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One-dimensional nanoribbons usually exhibit considerably different properties compared to their monolayer counterparts due to the formation of edge states and limited width. In this study, we systematically investigate the stability, electronic structures and magnetic properties of CrSiTe 3 single-layer nanoribbons with different edge configurations and ribbon widths using first-principles calculations. The results show that the edge energies (less than 0.4 eV/Å) for all studied CrSiTe 3 nanoribbons are much lower than that of graphene and many transition-metal dichalcogenide nanoribbons, indicating their stability and easy formation. Compared to the CrSiTe 3 monolayer with ferromagnetic semiconductor characteristics, some of CrSiTe 3 nanoribbons (N -SiCr-ZNRs, N -Te-ZNRs, N -TeCr-ANRs and N -Te-ANRs) become half-metal due to the hybridization between the d orbitals of edge Cr atoms and the p orbitals of edge Te atoms. While N -SiTe-ANRs are bipolar magnetic semiconductors, in which the states near Fermi level are localized around the nanoribbons edge. Our results show that CrSiTe 3 single-layer nanoribbons are promising candidates suitable for applications in spintronic devices. • CrSiTe 3 monolayer nanoribbons are studied by first-principles calculation. • CrSiTe 3 monolayer nanoribbons exhibit interesting width- and edge-dependent electronic structures and magnetic properties. • Very low edge energies (less than 0.4 eV/Å) for all studied CrSiTe 3 nanoribbons indicate their stability and easy formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Prediction of antiferromagnetic metal-rich chalcogenide monolayers M 2 X by first-principles calculation. • Néel temperature of M 2 X can reach or even exceed the room temperature. • The monolayers have large perpendicular magnetic anisotropic energy and can be up to 2000 μeV/cell for Hf 2 X. We predict by first-principles calculations a new kind of binary metal-rich chalcogenide monolayers M 2 X (M = Ti, Zr, Hf and X = S, Se, Te), anti-structure of transition metal dichalcogenides, and study their stability, electronic structures and magnetic properties. This system is an intrinsic two-dimensional antiferromagnetic semiconductor. The magnetic ground state can be expressed as ferromagnetic ordering in a M atomic layer with antiferromagnetic coupling between two M atomic layers. The intralayer ferromagnetic ordering originates from the intralayer ferromagnetic d - p x / p y - d super-exchange interaction and the interlayer antiferromagnetism comes from the interlayer d - p z - d antiferromagnetic coupling through chalcogenide elements. The monolayers have large perpendicular magnetic anisotropic energy and can be up to 2000 μeV/cell for Hf 2 X. The anisotropy energy decreases by one order of magnitude when the metal atom M changes from Hf to Ti. In addition, the calculated Néel temperature can reach or even exceed the room temperature. Our findings suggest that the M 2 X may have potential application in the fields of spintronics, and will promote further theoretical and experimental study of the compounds with the anti-structure of transition metal dichalcogenides. [ABSTRACT FROM AUTHOR]

Ferromagnetic/ferroelectric heterostructures provide an effective avenue for designing new functional materials with novel properties by combining the advantages of different materials. In this context, we investigate systematically the structure, electronic properties, and ferromagnetism of CrTeI/In 2 Se 3 heterostructures using the first-principles calculations. Through the incorporation of the ferroelectric In 2 Se 3 , we modulate the magnetocrystalline anisotropy, exchange interactions, Dzyaloshinskii-Moriya interaction, and other key magnetic parameters of the ferromagnetic CrTeI. Consequently, the easy magnetization direction can be reorientated from in-plane to out-of-plane by switching the electric polarization direction. The enhancement of ferromagnetic coupling and the weakening of antiferromagnetic coupling raise the Curie temperature significantly. Simultaneously, the modulation of the magnetic parameters refines the conditions for forming skyrmions in the heterostructures. The findings in this work hold reference value for understanding the ferroelectric control of ferromagnetism and benefit the applications of two dimensional magnetic materials in spintronics. • Magnetic properties and ferroelectric control of bilayer CrTeI/In 2 Se 3 heterostructures. • Spin reorientation is achieved by switching the electric polarization direction. • Curie temperature is increased and the conditions for forming skyrmions is refined in the heterostructures. [ABSTRACT FROM AUTHOR]

We investigate the electronic structure and magnetic properties of layered compounds SrBO 2 (B = Co, Ni, Mn) based on first principles calculations in the framework of density functional theory with GGA+ U method. We compute the phonon dispersion of these compounds to probe the dynamical stability and find that all the compounds are dynamically stable. SrCoO 2 and SrNiO 2 are G-type antiferromagnetic insulators, and SrMnO 2 is an A-type antiferromagnetic conductor. The electronic configurations of 3d orbitals are (d xz ) 2 (d z 2 ) 2 ( d yz ) 1 (d xy ) 1 (d x 2 - y 2 ) 1 and (d xz ) 2 (dy z ) 2 (d z 2 ) 2 (d xy ) 1 (d x 2 - y 2 ) 1 in SrCoO 2 and SrNiO 2 , respectively. SrCoO 2 shows a Jahn-Teller distortion ( a > b ) because the down-spin Co 3d electron occupies the degenerate (d xz , d yz ) levels. Using Monte Carlo simulations based on the Heisenberg model with exchange parameters obtained from first principles calculations, we obtain the Néel temperatures ( T N ) of SrCoO 2 and SrNiO 2 , which are 249 K and 85 K, respectively. [ABSTRACT FROM AUTHOR]

Spin-wave propagation in periodic magnetization-modulated cylindrical nanowires is studied by micromagnetic simulation. Spin wave scattering at the interface of two magnetization segments causes a spin-wave band structure, which can be effectively tuned by changing either the magnetization modulation level or the period of the cylindrical nanowire magnonic crystal. The bandgap width is oscillating with either the period or magnetization modulation due to the oscillating variation of the spin wave transmission coefficient through the interface of the two magnetization segments. Analytical calculation based on band theory is used to account for the micromagnetic simulation results. [ABSTRACT FROM AUTHOR]

We systematically study the strain-tuning effect on the electronic and magnetic properties of single-layer MnTe 2 using first-principles calculations. The calculations show that the unstrained single-layer MnTe 2 is an intrinsic ferromagnetic metal with a perpendicular magnetocrystalline anisotropy. The in-plane biaxial tensile strain greatly enhances the perpendicular magnetocrystalline anisotropy. The orbital-projected spin-orbit coupling energy indicates that the magnetocrystalline anisotropy energy mainly comes from the contribution of the Te atom although its magnetic moment is small. The ferromagnetic interaction between the nearest two Mn atoms is also strengthened significantly by the tensile strain. The Curie temperature increases from 88 K without strain to 440 K at 10% strain. Moreover, the single-layer MnTe 2 becomes a half metal when the tensile strain is larger than 6%. If compressive strain is applied, the single-layer MnTe 2 undergoes a spin reorientation transition from out-of-plane to in-plane magnetization. The compressive strain also induces the transition of the Mn–Mn exchange coupling from ferromagnetic to antiferromagnetic. The intrinsic ferromagnetic properties and the strong strain-tuning effect make the single-layer MnTe 2 a promising candidate for spintronics applications. • Strain effect on ferromagnetism of MnTe 2 monolayers are studied by first-principles calculation. • Curie temperature increases from 88 to 440 K by the tensile strain. • Magnetocrystalline anisotropy energy can be manipulated effectively by the strain. • Spin reorientation transition from out-of-plane to in-plane magnetization occurs under compressive strain. [ABSTRACT FROM AUTHOR]

• Ni 80 Fe 20 /Pt bilayer nanostrips are fabricated via electron beam lithography and ion beam etch method. • DW depinning under the combined action of magnetic field and electrical current are studied experimentally. • The relationship between the DW depinning and the polarity of transverse DW or chirality of vortex DW is revealed. • Micromagnetic simulations are used to illustrate the DW depinning mechanism. We study the domain wall depinning from a triangle-shaped notch in Ni 80 Fe 20 /Pt bilayer nanostrips using electrical detection technique. It is found that for the 630 nm wide strip, the depinning fields are distributed in a narrow range. While for the 300 nm wide strip, the depinning fields are distributed in two distinctly separated ranges. Micromagnetic simulations show that for the 630 nm wide strip, the depinning corresponds to vortex domain wall, while for 300 nm wide strip, the depinnings of both the vortex wall and the transverse wall are observed. The chirality of vortex wall and the polarity of transverse wall have strong influence on the depinning field. Electrical current has a clear impact on the depinning, but its influence is different for different wall configuration. It can decrease or slightly increase the depinning field of the vortex domain wall depending on the wall chirality and the current direction. The depinning field of the transverse domain wall exhibits an oscillation variation with the current density. Compared to the depinning process of the domain wall in a control sample Ni 80 Fe 20 /Au, it can be inferred the current influence on the domain wall depinning is caused mainly by the current-induced spin-orbit torque. [ABSTRACT FROM AUTHOR]

The Black Phosphorus (BP) nanosheets were prepared by liquid ultrasonic exfoliating the grinded layered BP bulk in organic solutions under protecting atmosphere. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as selective electron diffraction (SED). The possible magnetic (Fe, Co, Ni) impurities in the BP material were analyzed by an inductively coupled plasma-atomic emission spectrometry (ICP-AES). Magnetization measurements were performed using a vibrating sample magnetometer (VSM, Quantum Design PPMS-9T). The results indicate that the BP nanosheets sample has a weak ferromagnetic ordering with high magnetization 1.83 emu/g at room temperature. Analysis states the ferromagnetism is intrinsic to the BP samples, ruling out extrinsic ferromagnetism arising from magnetic metal impurities. The combination effects of magnetic moments resulting from defects or vacancies, the formation of edge states and the p orbital spin polarization of the oxygen and phosphorus atoms of the surface P O bonds contribute to the observed ferromagnetism in BP nanosheets sample. The conversion of ferromagnetism of 2D material BP at room temperature will be of great implication for spintronics application in the future. [ABSTRACT FROM AUTHOR]

We study the nonlinear gyrotropic motion of a magnetic skyrmion in a nanodisk by means of micromagnetic simulations. The skyrmion is driven by a linearly polarized harmonic field with the frequency of counterclockwise gyrotropic mode. It is found that the motion of the skyrmion displays different patterns with increasing field amplitude. In the linear regime of weak driving field, the skyrmion performs a single counterclockwise gyrotropic motion. The guiding center of the skyrmion moves along a helical line from the centre of the nanodisk to a stable circular orbit. The stable orbital radius increases linearly with the field amplitude. When the driving field is larger than a critical value, the skyrmion exhibits complex nonlinear motion. With the advance of time, the motion trajectory of the skyrmion goes through a series of evolution process, from a single circular motion to a bird nest-like and a flower-like trajectory and finally, to a gear-like steady-state motion. The frequency spectra show that except the counterclockwise gyrotropic mode, the clockwise gyrotropic mode is also nonlinearly excited and its amplitude increases with time. The complex motion trajectory of the skyrmion is the result of superposition of the two gyrotropic motions with changing amplitude. Both the linear and nonlinear gyrotropic motions of the skyrmion can be well described by a generalized Thiele’s equation of motion. [ABSTRACT FROM AUTHOR]

We study spin wave propagation in a new type of magnonic crystal consisting of a series of periodically distributed magnetic domain walls in a nanostrip by micromagnetic simulation. Spin wave bands and bandgaps are observed in frequency spectra and dispersion curves. Some bandgaps are caused by the Bragg reflection of the spin wave modes at the Brillouin zone boundaries, while others originate from the coupling between different incident and reflected spin wave modes. The control of the spin wave band structure by changing the magnetocrystalline anisotropy or applying an external magnetic field is studied. Increasing the magnetocrystalline anisotropy leads to an increase of the bandgaps. The external field applied perpendicular to the nanostrip gives rise to a doubling of the domain-wall magnonic crystal period. As a result, more bandgaps appear on the frequency spectra of propagating spin waves. The results presented here may find their use in the design of reconfigurable magnonic devices. [ABSTRACT FROM AUTHOR]

We study the dynamic properties of magnetic nanoelements with tapered ends by using micromagnetic simulations. It is found that the spin-wave modes can be effectively manipulated by the element shape. With the increase of the end sharpness (described by tapering parameter h ), the frequency of the spin-wave edge mode increases rapidly and its oscillation areas in the both ends of element gradually increase and move toward to the central area. Finally, the edge mode completely merges into the fundamental mode. During the magnetization reversal processes, the edge mode experiences one or two softening depending on h ≤60 nm or 60 nm< h <100 nm. When h >100 nm, it is the fundamental mode that goes to zero at the switching field. The evolution of the spin-wave modes reflects the change of the micromagnetic structures of the elements during the reversal. It is the softening of the edge mode that triggers the magnetization reversal in elements with h <100 nm. The quasi-uniform reversal in the elements with h >100 nm is induced by the softening of t h e fundamental mode, where the edge mode is completely suppressed. The results presented in this work demonstrate that the dynamic properties and the magnetization reversal can be effectively tuned by changing the shape of the nanoelements and may be useful for designing the nanoscale magnetic devices. [ABSTRACT FROM AUTHOR]