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Fe-based amorphous and nanocrystalline alloys, such as FINEMET and its improved variants, are highly valued as green energy-saving materials due to their unique magnetic properties, including high permeability, low coercivity, and near-zero saturation magnetostriction. These characteristics have enabled their extensive use in power electronics and information technology. However, the full potential of these alloys remains unfulfilled due to insufficient understanding of their stress sensitivity. This study focuses on the development history, heat treatment, annealing processes, chemical composition, and underlying mechanisms of Fe-based amorphous and nanocrystalline alloys, aiming to provide insights into stress-induced magnetic anisotropy and guide the development of greener and more efficient soft magnetic materials.

The field dependences of the differential magnetic susceptibility of structural alloy steel 38KhS (an analogue of EN 1.7220 steel) are measured after quenching followed by tempering at temperatures ranging from 500 to 750°C and cold plastic deformation by tension. It is found that in highly tempered samples (above 600°C), at relative elongations exceeding 2%, features such as kinks and additional maxima appeared on the curves. The critical fields of irreversible displacement of the 90° domain walls and the fields of induced magnetic anisotropy have been calculated. Their values allow an estimation of the residual stress levels in the studied samples.

This report is on the nature of strain in thin films of yttrium iron garnet (YIG) on yttrium aluminum garnet (YAG) substrates due to film-substrate lattice mismatch and the resulting induced magnetic anisotropy. Films with thickness 55 nm to 380 nm were deposited on (100), (110), and (111) YAG substrates using pulsed laser deposition (PLD) techniques and characterized by structural and magnetic characterization techniques. The in-plane strain determined to be compressive using X-ray diffraction (XRD). It varied from −0.12% to −0.98% and increased in magnitude with increasing film thickness and was relatively large in films on (100) YAG. The out-of-plane strain was tensile and also increased with increasing film thickness. The estimated strain-induced magnetic anisotropy field, found from XRD data, was out of plane; its value increased with film thickness and ranged from 0.47 kOe to 3.96 kOe. Ferromagnetic resonance (FMR) measurements at 5 to 21 GHz also revealed the presence of a perpendicular magnetic anisotropy that decreased with increasing film thickness and its values were smaller than values obtained from XRD data. The PLD YIG films on YAG substrates exhibiting a perpendicular anisotropy field have the potential for use in self-biased sensors and high-frequency devices.

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. To use skyrmions to store information, an effective method for writing and deleting them is required. Here, Chen et al demonstrate the writing and deleting of skyrmions at room temperature by using hydrogen adsorption to change the magnetic anisotropy of the metallic multilayer hosting the skyrmions.

Magnetic microwires can present excellent soft magnetic properties and a giant magnetoimpedance effect. In this paper, we present our last results on the effect of postprocessing allowing optimization of the magnetoimpedance effect in Co-rich microwires suitable for magnetic microsensor applications. Giant magnetoimpedance effect improvement was achieved either by annealing or stress-annealing. Annealed Co-rich presents rectangular hysteresis loops. However, an improvement in magnetoimpedance ratio is observed at fairly high annealing temperatures over a wide frequency range. Application of stress during annealing at moderate values of annealing temperatures and stress allows for a remarkable decrease in coercivity and increase in squareness ratio and further giant magnetoimpedance effect improvement. Stress-annealing, carried out at sufficiently high temperatures and/or stress allowed induction of transverse magnetic anisotropy, as well as magnetoimpedance effect improvement. Enhanced magnetoimpedance ratio values for annealed and stress-annealed samples and frequency dependence of the magnetoimpedance are discussed in terms of the radial distribution of the magnetic anisotropy. Accordingly, we demonstrated that the giant magnetoimpedance effect of Co-rich microwires can be tailored by controlling the magnetic anisotropy of Co-rich microwires, using appropriate thermal treatment.

Voltage control of magnetic anisotropy in nanoscale heterostructures plays a pivotal role in the design and realization of magnetic random-access memories. To achieve low-voltage operation with high reversibility, we introduce an ion-conducting TiO2 layer capable of storing lithium ions atop a Ta/Pt/CoNi heterostructure. During the discharging process, lithium ions migrate into the TiO2 layer. The resulting interfacial electric field between TiO2 and CoNi induces a reversible evolution of magnetic anisotropy from the out-of-plane direction toward the in-plane direction. Within a voltage window of 1.5 V (from 3.0 V to 1.5 V), both remanent magnetization and coercivity are suppressed to zero. Furthermore, consecutive charge–discharge cycles indicate the reversibility in the modulation of remanent magnetization and coercivity. These findings highlight that ion migration at the magnetic interface enables efficient and reversible control of magnetic anisotropy, opening new opportunities for the development of low-power spintronic devices.

In the field of spintronics, researchers have manipulated magnetization using spin-polarized currents 1 , 2 , 3 . Another option is to use a voltage-induced symmetry change in a ferromagnetic material to cause changes in magnetization or in magnetic anisotropy 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 . However, a significant improvement in efficiency is needed before this approach can be used in memory devices with ultralow power consumption. Here, we show that a relatively small electric field (less than 100 mV nm −1 ) can cause a large change (∼40%) in the magnetic anisotropy of a bcc Fe(001)/MgO(001) junction. The effect is tentatively attributed to the change in the relative occupation of 3 d orbitals of Fe atoms adjacent to the MgO barrier. Simulations confirm that voltage-controlled magnetization switching in magnetic tunnel junctions is possible using the anisotropy change demonstrated here, which could be of use in the development of low-power logic devices and non-volatile memory cells. A voltage-induced symmetry change in a ferromagnetic material can change its magnetization or magnetic anisotropy, but these effects are too weak to be used in memory devices. Researchers have now shown that a relatively small electric field can cause a large change in the magnetic anisotropy of a few atomic layers of iron. The results could lead to low-power logic devices and non-volatile memory cells.

The influence of magnetic anisotropy, post-processing conditions, and defects on the domain wall (DW) dynamics of amorphous and nanocrystalline Fe-, Ni-, and Co-rich microwires with spontaneous and annealing-induced magnetic bistability has been thoroughly analyzed, with an emphasis placed on the influence of magnetoelastic, induced and magnetocrystalline anisotropies. Minimizing magnetoelastic anisotropy, either by the selection of a chemical composition with a low magnetostriction coefficient or by heat treatment, is an appropriate route for DW dynamics optimization in magnetic microwires. Stress-annealing allows further improvement of DW velocity and hence is a promising method for optimization of DW dynamics in magnetic microwires. The origin of current-driven DW propagation in annealing-induced magnetic bistability is attributed to magnetostatic interaction of outer domain shell with transverse magnetization orientation and inner axially magnetized core. The beneficial influence of the stress-annealing on DW dynamics has been explained considering that it allows increasing of the volume of outer domain shell with transverse magnetization orientation at the expense of decreasing the radius of inner axially magnetized core. Such transverse magnetic anisotropy can similarly affect the DW dynamics as the applied transverse magnetic field and hence is beneficial for DW dynamics optimization. Stress-annealing allows designing the magnetic anisotropy distribution more favorable for the DW dynamics improvement. Results on DW dynamics in various families of nanocrystalline microwires are provided. The role of saturation magnetization on DW mobility improvement is discussed. The DW shape, its correlation with the magnetic anisotropy constant and the microwire diameter, as well as manipulation of the DW shape by induced magnetic anisotropy are discussed. The engineering of DW propagation through local stress-annealing and DW collision is demonstrated.

Molecular beam epitaxy (MBE) is a powerful tool in modern technologies, including electronic, optoelectronic, spintronic, and sensoric applications. The primary factor determining epitaxial heterostructure properties is the growth mode and the resulting atomic structure and microstructure. In this paper, we present a novel method for growing epitaxial layers and nanostructures with specific and optimized structural and magnetic properties by assisting the MBE process using electromagnetic and mechanical external stimuli: an electric field (EF), a magnetic field (MF), and a strain field (SF). The transmission of the external fields to the sample is realized using a system of specialized sample holders, advanced transfers, and dedicated manipulators. Examples of applications include the influence of MFs on the growth and anisotropy of epitaxial magnetite and iron films, the use of EFs for in situ resistivity measurements, the realization of in situ magneto-optic measurements, and the application of SFs to the structural modification of metal films on mica.

Thin-film solenoid-type inductors, owning low flux leakage and low parasitic capacitance, is required with high stability and tunability for flexible electronics. The existing solutions for flexible and tunable thin-film solenoid-type inductors is limited with the operations ease, device size and compatibility in flexible electronics. This work demonstrates a general approach to realize thin-film solenoid-type inductors on flexible substrate via stencil lithography. Ultrathin solenoid-type inductors were achieved with the total thickness less than 1 μm, and this ultrathin construction benefited the pliability and deformation uniformity during deformation regulation. The magnetic anisotropy and the permeability of permalloy magnetic core were directly impacted by bending the substrate through the magnetoelastic coupling. Based on this, the applied tensile/compressive strains gave rise to the multi-directional tunability of the thin-film inductors, showing the maximum enhancement over 140% of the inductance value at 800 MHz by bending. With the highly stability over 1,000 bending cycle tests, this method for thin-film solenoid-type inductors with easy-access turnability is expected for the future applications of flexible electronics in RF circuit and wireless communication.