Recent research work
Robust ultra-small high mobility skyrmions in ferrimagnetic multilayers
Skyrmions are excellent candidates for racetrack memory and synaptic devices. However, skyrmion movement in ferromagnets (FM) is hindered by their transverse movement (skyrmions Hall effect, SkHE) and pinning at defects. We propose a robust amorphous-ferrimagnetic system, where SkHE and pinning were both considerably mitigated. We followed a strategy previously used to generate dense, small skyrmions in FM- employing two DMI generating interfaces of Ir/Fe-FiM and Co-FiM/Pt. The DMI at the two interfaces being additive, strengthens the total DMI and provides a robust, tunable FiM system capable of hosting, high density,, ultra-small, high-mobility skyrmions
Topological Spin Textures Stabilized by the Dzyaloshinskii-Moriya Interaction
The three-dimensional structure of nanoscale topological spin textures stabilized by the Dzyaloshinskii-Moriya interaction is governed by the delicate competition between the exchange, demagnetization, and anisotropy energies. The quantification of such spin textures through direct experimental methods is crucial towards understanding the fundamental physics associated with their ordering, as well as their manipulation in spintronic devices. Lorentz transmission electron microscopy technique was used to quantify mixed Bloch-N´eel chiral spin textures stabilized by the Dzyaloshinskii-Moriya interaction in Co/Pd multilayers. This approach provides the necessary framework for the application of quantitative Lorentz phase microscopy to a broad array of topological spin systems.
SOT driven magnetization switching with sputtered TI spin current source
Current induced spin orbit torques (SOTs) offer an efficient pathway to manipulate the magnetization of a ferromagnet for future magnetic memories and logic devices. Among the various non-magnets utilized, the topological insulators, such as Bi2Se3, have proven to be one of most efficient spin current generators for SOTs. So far, the preferred growth technique for such materials is the molecular beam epitaxy technique which is not compatible with the magnetic memory industry. In this study, we utilize a sputter deposited Bi2Se3 to demonstrate highly efficient SOT generation and subsequently magnetization switching.
BPM by phase transformation with low-energy proton irradiation
Nano-patterning on the order of sub-10 nm is integral to achieve high-density nano-scale devices for various data storage and data processing applications. However, the additional requirement of planarization and unwanted side-effects of physical or chemical etching have so far limited the patterning of sub-10nm devices. In this work, we have demonstrated the creation of an array of 10nm ferromagnetic islands through selective phase transformation of paramagnetic multilayers by low-energy proton irradiation. Therefore, phase transformation by low energy proton irradiation can be used for patterning sub-10nm nano-islands, not only for magnetic data storage but also for patterning various opto-electronic and spintronic devices.
Magnetic Properties of the Free Layer in Double-Barrier Magnetic Tunnel Junctions (p-MTJ)
it is important to understand the Co-Fe-B composition dependence of the magnetic properties of Co-Fe-B-MgO systems. This work focuses on the data-storing free layer of double-barrier magnetic tunnel junctions with perpendicular magnetic anisotropy (PMTJs), which include ultrathin films sandwiched between two MgO layers and a W insert layer. Different CoFeB compositions and annealing conditions can produce highest anisotropy energy to ensure high thermal stability, while maintaining the lowest Gilbert damping parameter which is essential to achieve a low critical switching current. This work provides a better understanding of metal-oxide systems with desirable properties for DBL PMTJ applications.