As traditional electric motors scale down, the available power density rapidly decreases. For a motor occupying a volume of 1 micron cubed, the available power density is roughly six orders of magnitude lower than a 1 millimeter cubed motor. Strain-mediated multiferroic heterostructures have recently been proposed to create high power density, micron scale, magnetic motors. These motors leverage magnetoelastic anisotropy to rotate the magnetic moment of a small disk, and use dipolar forces to couple rotors or beads to the stray magnetic field. A key challenge to the creation of these motors is to deterministically control magnetization rotations without the need for complex fabrication or control schemes. This presentation demonstrates how controlling the relative orientation of magnetic exchange bias and magnetoelastic anisotropies can be used to deterministically control motor rotations over a broad frequency range.
A Stoner-Wohlfarth magnetic macrospin model is created that couples a single domain magnetic disc to a  cut PMN-PT substrate. This model accounts for magnetoelastic, shape, and exchange anisotropy energies. The exchange anisotropy is rotated relative to the biaxial strain created by the PMN-PT substrate. Results demonstrate precessional magnetization dynamics deterministically controlled with an oscillating voltage on the PMN-PT substrate. This approach enables 360 degree rotations over a broad frequency range. The frequency response is provided up through ferromagnetic resonance, and power density calculations are made with comparison to existing micromechanical motors.
John P Domann and Greg P Carman, "Strain mediated multiferroic motors (Conference Presentation)," Proc. SPIE 10165, Behavior and Mechanics of Multifunctional Materials and Composites 2017, 1016517 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 28, 2017; Published: 10 May 2017); https://doi.org/10.1117/12.2263403.5427319330001.
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