Search

We show a topological spin texture called "bimeronium" in magnets with in-plane magnetization. It is a topological counterpart of skyrmionium in perpendicularly magnetized magnets and can be seen as a combination of two bimerons with opposite topological charges. We report the static structure and spin-orbit-torque-induced dynamics of an isolated bimeronium in a magnetic monolayer with frustrated exchange interactions. We study the anisotropy and magnetic field dependences of a static bimeronium. We also explore the bimeronium dynamics driven by the damping-like spin-orbit torque. We find that the bimeronium shows steady rotation when the spin polarization direction is parallel to the easy axis. Moreover, we demonstrate the annihilation of the bimeronium when the spin polarization direction is perpendicular to the easy axis. Our results are useful for understanding the fundamental properties of bimeronium structures and may offer an approach to build bimeronium-based spintronic devices. [ABSTRACT FROM AUTHOR]

Magnetic multiwalled carbon nanotube (MWCNTs) nanocomposites have been created by the assembly of Mg-Ni-Ti substituted barium ferrite nanoparticles onto surface of MWCNTs. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to demonstrate the successful attachment of ferrite nanoparticles to MWCNTs. Vibrating sample magnetometer (VSM) confirms the relatively strong dependence of saturation of magnetization and coercivity with the volume percentage of MWCNTs. Reflection loss evaluations indicated that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers. [ABSTRACT FROM AUTHOR]

Substituted strontium ferrite (\SrFe12-x{(\Cr0.5\Al0.5)}_x\O19) thin films were formed along the surface of multiwalled carbon nanotubes (MWCNTs). Mössbauer spectroscopy indicates that the substituted cations preferentially occupy the 12k sites. X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), and vector network analyzer were used to analyze the structure, static, and high-frequency magnetic properties of the prepared samples. It was found that with an increase in substitution content, the saturation of magnetization decreases while the coercivity increases. The CNTs could enhance the real and imaginary parts of permittivity of ferrites. With an increase in volume percentage of MWCNTs, the reflection loss values were increased. [ABSTRACT FROM AUTHOR]

By introducing artificial pinning sites to locally modify coercivity in perpendicularly magnetized TbFeCo wires, strip domains were constructed without expense of specimen damage. The construction of strip domains with well-defined shape and controllable number enables a determination of magneto-resistance contributing from singe domain wall. Contrast to crystalline materials, a rather high domain wall magneto-resistance ratio near 20% was found at room temperature, indicating the amorphous TbFeCo is a potential candidate for spintronic devices. [ABSTRACT FROM AUTHOR]

The microstructure and magnetic properties of Nd-Fe-B films with thicknesses from 100 nm to 3 nm have been investigated. All the films show excellent perpendicular magnetic anisotropy with a squareness ratio of 1 in the perpendicular direction and almost zero coercivity in the in-plane direction. Of particular interest is that the initial magnetization curves sensitively depended on the film thickness. Films thicker than 15 nm show steep initial magnetization curve. Although the films have coercivities larger than 21 kOe, the films can be fully magnetized from the thermally demagnetized state with a field as small as 5 kOe. With the decrease of film thickness to 5 nm, the initial magnetization curve becomes flat. The evolution of initial magnetization curves with film thickness can be understood by the microstructure of the films. Films with thickness of 15 nm show close-packed grains without any intergranular phases. Such microstructures lead to steep initial magnetization curves. On the other hand, when the film thickness decreased to 3 nm, the film thickness became nonuniform. Such microstructure leads to flat initial magnetization curves. [ABSTRACT FROM AUTHOR]

Zn1 - xCoxFe2O4 (x = 0-1 in a step of 0.2) nanoparticles with different range of particle size including 5-10 nm and 200-250 nm have been prepared by sol-gel process. Mössbauer spectra at room temperature indicated that, with increasing cobalt content, there is a transition from paramagnetic to magnetically ordered-ferrimagnetic state. Magnetic properties were measured at 300 and 10 K using a Quantum Design MPMS-5S SQUID magnetometer. It was found that with an increase in cobalt content the saturation magnetization and coercivity increase. [ABSTRACT FROM AUTHOR]

Energy harvesting is getting significant interest due to the emergence of Internet of Things (IoT). As IoT devices are required to generate power on their own, several researchers are studying ferroelectric materials for voltage generation. However, ferroelectric materials suffer from high resistance at low frequencies, which reduces the output power. Domain wall propagation in ferromagnetic materials, as induced by stress and a pickup voltage using coils, is investigated as an alternate form of energy harvesting. Such studies, which are reported in multiferroic structures, feature a voltage applied to induce the stress, which defeats the purpose of self‐power generation. Here, power generation from mechanical vibrations in purely ferromagnetic structures is shown. These results are achieved by showing that the domain walls can be moved entirely by stress in a trilayer stack of ferromagnetic microwires. The use of flexible substrates with low Young's modulus and a trilayer magnetic stack enables the achievement of significant magnetization rotation or domain wall motion even from ambient vibrations. Here, the rotation of magnetization or domain wall motion is exploited to induce voltages in the pickup coils. The results shown here provide an alternative way to power IoT devices. Energy harvesting is experimentally demonstrated based on domain wall motion in magnetic microwires. FeCo‐based microwires with an anisotropy in the transverse direction change their magnetization to the longitudinal direction with the application of stress. Such a change in magnetization in the presence of a time‐varying stress could be harvested as voltage for pico‐Internet of Things devices. [ABSTRACT FROM AUTHOR]

A magnetic skyrmionium is a skyrmion-like structure, but carries a zero net skyrmion number which can be used as a building block for non-volatile information processing devices. Here, we study the dynamics of a magnetic skyrmionium driven by propagating spin waves. It is found that the skyrmionium can be effectively driven into motion by spin waves showing a tiny skyrmion Hall effect, whose mobility is much better than that of the skyrmion at the same condition. We also show that the skyrmionium mobility depends on the nanotrack width and the damping coefficient and can be controlled by an external out-of-plane magnetic field. In addition, we demonstrate that the skyrmionium motion driven by spin waves is inertial. Our results indicate that the skyrmionium is a promising building block for building spin-wave spintronic devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] Co2+ substituted lithium ferrite. [•] Structure changes from order to disorder. [•] Coercivity increased with Co2+ substitution. [•] Blocking temperature increased whereas Curie temperature decreased with Co2+ substitution. [Copyright &y& Elsevier]