We simulated the generation and propagation of spin waves (SWs) using two excitation methods, namely, magnetic field and voltage induced strain. A fully coupled non-linear magnetoelastic model, combining Landau–Lifshitz-Gilbert with elastodynamic equations, is used to study the propagation characteristics of SWs in magnetoelastic materials. Simulation results show that for excitation frequencies above ferromagnetic resonance (FMR), SWs excited by voltage induced strain propagate over longer distances compared to SWs excited by magnetic field. In addition, strain mediated SWs exhibit loss characteristics, which are relatively independent of the magnetic losses (Gilbert damping). Moreover, it is also shown that strain induced SWs can also be excited at frequencies below FMR.

Strain-coupled multiferroic heterostructures provide a path to energy-efficient, voltage-controlled magnetic nanoscale devices, a region where current-based methods of magnetic control suffer from Ohmic dissipation. Growing interest in highly magnetoelastic materials, such as Terfenol-D, prompts a more accurate understanding of their magnetization behavior. To address this need, we simulate the strain-induced magnetization change with two modeling methods: the commonly used unidirectional model and the recently developed bidirectional model. Unidirectional models account for magnetoelastic effects only, while bidirectional models account for both magnetoelastic and magnetostrictive effects. We found unidirectional models are on par with bidirectional models when describing the magnetic behavior in weakly magnetoelastic materials (e.g., Nickel), but the two models deviate when highly magnetoelastic materials (e.g., Terfenol-D) are introduced. These results suggest that magnetostrictive feedback is critical for modeling highly magnetoelastic materials, as opposed to weaker magnetoelastic materials, where we observe only minor differences between the two methods’ outputs. To our best knowledge, this work represents the first comparison of unidirectional and bidirectional modeling in composite multiferroic systems, demonstrating that back-coupling of magnetization to strain can inhibit formation and rotation of magnetic states, highlighting the need to revisit the assumption that unidirectional modeling always captures the necessary physics in strain-mediated multiferroics.

Spin waves are of great interest as an emerging solution for computing beyond the limitations of scaled transistor technology. In such applications, the frequency of the spin waves is important as it affects the overall frequency performance of the resulting devices. In conventional ferromagnetic thin films, the magnetization dynamics in ferromagnetic resonance and spin waves are limited by the saturation magnetization of the ferromagnetic (FM) material and the external bias field. High-frequency applications would require high external magnetic fields which limit the practicality in a realistic device. One solution is to couple microwave excitations to perpendicular standing spin waves (PSSWs) which can enable higher oscillation frequencies. However, efficient coupling to these modes remains a challenge since it requires an excitation that is nonuniform across the FM material thickness and current methods have proven to be inefficient, resulting in weak excitations. Here, we show that by creating periodic undulations in a 100-nm-thick ${\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$ layer, high-frequency PSSWs ($>20\mathrm{GHz}$) can be efficiently excited using micrometer-sized transducers at bias fields below 100 Oe which absorb nearly 10% of the input rf power. Efficient excitation of such spin waves at low fields may enable high-frequency spintronic applications using exchange-dominated magnetic oscillations using very low external magnetic fields and, with design optimizations, can bring about alternative possibilities in the field.

Precise control and manipulation of nano-beads have various applications, e.g. cell sorter, 3D printing and nano-motors. In this paper we present an approach in which we use voltage on a piezolecetric substrate in order to reorient the magnetization of a nano-disk. In turn this magnetization drives the dynamic of the nano-beads. This is an energy efficient method to control the nano-beads motion since only voltage is applied to the substrate. The mechanism consists of a Ni disk and three pairs of surface electrodes placed on a PZT substrate. By controlling the voltage applied on the different pairs of electrodes, the magnetization of the Ni disk will rotate with constant angular velocity. The rotating magnetization will then generate magnetic force on the soft-magnetic nano-beads driving the motion. For the beads, full 3D dynamics consider both translation and rotation and the forces considered are magnetic, drag, friction and adhesion. With this model we are able to have a realistic description for the particle behavior.

Terfenol-D has one of the largest magnetoelastic coefficients at room temperature, making it a good candidate for future magnetoelectric memory devices. However, few studies exist on the spin configuration in nanoscale Terfenol-D single domain structures. There are two exchange stiffness parameters of Terfenoal-D reported in the literature. In this paper, we use micromagnetic simulations to evaluate the influence of these two exchange parameters on the spin states of ellipsoidal shapes. Analytical results indicate that these two parameters produce significantly different spin states. Therefore, experiments to more accurately measure the exchange stiffness constant of Terfenol-D are needed.