CAREER: Thermal stability and scaling of nanoscale spin-electronic devices based on novel inverse-Heusler alloys

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Many high-tech gadgets from smartphones to laptops employ nanoscale electronic switches for their functionality that rely exclusively on the charge property of the electron. The electron also has another intrinsic property, called spin, which is intuitively analogous to a spinning ball of charge. In the area of spin-electronics, or spintronics, the spin property of electron is exploited to make new devices. For example, the read-head sensor in magnetic hard-disk drives is a spintronic device. The next technology step for spintronics is to realize a spin-switch where the added benefit of non-volatility will be novel compared to charge-based technologies. But several performance-related parameters require significant improvement in order to achieve a nanoscale spin-switch with long lifetime and high energy-efficiency. One approach is to modify the material components inside spintronic devices to address the challenges. Such is the objective of the research plan. Several pre-identified novel magnetic materials and their combinations will be implemented in an advanced spintronic device using thin-film growth and nanoscale device fabrication techniques. The nanoscale spin devices will be characterized for their switching, scaling, energy-efficiency, and speed characteristics to test the feasibility of the materials. Successful implementation of the research plan has the potential for a high payoff and lead to energy-efficient spin-devices. A broad-based training and education of several graduate, undergraduate, and high school students will be accomplished in materials, device physics and device design, fabrication and characterization. The program will actively focus on promoting interest in science, technology and engineering disciplines among undergraduates and local high school students through several synergistic outreach efforts within the local southern Illinois area.Spintronics is recognized as a promising technology to address the scaling problems of current semiconductor devices. In emergent Spin-Transfer Torque Random-Access Memory, parameters such as thermal stability and switching current density, in addition to ON/OFF ratio, are important for such technologies to be viable below the 20 nm node. In this proposal, several new material combinations will be investigated in spin device configurations to directly address the challenging issues of spintronics technology. Several inverse-Heuslers magnetic materials that show perpendicular magnetic anisotropy and high spin-polarization will be investigated. Magnetic Tunnel Junction and Spin-transfer Torque devices will be designed, fabricated and tested for their ON/OFF ratio, switching current/efficiency, and thermal stability. In the initial phase, the tunnel magnetoresistance properties will be tested on micron-scale devices to establish the viability of the various materials combinations. In the second phase of the project, devices will be tested down to sub-20 nm level to investigate the scaling behavior of all relevant parameters. Nanoscale manipulation of spins in a device geometry will be conducted using shape anisotropy. Synergistic interface characterization of fundamental magnetic properties will be accomplished using synchrotron radiation at various national lab facilities. Successful implementation of project goals can lead to greater integration of spintronics technologies into current semiconductor devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.