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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2024)

As the demand for high-performance, energy-efficient, and scalable computing solutions continues to rise, understanding the role of magnetism in computing, especially as we scale down, has become increasingly critical. This dissertation investigates the Dzyaloshinskii-Moriya Interaction (DMI), a chiral magnetic interaction crucial for the deterministic control of nanoscale thin film materials with perpendicular magnetization, which is essential for next-generation memory devices. DMI, an antisymmetric exchange interaction, is significant in systems with broken local inversion symmetry and substantial spin-orbit coupling. Through the application of symmetry arguments and finite difference micromagnetic simulations, this study explores a novel form of inter-layer DMI, termed Néel Type II. This form is prevalent in films with broken inversion symmetry and out-of-plane (OOP) magnetization gradients. Incorporating Néel Type II terms reveals critical experimental features, such as the manipulation of effective DMI strength and chirality based on gradient characteristics, asymmetry in switching fields under in-plane bias, and spin-current-induced field-free deterministic switching. The findings indicate that gradient-induced Néel Type II effective fields disrupt perpendicular magnetization symmetry and can be tuned with variations in DMI strength and magnetization gradient magnitude.Following these advancements, this dissertation highlights the integration of Néel Type II terms in the design of deterministic Voltage-Controlled Magnetic Anisotropy (VCMA) devices. This addresses the challenge of precise voltage-pulse timing in these devices. Additionally, the dissertation explores an innovative Ising machine based on the VCMA effect in FeCoB/FeCo/MgO bilayers, incorporating Néel Type DMI. This approach leverages DMI-induced chiral coupling via Néel-type domain walls, optimizing energy minimization processes and paving the way for advanced, energy-efficient non-Boolean computational solutions. Overall, this research provides a comprehensive understanding of DMI and its practical applications, making significant contributions to the development of next-generation computing technologies.

    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2023)
    The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction that stabilizes spin chirality. One scientific and technological challenge is understanding and controlling the interaction between spin chirality and electric field. In this study, we investigate an unconventional electric field effect on interfacial DMI, skyrmion helicity, and skyrmion dynamics in a system with broken inversion symmetry. We design heterostructures with a 3d-5d atomic orbital interface to demonstrate the gate bias control of the DMI energy and thus transform the DMI between opposite chiralities. Furthermore, we use this voltage-controlled DMI (VCDMI) to manipulate the skyrmion spin texture. As a result, a type of intermediate skyrmion with a unique helicity is created, and its motion can be controlled and made to go straight. Our work shows the effective control of spin chirality, skyrmion helicity, and skyrmion dynamics by VCDMI. It promotes the emerging field of voltage-controlled chiral interactions and voltage-controlled skyrmionics.
      Cover page: Electric field manipulation of spin chirality and skyrmion dynamic.
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