title: Nanoscale magnetic ratchets based on shape anisotropy.
abstract: Controlling magnetization using piezoelectric strain through the magnetoelectric effect offers several orders of magnitude reduction in energy consumption for spintronic applications. However strain is a uniaxial effect and, unlike directional magnetic field or spin-polarized current, cannot induce a full 180° reorientation of the magnetization vector when acting alone. We have engineered novel 'peanut' and 'cat-eye' shaped nanomagnets on piezoelectric substrates that undergo repeated deterministic 180° magnetization rotations in response to individual electric-field-induced strain pulses by breaking the uniaxial symmetry using shape anisotropy. This behavior can be likened to a magnetic ratchet, advancing magnetization clockwise with each piezostrain trigger. The results were validated using micromagnetics implemented in a multiphysics finite elements code to simulate the engineered spatial and temporal magnetic behavior. The engineering principles start from a target device function and proceed to the identification of shapes that produce the desired function. This approach opens a broad design space for next generation magnetoelectric spintronic devices.
authors.forename: Jizhai
authors.initials: J
authors.lastname: Cui
authors.forename: Scott M
authors.initials: SM
authors.lastname: Keller
authors.forename: Cheng-Yen
authors.initials: CY
authors.lastname: Liang
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Carman
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Lynch