Exchange-Mediated Rotation Coherence in Magnetostrictive / Non-Magnetostrictive Strain-Coupled Multiferroics

Multiferroics are widely pursued, as such materials offer a multitude of exciting new device applications. There is a push to develop artificial composite multiferroics since there are few examples of natural multiferroics with room temperature functionality.[1] For strain-coupled multiferroics, voltage control of ferromagnetism can be achieved by interfacing piezoelectric and magnetostrictive materials. Functionality can be extended by exchange coupling the magnetostrictive material to a non-magnetostrictive magnet. Interfacing magnetostrictive Galfenol (Fe_100-xGa_x; x=15-25) with low loss Permalloy (Ni₈₀Fe₂₀) on a PMN-PT substrate results in a strain-coupled system with the potential for quick-switching for high frequency applications. Polarized neutron reflectometry (PNR) was used to measure the electric field dependencies of the structural and magnetic depth profiles for a series of Ni₈₀Fe₂₀ / Fe_100-xGa_x bilayers, and Fe_100-xGa_x / Ni₈₀Fe₂₀ multilayer, grown on PMN-PT. These results are consistent with micromagnetic simulations which suggest a 5% deviation in rotation angle across the entire Fe_100-xGa_x and Ni₈₀Fe₂₀ stack. Thus, we demonstrate coherent electric field response across tens of nm - an optimal range for device applications.

[1] Appl. Phys. Lett. 110, 242403 (2017)