In-plane Anisotropy Research Articles

Utilizing Diffusion Tensor Imaging to Differentiate High-Grade Gliomas and Solitary Brain Metastases

Abstract Background Brain tumors, encompassing a spectrum of neoplastic disorders, significantly impact patient morbidity and mortality. Distinguishing between high-grade gliomas (HGGs) and solitary brain metastases (SBMs) is crucial for tailored clinical management. Conventional structural magnetic resonance imaging (MRI) faces challenges in this differentiation, leading to the exploration of advanced imaging modalities such as diffusion tensor imaging (DTI). Materials and Methods In this prospective study, 41 patients with solitary enhancing brain lesions underwent total or subtotal resection, confirmed by histopathology. Imaging involved a 3-Tesla MRI scanner, and DTI data were analyzed for metrics including mean diffusivity, fractional anisotropy (FA), axial diffusivity, radial diffusivity, as well as planar, spherical, and linear (CL) anisotropy coefficients. Results Peritumoral FA and CL exhibited significant differences (p = 0.0217 and p = 0.039, respectively) between HGG and SBM. The area under the curve for peritumoral FA and CL in differentiating HGG and SBM were 0.2791 and 0.6984, respectively. No significant differences were observed in the other diffusion metrics. Conclusion This study contributes to understanding DTI-derived metrics for HGG and SBM differentiation. Peritumoral FA and CL show promise as potential discriminators, offering insights for enhanced clinical decision-making and treatment planning in brain tumor patients. Future research with larger cohorts and advanced diffusion imaging techniques could further refine these findings.

In-Plane Anisotropy in van der Waals NiTeSe Ternary Alloy.

The anisotropic properties of materials profoundly influence their electronic, magnetic, optical, and mechanical behaviors and are critical for a wide range of applications. In this study, the anisotropic characteristics of Ni-based van der Waals materials, specifically NiTe2 and its alloy NiTeSe, utilizing a combination of comprehensive scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations, are explored. Unlike 1T-NiTe2, which exhibits trigonal in-plane symmetry, the substitution of Te with Se in NiTe2 (resulting in the NiTeSe alloy) induces a pronounced in-plane anisotropy. This anisotropy is clear in the STM topographs, which reveal a distinct linear order of charge distribution. Corroborating these observations, ARPES measurements and DFT calculations reveal an anisotropic Fermi surface centered at the point, which is notably elongated along the ky direction, leading to directional variations in in-plane carrier velocities. Consequently, the Fermi velocity is highest along the kx direction where the linear charge distribution aligns in real space and is lowest along the ky direction. These findings offer valuable insights into the tunability of anisotropic properties in ternary transition metal dichalcogenide systems, highlighting their potential applications in the development of anisotropic electronic and optoelectronic devices.

A Low-Symmetry Copper Benzenehexathiol Coordination Polymer with In-Plane Electrical Anisotropy.

Electrically conductive coordination polymers (ECCPs), particularly those incorporating benzenehexathiol (BHT) ligands, are emerging as a distinctive class of electronic materials with tunable semiconducting and metallic properties. However, the exploration of novel ECCPs with low-symmetry structures and electrical anisotropy remains under development. Here, we report the on-water surface synthesis of a novel ECCP, namely Cu5BHT, which exhibits a low-symmetry structure and unique in-plane electrical anisotropy that differs from the well-known Cu3BHT phase. Utilizing imaging and diffraction techniques, we elucidate the unit cell and crystal structure of Cu5BHT, revealing an asymmetric arrangement of the kagome resembling lattice connected by two different secondary building units: square planar CuS4 and non-planar Cu2S4. Theoretical studies indicate that Cu5BHT is metallic and exhibits in-plane electrical anisotropy due to the structure arranged in interconnected well-conducting CuS4 chains and less-conducting Cu2S4 slabs oriented along single crystal direction. Single-crystal electrical measurements confirm a metallic character characterized by the increase of conductance upon cooling. Notably, the measured conductance along different crystal directions within the ab plane unambiguously reveals a significant anisotropy, with an anisotropic factor reaching ~8. This work demonstrates a novel low-symmetry ECCP and highlights its potential for achieving in-plane electrical anisotropy.

Tunable in-plane conductance anisotropy in 2D semiconductive AgCrP2S6 by ion-electron co-modulations.

In-plane anisotropic two-dimensional (2D) semiconductors have gained much interest due to their anisotropic properties, which opens avenues in designing functional electronics. Currently reported in-plane anisotropic semiconductors mainly rely on crystal lattice anisotropy. Herein, AgCrP2S6 (ACPS) is introduced as a promising member to the anisotropic 2D semiconductors, in which, both crystal structure and ion-electron co-modulations are used to achieve tunable in-plane conductance anisotropy. Scanning tunneling electron microscopy and polarized Raman spectroscopy show the structural anisotropy of ACPS. Electrical transport measurements show that its tunable in-plane conductance anisotropy is related to the ion-electron co-modulations, where Ag ion migration is anisotropic along a axis and b axis. Electrical transport measurements show the semiconducting properties of ACPS, as also supported by photoluminescence results. Moreover, the transfer curves of ACPS showcase large Vg-related hysteresis, which is directionally controlled by anisotropic Ag ion migration. This work offers a possibility of using anisotropic charge transport in functional electronics by ion-electron co-modulations.

Significant reduction of anisotropy in stress relaxation aging and mechanical properties improvement for 2195 Al-Cu-Li alloy subjected to plastic loading

Although the plastic loading can enhance creep deformation and yield strength, the anisotropic Stress Relaxation Aging (SRA) behavior and mechanism under plastic loading remain unclear, which presents a significant challenge in accurately shaping aluminum alloy panels. In this study, the SRA behavior of 2195-T4 Al-Cu-Li alloys were thoroughly studied under initial loading stresses within the elastic (210/250 MPa) and plastic (380/420 MPa) ranges at 180 ℃ by stress relaxation and tensile tests as well as microstructure characterization. The findings reveal that compared with those under elastic loadings, in-plane anisotropy (IPA) values of the stress relaxation amount, yield strength and fracture elongation under plastic loadings are reduced by 60%-80%, 70%-90% and 72%-89%, respectively. Similarly, IPA values of precipitate size in grains and Precipitation-Free Zones (PFZ) width at grain boundaries under plastic loading decrease by 31.4% and 94.4% respectively. These results indicate plastic loading significantly weakens the anisotropic SRA behavior, owing to numerous uniformly distributed fine T1 phases and small IPA values of both T1 precipitates size and PFZ width in various loading directions. Compared with those of elastic loading-aged alloys, yield strength of plastic loading-aged alloys shows high strength-ductility because of the combined effect of closely dispersed fine T1 precipitates, narrowed PFZ and numerous sheared and rotated T1 phases at different locations during tensile process. The uniformly distributed larger Kernel Average Misorientation (KAM) and Schmidt factor values of the plastic loading-aged alloy, as well as the cross-slip generated, also help to enhance the strength and ductility of the alloy.

Infrequent trigonal crystal system CoNb thin films: investigation of growth behavior, microstructure and magnetic properties

Magnetic films with excellent initial permeability, high resonance frequency, suitable anisotropy fields, and well compatibility are highly desirable for on-chip inductors and transformers. Here, Co90Nb10 thin films with different thicknesses are grown on Si substrates of different orientations using an electron beam evaporation technique. A rare trigonal crystal structure of the CoNb films was observed and was virtually unaffected by substrate orientation. Films grown exhibit thickness-dependent magnetic behavior: coercivity initially decreases and then increases, while the in-plane anisotropy field progressively diminishes. Meanwhile, the initial permeability increases initially before decreasing, and the resonance frequency continuously decreases as the thickness increases. The resultant Co90Nb10/Si (111)-50 nm film displays a high μi of 496 and a great fr of 2.1GHz. The improved magnetic performance originates from the smaller crystallite size, smoother surface roughness, and suitable in-plane anisotropy field. Moreover, the in-plane anisotropy transition to the out-of-plane anisotropy in the Co90Nb10 films whose thickness exceeds 70nm, which is attributed to the growth of the coarse columnar grains once the critical thickness is exceeded. This study demonstrates the correlation between the growth behavior, microstructure, and magnetic properties of CoNb thin films, presenting a new potential for utilizing Co-based thin films in high-frequency applications.

Coexistence of altermagnetism and robust ferroelectricity in a bulk MnO wurtzite structure.

Altermagnetism is a new class of material with zero net magnetization, but having a nonrelativistic spin-split band structure. Here, we investigate the multifunctional properties of the hexagonal wurtzite MnO (w-MnO). w-MnO has a direct band gap of 0.39 eV and the altermagnetic behavior is achieved with a spin splitting of up to 188 meV. The bulk w-MnO has an in-plane magnetic anisotropy energy of -0.17 meV per cell along the [100] direction and temperature-dependent magnetization reveals a Néel temperature of around 180 K. Moreover, a maximum spin Hall conductivity of -285(ℏ/e) S cm-1 is obtained at a chemical potential of -0.24 eV. Along with the altermagnetism, we also find a large out-of-plane spontaneous polarization of 76.25 μC cm-2. w-MnO exhibits a low energy barrier of 0.26 eV per formula unit (f.u.) for polarization switching and this is further decreased to 0.15 eV per f.u. under 5% epitaxial tensile strain. The molecular dynamics simulations suggest that w-MnO retains its ferroelectric order below 2100 K indicating excellent thermal stability. These findings suggest that the hexagonal w-MnO can be a promising candidate for multiferroic applications particularly in spintronic and ferroelectric devices with high thermal stability.

Enhanced, broad and thin low-frequency microwave absorption induced by proper magnetic anisotropy in polyhedral SmFeO3-encapsulated Sm2Fe17 nanoparticles

High permeability accompanied with large magnetic loss is considered as an effective strategy for achieving efficient low-frequency absorption. However, it remains a considerable challenge for synergistically improving the permeability and magnetic loss at low frequency range due to the proper magnetic anisotropy. In this study, arc discharge method is proposed to fabricate polyhedral core-shell structured Sm2Fe17 nanoparticles with averaged size of 160nm, in which SmFeO3 with averaged thickness of ~3.5nm works as dielectric shell. The frequency dependence of electromagnetic parameters of 20wt.% Sm2Fe17@SmFeO3 nanoparticles-paraffin composites have been studied at 2-18GHz. Natural resonance frequency reaches 6.64GHz. The real part and imaginary part of initial permeability is up to 2.42 and 0.76, respectively. The composite delivers the minimal reflection loss of -45.36dB at 3.2GHz with 3.0mm and the optimal effective absorption bandwidth of 2GHz (5.84-7.84GHz) with only matching thickness of 1.5mm. The superior low-frequency absorption performances are ascribed to the planar anisotropy field for providing high permeability and the polyhedral structure for suppressing natural resonance movement to mid-high frequencies. Furthermore, radar cross section simulations verify the great potential for practical applications. This work provides a valuable reference for designing microwave absorbers with merits of strong absorption, wide bandwidth and thin thickness in the low frequency range.

Highly Air-Stable N-Doped Two-Dimensional Violet Phosphorus with Atomically Flat Surfaces.

Few-layer violet phosphorus (VP) shows excellent potential in optoelectronic applications due to its unique in-plane anisotropy and high mobility. However, the poor air stability of VP severely limits its practical applications. This article reports highly air-stable VP obtained by a two-step nitrogen plasma treatment where the nitrogen volume flow rate is controlled to coordinate physical etching and chemical doping. Specially, this plasma process can remove partial oxidations formed on the VP surface with barely etching to the intrinsic VP surface but efficiently incorporates nitrogen into VP, resulting in surface nitrogen-doped VP (N-VP) nanosheets with atomically smooth surfaces that exhibit excellent air stability. Atomic force microscopy images show that the N-VP nanosheet, nearing a monolayer thickness, maintained its surface morphology and flatness unchanged in ambient air for over 60 days. The improved stability of N-VP can be partly due to its atomically smooth surface, which reduces the number of active or oxidation sites. Further elucidation was made by density functional theory calculations, showing that this ultrastability may intrinsically be attributed to repairing P vacancies by N dopants. This research provides a feasible strategy for significantly enhancing the durability of VP.

Intrinsic Localized Excitons in MoSe2/CrSBr Heterostructure.

Despite extensive studies on magnetic proximity effects, the fundamental excitonic properties of the 2D semiconductor-magnet heterostructures remain elusive. Here, the presence of localized excitons in MoSe2/CrSBr heterostructures is unveiled, represented by a new photoluminescence emission feature, X*. Our findings reveal that X* originates from excitons confined by intrinsic defects in the CrSBr layer. Additionally, the degrees of valley polarization of the X* and trion peaks exhibit opposite polarities under a magnetic field and closely correlate with the magnetic order of CrSBr. This is attributed to spin-dependent charge transfer across the heterointerface, supported by density functional theory calculations which reveal a type-II band alignment. Furthermore, the strong in-plane anisotropy of CrSBr induces unique polarization-dependent responses in MoSe2 emissions. This study highlights the crucial role of defects in shaping excitonic properties and offers valuable insights into spectrally resolved proximity effects in semiconductor-magnet van der Waalsheterostructures.

Rare-Earth Iron Garnet Superlattices with Sub-unit Cell Composition Modulation.

Oxide superlattices reveal a rich array of emergent properties derived from the composition modulation and the resulting lattice distortion, charge transfer, and symmetry reduction that occur at the interfaces between the layers. The great majority of studies have focused on perovskite oxide superlattices, revealing, for example, the appearance of an interfacial 2D electron gas, magnetic moment, or improper ferroelectric polarization that is not present in the parent phases. Garnets possess greater structural complexity than perovskites: the cubic garnet unit cell contains 160 atoms with the cations distributed between three different coordination sites, and garnets exhibit a wide range of useful properties, including ferrimagnetism and ion transport. However, there have been few reports of the synthesis or properties of garnet superlattices, with layer thicknesses approaching the unit cell dimension of 1.2 nm. Here, we describe superlattices made from Bi and rare earth (RE = Tm, Tb, Eu, Lu) iron garnets (IGs) grown by pulsed laser deposition. Atom probe tomography and transmission electron microscopy reveal the composition modulation without dislocations and layer thicknesses as low as 0.45 nm, less than half a unit cell. TmIG/TbIG superlattices exhibit perpendicular magnetic anisotropy that is qualitatively different from the in-plane anisotropy of the solid solution, and BiIG/LuIG superlattices exhibit ferromagnetic resonance linewidth characteristics of the end-members rather than the solid solution. Garnet superlattices provide a playground for exploring interface physics within the vast parameter space of cation coordination and substitution.

Orientation Influence on Tensile Strain Hardening in Forged Plates of AA2014 Aluminium Alloy

Strain hardening is an effective strengthening method for alloys that requires plastic deformation of the material during manufacturing. The strength will significantly increase due to the number of dislocations formed during plastic flow of material. This study examines the plastic flow activity of forged plates of an AA2014 aluminium alloy with tensile test conditions. The effects of solution treatment and artificial ageing on strain hardening characteristics and tensile behaviour were investigated using tensile testing and scanning electron microscopy. Hollomon plastic flow relationship was employed for solution treated and age hardening conditions by experimental engineering stress- engineering strain data of the aluminium alloy AA2014. In both solution-treated and age-hardened conditions, the alloy displays three distinct strain hardening rate levels. The highest rate of strain hardening occurs both in solution-treated and age hardening conditions in regions with lower strain. It is also noted that specimens experience higher and lower strain hardening rates in the forging direction (Longitudinal, L) and perpendicular to the forging direction (Transverse, T) respectively in both solution-treated and age hardening conditions. In order to bring out the degree of in-plane anisotropy, test are conducted in L, L+45° (45° to L direction) and T in the plane of forging. Lower and higher magnification SEM images of the alloy under study, clearly exhibited that the ductile dimple fracture associated with a lower shear fracture contributions.

Electronic and optical properties of a Ta2NiSe5 monolayer: A first-principles study

The crystal structure, stability, electronic, and optical properties of the Ta2NiSe5 monolayer have been investigated using first-principles calculations in combination with the Bethe–Salpeter equation. The results show that it is feasible to directly exfoliate a Ta2NiSe5 monolayer from the low-temperature monoclinic phase. The monolayer is stable and behaves as a normal narrow-gap semiconductor with neither spontaneous excitons nor non-trivial topology. Despite the quasi-particle and optical gaps of only 266 and 200 meV, respectively, its optically active exciton has a binding energy up to 66 meV and can exist at room temperature. This makes it valuable for applications in infrared photodetection, especially its inherent in-plane anisotropy adds to its value in polarization sensing. It is also found that the inclusion of spin–orbit coupling is theoretically necessary to properly elucidate the optical and excitonic properties of a monolayer.

Magnetoelectric effects in a heterostructure of magnetostrictive fiber composite and piezopolymer film

Abstract Magnetoelectric (ME) effects in composite heterostructures comprising ferromagnetic (FM) and piezoelectric (PE) layers realize mutual transformation of magnetic and electric fields and form the basis for the development of highly sensitive magnetic field sensors, electrically tuned electronic components, and energy harvesting devices. ME effects result from a combination of magnetostriction of the FM layer and piezoelectricity in the PE layer due to mechanical coupling between the layers. In this work ME effects are studied in a flexible heterostructure containing a magnetostrictive fiber composite (MFC) and a piezopolymer layer. MFC is a set of microwires made of amorphous FeCoSiB alloy with high magnetostriction and arranged in a plane parallel to each other in a polymer matrix. MFC exhibits strong in-plane anisotropy of magnetization and magnetostriction resulting from demagnetization effects in microwires. Anisotropy leads to the dependence of the linear and nonlinear ME effects characteristics on the orientation of dc magnetic field in the plane of the heterostructure. For the fabricated heterostructure at the resonance frequency of bending vibrations, a linear magnetoelectric coefficient of 24 V/(Oe∙cm) was obtained, and the efficiency of nonlinear generation of the second voltage harmonic reached 1.6 V/(Oe2∙cm). ME effects in MFC heterostructures can be used to create magnetic field sensors and electronics devices that are sensitive to the field orientation.electronics devices that are sensitive to the field orientation.

Manipulation of Unconventional Spin Polarization in Non-Collinear Exchange-Spring Magnetic Structures.

Manipulating the polarization of spin current is essential for understanding the mechanism of charge-to-spin conversion and achieving efficient electrically driven magnetization switching. Here, a novel exchange-spring magnetic structure is introduced formed by the coupling of perpendicular magnetic anisotropy (PMA) CoTb and in-plane magnetic anisotropy (IMA) Co films. When a spin current with the polarization along the y-direction flows through this exchange-spring (x-z plane) structure, the interaction between the y-spin and the local exchange field with a non-collinear spatial distribution gives rise to substantial unconventional spin polarizations in the x- and z-directions, enabling field-free spin-orbit torque driven perpendicular magnetization switching at room temperature. More importantly, the polarization directions of this unconventional spin current can be reversed depending on whether the interfacial exchange coupling is ferromagnetic or antiferromagnetic. This work establishes a platform to explore emergent mechanisms for manipulating unconventional spin polarization with rich non-collinear magnetic exchange spin structures.

3D Printing of Continuous Basalt Fiber-Reinforced Composites: Characterization of the In-Plane Mechanical Properties and Anisotropy Evaluation.

Usage of continuous fibers as a reinforcement would definitely increase the mechanical properties of 3D-printed materials. The result is a continuous fiber-reinforced composite obtained by additive manufacturing that is not limited to prototyping or non-structural applications. Among the available continuous reinforcing fibers, basalt has not been extensively studied in 3D printing. This material is attractive due to its natural origin, good mechanical properties, impact strength, and high chemical and thermal resistance. In this work, a continuous basalt fiber co-extruded composite obtained by fused filament fabrication was characterized both thermally and mechanically, concerning the in-plane tensile properties. The degree of anisotropy of the material was also assessed, both qualitatively and quantitatively. The 3D-printed composite showed longitudinal properties, which were 15 times higher than the pure matrix, thus meeting structural requirements. On the other hand, transverse and shear properties were much lower than longitudinal ones, thus leading to a strongly anisotropic material. This was also confirmed by the anisotropy evaluation that was performed numerically and graphically using an innovative approach. This behavior affects the design of 3D-printed parts; thus, an optimized continuous fiber deposition is necessary for structural applications.

Intrinsically anisotropic 1D NbTe4 for self-powered polarization-sensitive photodetection

Polarization-sensitive photodetection enhances scene information capture, crucial for modern optoelectronic devices. One-dimensional (1D) materials with intrinsic anisotropy, capable of directly sensing polarized light, are promising for such photodetectors. NbTe4, a quasi-1D transition metal tetra-chalcogenide, offers significant benefits for polarization-sensitive photodetection due to its structural anisotropy. Nonetheless, to date, the anisotropic properties of 1D NbTe4 have not been reported. Herein, NbTe4 nanobelts were synthesized via mechanical exfoliation from needle-like bulk crystals, and their anisotropic and optoelectronic properties were comprehensively studied. Angle-resolved polarized Raman spectroscopy, in conjunction with azimuth-dependent reflectance difference microscopy, confirmed that 1D NbTe₄ exhibits intrinsic structural and in-plane optical anisotropy. The 1D NbTe4 device demonstrated characteristic anisotropic photodetection behavior, achieving dichroic ratios of 1.16 at 671 nm and 1.25 at 1064 nm. Meanwhile, the device exhibits a pronounced photothermoelectric effect, conferring a broad spectral photoresponse ranging from visible to near-infrared wavelengths (532-1064 nm), with a rapid response time of 158 ms. This study demonstrates that NbTe4 inherently possesses in-plane anisotropy, making it a promising candidate for polarization-sensitive photodetection applications.

Fabrication of Pt-Rich CoPt/Co-Rich CoPt Bilayer Films with Perpendicular Magnetic Anisotropy for Vertical Domain Wall Memory

Vertical domain wall memory (V-DWM) is an advanced racetrack memory, whose recording density reaches more than 10 Tb･cm-2 due to the racetracks installed vertically [1]. Conventionally, horizontal racetrack memories have been fabricated by dry etching [2-5]. However, ferromagnetic materials are difficult to etch into high-aspect-ratio structure vertically. Therefore, electrodeposition in nanoholes is a suitable process to fabricate V-DWM. In addition, V-DWM has multilayer structures in the vertical racetracks, which improves controllability of domain walls and lowers power consumptions [1]. In the multilayers, magnetic layers with perpendicular magnetic anisotropy (PMA) and those with weak anisotropy are stacked. CoPt alloy is a candidate for the material of V-DWM because its magnetic anisotropy can be altered by changing its composition [6]. Until now, though Co/Pt multilayer films have been fabricated by electrodeposition [7, 8], they do not have both PMA and high coercivity enough for storage medium. In this study, to establish the method of stacking CoPt layers which can be applied to V-DWM, the bilayer film where PMA Co-rich CoPt layer and Pt-rich one were stacked was fabricated, and its structures and magnetic properties were characterized. At first, monolayer Co-rich CoPt films with PMA were electrodeposited on Pt substrates potentiostatically. The plating bath consisted of 1 mM CoSO4, 0.1 mM H2PtCl6, and 0.1 M Na2SO4. The counter and reference electrodes were Pt mesh and Ag/AgCl. The deposition potential was set to -650 mV. Deposition time was varied from 100 to 1300 s and suitable time for PMA was found. From the results of vibration sample magnetometer (VSM) measurements, the electrodeposited CoPt films showed PMA when the deposition time was from 500 to 700 s, and their easy axis changed into in-plane direction from 1100 s. The coercivity of PMA sample deposited for 500 s was 1.5 kOe. Cross-sectional transmission electron microscope (TEM) images showed the thickness of the CoPt film with PMA deposited for 500 s was 6 nm while that with in-plane magnetic anisotropy deposited for 1300 s was 10 nm. Energy dispersive X-ray spectroscopy (EDS) results showed the composition of Co in deposited films were 70-90 at%. Considering that crystal magnetic anisotropy keeps PMA even if the thickness of CoPt film with almost the same composition is 20 nm [9], the deposited film could have weak crystal magnetic anisotropy, which suggests that interface magnetic anisotropy between the CoPt layer and Pt substrate is the cause of the PMA. Next, Pt-rich layer was deposited on the PMA CoPt layer by changing deposition potential from -650 mV to -500 mV. The deposition time of the Pt-rich layer was 2000 s to design its thickness to be 10 nm. A bilayer structure was observed in a TEM bright field image and EDS mapping. The average compositions of top and bottom layers were Co42Pt58 and Co72Pt28, respectively. The total thickness of the bilayer was confirmed to be 12 nm. From VSM measurements, fabricated the bilayer film showed PMA and its coercivity was 1 kOe. However, PMA in the bilayer film was smaller than that of the bottom Co-rich layer. The reason why PMA was weakened would be that large total thickness of bilayer weakened interface anisotropy. However, smaller Co composition of the top layer than that of the bottom layer decreases demagnetization in the film, which could prevent the easy axis to become in-plane direction. Thus, Pt-rich CoPt/Co-rich CoPt bilayer film with PMA and the coercivity of 1 kOe can be fabricated. With this stacking method, CoPt multilayered structures which can be applied for V-DWM will be fabricated in the future.Acknowledgements This work was supported in party JST Strategic Basic Research Programs CREST (No. JR-MJCR31C1). Also, part of this work was the results of using a research equipment (G1026) shared in MEXT Project for promoting public utilization of advanced research of advanced research infrastructure (JPMXS0440500024).

Influence of an ultrathin Mn ‘spy layer’ on the static and dynamic magnetic coupling within FePt/NiFe bilayers

Abstract We explore whether insertion of an ultrathin Mn ‘spy layer’ within a magnetic hard/soft bilayer can enable depth-sensitive element-specific measurements of the static and dynamic magnetization, while avoiding significant disruption of the original magnetic state. MgO(110)/FePt(100 Å)/NiFe(200 Å)/Mn(t Mn Å)/NiFe(200 Å) samples with Mn thicknesses of t Mn = 0, 5, and 10 Å were fabricated by magnetron sputtering and studied by element-selective x-ray magnetic circular dichroism (XMCD), vector network analyzer ferromagnetic resonance (VNA-FMR), and x-ray detected ferromagnetic resonance (XFMR). For t Mn = 5 Å, the magnetic reversal properties remain broadly similar to t Mn = 0 Å. For t Mn = 10 Å, the two NiFe layers decouple with XMCD hysteresis loops at the Mn edge showing two switching events that suggest the presence of two distinct Mn-containing regions. While the Mn moments within each region have ferromagnetic order, their relative alignment is antiparallel at high field. Analysis of the magnetic data and additional scanning transmission electron microscopy measurements point to the presence of a Mn layer at the lower NiFe/Mn interface, and the formation of a NiFeMn alloy at the upper Mn/NiFe interface. The Mn moments of the former region lie antiparallel to those of the underlying NiFe layer. The VNA-FMR data suggests that for t Mn = 5 and 10 Å, the interfacial exchange coupling at the FePt/NiFe is suppressed and the in-plane uniaxial magnetic anisotropy of the NiFe is increased, perhaps due to migration of Mn towards the buried interface. The above findings show that Mn is a problematic magnetic spy, and that a Mn thickness of less than 5 Å would be required.

5d transition-metal adsorption tailored valley splitting and magnetic anisotropy of Janus 2H-WSSe monolayer

Valley splitting and magnetic anisotropy of 5d TM (Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg) adsorbed Janus 2H-WSSe monolayers are investigated using first-principles calculations. The results show that 5d TM atoms adsorbed on the W-top site of Janus 2H-WSSe monolayer exhibit the lowest adsorption energy, regardless of the Se or S layer. The electronic states of Hf-SW and Re-SeW adsorbed systems cross the EF and show metallicity, while the other adsorbed systems still exhibit the semiconducting characteristics. According to the k·p model based on the effective Hamiltonian, the Zeeman effect arising from the local magnetic moment of 5d TM atoms lifts tunable valley splitting within 12.7–227 meV owing to different SOC strength. A maximum valley splitting of 227 meV is observed in the W adsorbed system, which is large enough to realize the valley Hall effect. Both perpendicular magnetic anisotropy (PMA) and in-plane magnetic anisotropy (IMA) can be adjusted by adsorbing different 5d TM atoms on the S/Se layer. Remarkably, the matrix elements differences (dx2–y2, dxy) decide the PMA and IMA behaviors, which are due to the competition of different TM-d orbitals based on the second-order perturbation theory. These results suggest that the 5d TM adsorbed Janus 2H-WSSe monolayer can be considered a good candidate for the spintronic and valleytronic devices.