Combinatorial Investigation of Rare-Earth Free Permanent Magnets and Local Control of Magnetic Anisotropy through Strain-Based Heterostructures

Sean Wu Fackler (University of Maryland, College Park)

The speaker will present recently published work on multiferroic heterostructures for efficient memory devices and unpublished work on a combinatorial thin film search for rare-earth-free permanent magnets. In their multiferroic heterostructure they investigated the local coupling between dense magnetic stripe domains in transcritical permalloy thin films and ferroelectric domains of BaTiO3. After cooling the heterostructure through BaTiO3's Curie temperature, two distinct changes in the stripe domains are observed using magnetic force microscopy. Inverse magnetostriction is shown to account for the changes in magnetic stripe domain direction and changes in magnetic stripe domain width using micromagnetic simulations. In the second topic they fabricated thin film libraries each spanning large composition regions of different Fe-Co-X systems, where X is a transition metal element such as W, Mo, V, and Ta. In the presented work the high-throughput screening method was applied to the Fe-Co-V system, where composition regions near 10 at% V contain the well-known vicalloys. Large magnetization (1000 emu/cm3) and enhanced perpendicular coercive fields (2.6 kOe) are observed at vicalloy compositions. He will compare our thin films to the known bulk vicalloys and discuss their similarities and discrepancies.

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