UCLA

Multiferroic materials facilitate the novel development of magnetic devices. Extensive effort has been devoted to the multiferroic field to overcome the scaling limitations in past decades. Likewise, this work focused on increasing energy efficiency and density through the applications, development, and fundamental studies of multiferroics. Application such as cell sorting was proposed to resolve the cell aggregation problem of the conventional method through the permanent magnet. Co/Ni multilayers exhibiting perpendicular magnetic anisotropy (PMA) were designed, fabricated, and tested for the cell sorting application. The cell capture method demonstrates a way towards compact lab-on-a-chip devices for more precise cell sorting control. In this study, we observed an inhomogeneous response across these Co/Ni microdevices. This drove us to investigate the roughness and magnetoelectric effects on the magnetic behavior across the microdevices. The homogenous response is critical to reliable strain-mediated multiferroic devices. We fabricated Co/Ni microdisks on the [Pb(Mg1/3Nb2/3)O3]0.7–[PbTiO3]0.3 (PMN-30PT) substrate, and characterized them using magneto-optic Kerr effect (MOKE) method to obtain the coercivity of each individual microdisks. The results were used to study the dependence on roughness and electric field-induced strain in the substrate. This study aimed to assist the reliable design of strain-mediated PMA based devices. Lastly, an atomic model was developed to understand static and dynamic magnetic behaviors using a multiscale modeling approach. Two Co adatoms on a Cu(100) substrate were modeled by incorporating the atomic displacement effects. The parameters used in the model were extracted from the density functional theory (DFT) calculation. Ferromagnetic to antiferromagnetic transition, and in-plane to out-of-plane switching were observed with changes made to the atomic displacement and applied external field. Additionally, the tunability of the resonance frequency of the two-adatom system was demonstrated with the magneto-displacement effect. The outcome shows that the atomic level devices are promising for the potential application of quantum computing and storage devices. When viewed together, the studies provide the foundational tools to develop next-generation multiferroic devices.