µ-BLS characterization of reconfigurable voltage-controlled magnonics crystal at the sub-micron scale

Magnonics is receiving considerable attention as it promises miniaturized low-power-consuming information technologies thanks to the spin wave precession with only momentum transmission without moving charges and the nanoscale wavelength of spin waves at giga-hertz frequencies. Magnonic crystals provide the ability to engineer magnon band structures with bandgaps and establish magnon channels via the periodic modulation of the internal field, offering more flexibility for miniaturized magnonic devices application. Reconfigurability is key to magnonics devices to achieve multiple functions such as frequency filtering. However, at the sub-micron scale, magnonics crystals are mostly achieved by bottom-up nanofabrication and challenging to reprogram as the patterning is unalterable. Here, we create a reprogrammable magnonics crystal by combining ferromagnets with multiferroics which is capable of implementing voltage-control. The magnonic crystal was constructed in a thin-film multiferroic bismuth ferrite BiFeO3 (BFO)- lanthanum strontium manganite La2/3Sr1/3MnO3 (LSMO) heterostructure by imprinting a periodic remnant electrical polarization in the multiferroic BFO layer which modulates the effective magnetic field seen by the magons in the LSMO layer. We characterize the spin wave propagation spectra in this artificial, voltage-induced magnonic crystal and demonstrate using µ-BLS the occurrence of a robust magnonic bandgap indicating a filtering effect. The imprinted ferroelectric domains can be reconfigured repeatedly and are robust. Our results open a new path for the function of transduction and reconfigurable filtering of spin waves by CMOS compatible voltage control. In general, by bridging between the scientific fields of functional oxides and magnonics, we propose new perspectives for the development of beyond CMOS based technologies.