We report giant reversible and permanent magnetic anisotropy reorientation in a magnetoelectric polycrystalline Ni thin film and (011)-oriented ${\left[\text{Pb}\left({\text{Mg}}_{1/3}{\text{Nb}}_{2/3}\right){\text{O}}_3\right]}_{\left(1-\text{x}\right)}–{\left[{\text{PbTiO}}_3\right]}_{\text{x}}$ heterostructure. The electric-field-induced magnetic anisotropy exhibits a 300 Oe anisotropy field and a 50% change in magnetic remanence. The important feature is that these changes in magnetization states are stable without the application of an electric field and can be reversibly switched by an electric field near a critical value $\left(\pm {\mathit{E}}_{\text{cr}}\right)$ . This giant reversible and permanent magnetization change is due to remanent strain originating from a non-180° ferroelectric polarization reorientation when operating the ferroelectric substrate in a specific non-linear regime below the electric coercive field.

We demonstrate in situ 90° electric field-induced uniform magnetization rotation in single domain submicron ferromagnetic islands grown on a ferroelectric single crystal using x-ray photoemission electron microscopy. The experimental findings are well correlated with micromagnetic simulations, showing that the reorientation occurs by the strain-induced magnetoelectric interaction between the ferromagnetic nanostructures and the ferroelectric crystal. Specifically, the ferroelectric domain structure plays a key role in determining the response of the structure to the applied electric field, resulting in three strain-induced regimes of magnetization behavior for the single domain islands.

Stable and efficient guided waves are essential for information transmission and processing. Recently, topological valley-contrasting materials in condensed matter systems have been revealed as promising infrastructures for guiding classical waves, for they can provide broadband, non-dispersive and reflection-free electromagnetic/mechanical wave transport with a high degree of freedom. In this work, by designing and manufacturing miniaturized phononic crystals on a semi-infinite substrate, we experimentally realized a valley-locked edge transport for surface acoustic waves (SAWs). Critically, original one-dimensional edge transports could be extended to quasi-two-dimensional ones by doping SAW Dirac “semimetal” layers at the boundaries. We demonstrate that SAWs in the extended topological valley-locked edges are robust against bending and wavelength-scaled defects. Also, this mechanism is configurable and robust depending on the doping, offering various on-chip acoustic manipulation, e.g., SAW routing, focusing, splitting, and converging, all flexible and high-flow. This work may promote future hybrid phononic circuits for acoustic information processing, sensing, and manipulation.

In this work, we report on the demonstration of voltage-driven spin wave excitation, where spin waves are generated by multiferroic magnetoelectric (ME) cell transducers driven by an alternating voltage, rather than an electric current. A multiferroic element consisting of a magnetostrictive Ni film and a piezoelectric [Pb(Mg_1/3Nb_2/3)O₃]_(1−x)–[PbTiO₃]_x substrate was used for this purpose. By applying an AC voltage to the piezoelectric, an oscillating electric field is created within the piezoelectric material, which results in an alternating strain-induced magnetic anisotropy in the magnetostrictive Ni layer. The resulting anisotropy-driven magnetization oscillations propagate in the form of spin waves along a 5 μm wide Ni/NiFe waveguide. Control experiments confirm the strain-mediated origin of the spin wave excitation. The voltage-driven spin wave excitation, demonstrated in this work, can potentially be used for low-dissipation spin wave-based logic and memory elements.

The ferroelectric properties of (011) [Pb(Mg_1/3Nb_2/3)O₃]_(1−x)-[PbTiO₃]_x (PMN-PT, x≈0.32) single crystals with focus on piezoelectric strain response were reported. Two giant reversible and stable remanent strain states and tunable remanent strain properties are achieved by properly reversing the electric field from the depolarized direction. The unique piezoelectric strain response, especially along the [100] direction, mainly stems from the non-180° ferroelectric polarization reorientation in the rhombohedral phase crystal structure. Such giant strain hysteresis with tunable remanent strain properties may be useful for magnetoelectric based memory devices as well as a potential candidate for other applications.

We report giant reversible and permanent magnetic anisotropy reorientation between two perpendicular easy axes in a magnetoelectric polycrystalline Ni thin film and (011) oriented [Pb(Mg_1/3Nb_2/3)O₃]_(1−x)-[PbTiO₃]_x (PMN-PT) heterostructure. The PMN-PT is partially poled prior to Ni film deposition to provide a remanent strain bias. Following Ni deposition and full poling of the sample, two giant remanent strains of equal and opposite values are used to reversibly and permanently reorient the magnetization state of the Ni film. These experimental results are integrated into micromagnetic simulation to demonstrate the usefulness of this approach for magnetoelectric based magnetic random access memory.