion in SRO nanodots are both nanodot size‐dependent but remain unchanged in the first 3‐unit‐cell interfacial SRO monolayers regardless of the dots’ size. Combined with first principle calculations, a unique structural mechanism behind the nanodots’ size‐dependent magnetic anisotropy in SRO nanodots is unraveled, suggesting that the competition between lattice anisotropy and oxygen octahedral rotation mediates anisotropic exchange interactions in SRO nanodots. These findings demonstrate a new avenue toward tuning magnetic properties of correlated perovskite oxides and imply that patterned nanodots could be a promising playground for engineering emergent functional behaviors.
TL;DR: Wang et al. as mentioned in this paper proposed a new strategy to control grain growth and magnetic anisotropy, by introducing isotropic compressive stress field in the annealing process to optimize the magnetic properties.
TL;DR: In this paper, the magnetization correlations in amorphous alloy ribbons Fe-Cu-Nb-Si-B were studied by analysis of approach to magnetic saturation within the random magnetic anisotropy model.