NSF Award
2425567
Nontechnical<br/><br/>The energy consumption associated with computing has increased dramatically in the past decade due to rapid development of new technologies, where a substantial amount of energy is wasted in the standby state of modern transistors. In this project, the team explores a novel class of devices based on a special quantum mechanical property of electrons called spin. Information stored by spins can last even after the power is turned off, enabling development of highly efficient memory or logic devices. This team studies devices where the spins in magnetic materials point in different directions, resulting in a zero net magnetization. In these so-called antiferromagnetic devices, very interesting properties such as large on/off ratio and energy efficient operation have been predicted. This project combines theoretical research to identify the best antiferromagnetic systems and unveil new physical mechanisms with experimental fabrication and characterization of their unique properties and implementation in computer memory systems. This project supports at least six Ph.D. students and offers research experiences to undergraduate students in all three participating universities. The workforce development and outreach plans include development of new degree programs and hosting teachers from Title I high schools.<br/> <br/>Technical<br/><br/>An emerging class of magnetic tunnel junctions (MTJs) based on antiferromagnets (AF-MTJ) is explored in this project. The principal investigators study novel AF-MTJs with a holistic codesign approach, where physics, materials, device and system-level research are synergistically integrated. Complementary metal oxide semiconductor (CMOS) - compatible processes are employed to fabricate AF-MTJs on (earth-abundant) Si wafers, making results of this project ready to be transferred to industry. In addition to the investigation of the new tunneling magnetoresistance (TMR) phenomenon based on momentum-dependent spin polarization, the PIs investigate spin-transfer torques (STT) and voltage controlled magnetic anisotropy (VCMA) effects in AF-MTJs. This project focuses on antiferromagnetic materials with noncollinear spin configurations, where large TMR ratios have already been predicted by the team through first-principles calculations. Combinatorial growth of films and wafer-level structural and magnetic characterization are employed to enable rapid identification of the best materials. In addition, TMR, STT and VCMA effects with direct currents are probed by a unique method based on conducting atomic force microscopy in sub-100nm devices that can be rapidly fabricated, providing very useful insight for the subsequent RF characterization of fully patterned devices in the dynamic region down to 100ps.<br/><br/>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.
