Electric-Field Control of Propagating Spin Waves by Ferroelectric Domain-Wall Motion in a Multiferroic Heterostructure

Customizing Room-Temperature Perovskite Ferroelectrics toward the Multichannel Domain Manipulation

Manipulating domain structure in ferroelectrics by external stimuli presents a fascinating avenue for new-generation electronic devices. However, multichannel controlling of ferroelectric domains is still a challenge, due to the lack of knowledge on their bistability to diverse physical stimuli. Herein, we have customized a series of perovskite ferroelectrics, (CnH2n+1NH3)2(CH3NH3)2Pb3Br10 (n = 2-7), of which the Curie temperatures are modulated in a wide temperature range (ΔT = 74 K) by tailoring chain length of organic spacers. Strikingly, the n = 7 member is a room-temperature ferroelectric with bistable characteristics, thus endowing the manipulation of domains via four channels (i.e., thermal, stress, light, and electric fields). Such a non-volatile memory behavior of the stress-switching domain is unprecedented in hybrid perovskite ferroelectrics. This manipulation of domains reveals the unique bistability of its ferroelectric orders, which sheds light on the future advance of customizing electric-ordered materials toward smart device applications.

Investigation of Composition-Dependent Phonon Spectra in In-Plane Heterostructured Cu(1-x)In(1+x/3)P2S6 by Brillouin Light Scattering

CuInP2S6 (CIPS) is a two-dimensional van der Waals material that is ferrielectric at room temperature (TC of 315 K). This TC can be raised up to 335 K by synthesizing CIPS with Cu deficiencies (Cu1-xIn1+x/3P2S6, CIPS-IPS), which causes the material to self-segregate into separate CIPS and In4/3P2S6 (IPS) domains. Using Brillouin light scattering microscopy, we examine the phonon spectra of CIPS, IPS, and CIPS-IPS (x = 0.2, 0.3, 0.5, 0.6, 0.8) at room temperature and across TC. We observe unique longitudinal acoustic (LA) phonon signatures for pure CIPS and IPS; however, the CIPS-IPS samples host LA phonons corresponding to both CIPS and IPS, due to the formation of the in-plane heterostructures. These phonons soften in CIPS and CIPS-IPS near their respective values of TC, and there are sharp discontinuities in the phonon frequencies at TC, indicative of the ferrielectric-to-paraelectric phase transition. The temperature and width of this transition is dependent on composition, with pure CIPS showing the sharpest transition at 40.0 °C, while reduction in Cu leads to broadening and an increased TC, caused by the strain exerted on the CIPS domains by the IPS domains. This strain also manifests in IPS domains, as the phonons soften to accommodate the structural change in the CIPS domains.

Excitation of Spin Waves by Oscillatory Voltage-Controlled Dzyaloshinskii-Moriya Interaction in Ferroelectric/Skyrmion Heterostructure

Spin waves exhibit high-speed, low-energy information transmission and encoding capabilities. The core component, the spin wave generator, currently faces challenges of high energy consumption and integration difficulties. This study proposes a spin wave generator based on a ferroelectric/ferromagnetic heterostructure. This generator utilizes an electric field to control the Dzyaloshinskii-Moriya interaction (DMI), regulating the dynamics of magnetic topological states like skyrmions, thereby achieving low-power excitation of spin waves. First, we conducted a theoretical analysis to study the impact of oscillatory voltage-controlled DMI on the dynamic properties of skyrmions, identifying the excitation conditions for both the breathing mode and the spin wave mode. Additionally, we clarified the relationship among spin wave intensity, DMI coefficient, and frequency. Finally, we validated the theoretical predictions of the spin wave excitation in this structure through micromagnetic simulations. This work points the way toward developing ultrahigh frequency, low-power, and highly stable spin wave generators.

Optical control of spin waves in hybrid magnonic-plasmonic structures

Magnonics, which harnesses the unique properties of spin waves, offers promising advancements in data processing due to its broad frequency range, nonlinear dynamics, and scalability for on-chip integration. Effective information encoding in magnonic systems requires precise spatial and temporal control of spin waves. Here, we demonstrate the rapid optical control of spin-wave transport in hybrid magnonic-plasmonic structures. By using thermoplasmonic heating in yttrium iron garnet films integrated with gold nanodisk arrays, we achieve a suppression of spin-wave signals by 20 dB using single laser pulses lasting just a few hundred nanoseconds. Our results reveal a strong correlation between plasmonic light absorption and spin-wave manipulation, as supported by micromagnetic simulations that emphasize the crucial role of magnonic refraction. This study establishes thermoplasmonics as a powerful tool for controlling spin-wave propagation, bridging the fields of magnonics and plasmonics, and paving the way for the development of multifunctional hybrid magnonic devices.

Electric Field Switching of Magnon Spin Current in a Compensated Ferrimagnet

Manipulation of directional magnon propagation, known as magnon spin current, is essential for developing magnonic devices featuring nonvolatile functionalities and ultralow power consumption. Magnon spin current can usually be modulated by magnetic field or current-induced spin torques. However, these approaches may lead to energy dissipation due to Joule heating. Electric-field switching of magnon spin current without charge current is highly preferred but challenging to realize. By integrating magnonic and piezoelectric materials, the manipulation of the magnon spin current generated by the spin Seebeck effect in the ferrimagnetic insulator Gd3Fe5O12 (GdIG) film on a piezoelectric substrate is demonstrated. Reversible electric-field switching of magnon polarization without applied charge current is observed. Through strain-mediated magnetoelectric coupling, the electric field induces the magnetic compensation transition between two magnetic states of the GdIG, resulting in its magnetization reversal and the simultaneous switching of magnon spin current. This work establishes a prototype material platform that paves the way for developing magnon logic devices characterized by all electric field reading and writing and reveals the underlying physics principles of their functions.

Electric and Magnetic Tuning of Gilbert Damping Constant in LSMO/PMN-PT(011) Heterostructure

Electric field control of magnetodynamics in magnetoelectric (ME) heterostructures has
been the subject of recent interest due to its fundamental complexity and promising applications in
room temperature devices. The present work focuses on the tuning of magnetodynamic parameters
of epitaxially grown ferromagnetic (FM) La_0.7Sr_0.3MnO₃(LSMO) on a ferro(piezo)electric (FE)
Pb(Mg_0.33Nb_0.67)O₃-PbTiO₃(PMN-PT) single crystal substrate. The uniaxial magnetic anisotropy
of LSMO on PMN-PT confirms the ME coupling at the FM/FE heterointerface. The magnitude of
the Gilbert damping constant (α) of this uniaxial LSMO film measured along the hard magnetic axis
is significantly small compared to the easy axis. Furthermore, a marked decrease in the α values of
LSMO at positive and negative electrical remanence of PMN-PT is observed, which is interpreted
in the framework of strain induced spin dependent electronic structure. The present results clearly
encourage the prospects of electric field controlled magnetodynamics, thereby realising the room
temperature spin-wave based device applications with ultra-low power consumption.

Strain-Tuned Spin-Wave Interference in Micro- and Nanoscale Magnonic Interferometers

Here, we report on the experimental study of spin-wave propagation and interaction in the double-branched Mach–Zehnder interferometer (MZI) scheme. We show that the use of a piezoelectric plate (PP) with separated electrodes connected to each branch of the MZI leads to the tunable interference of the spin-wave signal at the output section. Using a finite element method, we carry out a physical investigation of the mechanisms of the impact of distributed deformations on the magnetic properties of YIG film. Micromagnetic simulations and finite-element modelling can explain the evolution of spin-wave interference patterns under strain induced via the application of an electric field to PP electrodes. We show how the multimode regime of spin-wave propagation is used in the interferometry scheme and how scaling to the nanometer size represents an important step towards a single-mode regime. Our findings provide a simple solution for the creation of tunable spin-wave interferometers for the magnonic logic paradigm.