Electric field driven multi-state magnetization switching in triangular nanomagnets on piezoelectric substrate.

Electric field control of magnetic state switching mediated by magneto-elastic coupling in multiferroic heterostructures consisting of shape anisotropic magnetostrictive nanomagnets elastically coupled with a piezoelectric substrate has a promising potential for next generation magneto-elastic memory and logic devices. In this work, by using micromagnetic simulation, we showed that localized strain-induced magnetic anisotropy caused by the electric field-induced piezostrain combined with strong multifold shape anisotropy effect can be used for achieving a multistate switching of magnetization in a triangular soft magnetic nano-island on a piezoelectric substrate. A piezostrain-induced uniaxial magnetic anisotropy pulse applied in specific directions switches the magnetization within the triangular nanomagnet by an angle of 60° from the initial state. The relation between critical magnitude of the strain pulse for the switching of the magnetization states and geometric parameters (thickness and lateral size) within the triangular nanomagnets has been worked out. Complete cycles of clockwise as well as counter-clockwise switching of the magnetization states of the triangular nanomagnet have been achieved by a series of sequential switching with different directions of applied strain-induced magnetic anisotropy. This local gating scheme-based multistate switching can be used for electric field-induced ultra-fast, deterministic and reversible magnetization switching which are the key challenges in designing of the magnetoelastic and/or magnetoelectric memory and logic devices.