For a giant magnetostrictive rod under the action of multiple physical loads, such as an external magnetic field, temperature and axial pre-stress, this paper proposes a general one-dimensional nonlinear magneto-thermo-mechanical coupled constitutive model. This model is based on the Taylor expansion of the elastic Gibbs free energy of giant magnetostrictive material and thermodynamic relations from the perspective of macro continuum mechanics. Predictions made using this model are in good agreement with experimental data for magnetization and the magnetostrictive strain curve under the collective effect of pre-stress and temperature. Additionally, the model overcomes the drawback of the existing magneto-thermo-mechanical constitutive model that cannot accurately predict the magnetization and magnetostrictive strain curve for different temperatures and pre-stresses. Furthermore, the constitutive model does not contain an implicit function and is compact, and can thus be applied in both situations of tensile and compressive stress and to both positive and negative magnetostrictive materials, and it is thus appropriate for engineering applications. Comprehensive analysis shows that the model fully describes the nonlinear coupling properties of a magnetic field, magnetostrictive strain and elasticity of a magnetostrictive material subjected to stress, a magnetic field and heat.

For magnetostrictive rods under combined axial pre-stress and magnetic field, a general one-dimension nonlinear magneto-elastic coupled constitutive model was built in this paper. First, the elastic Gibbs free energy was expanded into polynomial, and the relationship between stress and strain and the relationship between magnetization and magnetic field with the polynomial form were obtained with the help of thermodynamic relations. Then according to microscopic magneto-elastic coupling mechanism and some physical facts of magnetostrictive materials, a nonlinear magneto-elastic constitutive with concise form was obtained when the relations of nonlinear strain and magnetization in the polynomial constitutive were instead with transcendental functions. The comparisons between the prediction and the experimental data of different magnetostrictive materials, such as Terfenol-D, Metglas and Ni showed that the predicted magnetostrictive strain and magnetization curves were consistent with experimental results under different pre-stresses whether in the region of low and moderate field or high field. Moreover, the model can fully reflect the nonlinear magneto-mechanical coupling characteristics between magnetic, magnetostriction and elasticity, and it can effectively predict the changes of material parameters with pre-stress and bias field, which is useful in practical applications.

The magnetic skyrmion-based spin transfer nano-oscillators have been set as microwave signal emitters and gaining in popularity due to their performance and integrability in the existing CMOS process flow. In this work, we report our investigations on the strain-modulated magnetization precession in the breathing mode skyrmion-based spin transfer nano-oscillator, which strains from the juxtaposed piezoelectric materials. The strain-modulated skyrmion breathing frequency can be strongly controlled by biaxial-isotropy in-plane strain, in which the tunable range varies from $500\hspace{0.17em}\mathrm{MHz}$ to $7\hspace{0.17em}\mathrm{GHz}$ under the fixed current density $-4\hspace{0.17em}\times {10}^{12}\hspace{0.17em}\mathrm{A}/{\mathrm{m}}^2$ and varying strain from $-2000\hspace{0.17em}\mathrm{ppm}$ to $4000\hspace{0.17em}\mathrm{ppm}$ . Such tunability is external magnetic free and even does not reduce the dynamic resistance variation. Through this method, a promising digital binary frequency shift-key and amplitude shift-key modulation technique are presented, in which the magnetization precession frequency and amplitude can be tuned with the co-action of current and strain pulses. These findings are providing an optional route to design future tunable spin transfer nano-oscillators based on skyrmion with better performance in the wireless communication.

A small‐size reconfigurable smartphone antenna using a PIN diode for WWAN/LTE and global navigation satellite system (GNSS) smartphone application is presented. When the diode is in ‘OFF’ state, a T‐shaped feeding strip and an encircled T‐shaped parasitic shorted strip formed a coupled‐fed antenna, which achieves a low‐wideband covering GSM850/900 bands and a high‐wideband covering GSM1800/1900/UMTS2100/LTE2300/2500 bands. When the diode is in ‘ON’ state, a loop antenna working at 1/2 wavelengths is formed to cover the bands of GNSS, which includes four positioning systems (COMPASS, GALILEO, GPS and GLONASS). In addition, the proposed antenna is easily printed on a small ground clearance of 375 mm ² without loading any lumped element. Also, the proposed simple and compact antenna is convenient to be optimised for desired bands. Finally, the good agreement of simulated and experimental results proves that the proposed antenna is suitable for practical mobile terminal equipment.

The magnetic radial vortex is a nanoscale magnetization configuration that is typically stabilized by the interfacial Dzyaloshinskii–Moriya interaction (i-DMI). The existing control methods for the radial vortex core polarity rely on the use of current flow or magnetic fields, which may cause long consumption times or limit device miniaturization. Here, we investigate a repeated reversal of a radial vortex that can be driven by strain from a piezoelectric substrate using micromagnetic simulations. A phase diagram for the representative regions against perpendicular anisotropy, i-DMI, and the applied strain was obtained. The derived phase diagram was used to associate the mechanism of the core reversal with edge magnetization rotation during core magnetization switching, which exhibits a relationship by transforming a quasi-Bloch wall into a Néel wall. The existence of the i-DMI effect causes the core polarity and radial chirality of the radial vortex to be reversed simultaneously without resulting in larger core movements. These results offer an alternative and efficient way to achieve core reversal, which is expected to stimulate the radial vortex application in magnetoresistive memory devices.