CAREER: Next-generation Logic, Memory, and Agile Microwave Devices Enabled by Spin Phenomena in Emergent Quantum Materials

The proposed research will impact society through the innovation to realize new device technologies. A program to train next-generation researchers will be pursued. A multi-year mentoring program, which will provide research experience for undergraduate students in the principal investigator’s lab will be established through this research program.

Outreach programs for the public will be developed and will be targeted towards K-12 students in the southwestern Pennsylvania area. In parallel, a course to teach fundamental concepts of quantum physics through hands-on experiments will be developed. This course will provide education to produce the next-generation quantum workforce for emergent industries in the United States.

Emergent phenomena in novel quantum materials are key to enable transformative devices for computing, data storage, and high-frequency electronics. For magnetic memory devices, the proposed research will enable a much sought after two-terminal spin-orbit torque magnetic memory device for energy efficient and ultra-compact data storage. To build an industry competitive magnetic memory device, a small footprint hardware node is desired to implement a dense network of storage elements.

However, spin-orbit torque driven magnetic memory devices considered so far in the field have three terminals, wherein a magnetic tunnel junction is integrated on top of spin-source material to read the state through tunnel-magnetoresistance effect. The spin-orbit torque driven magnetic memory devices are envisioned to be highly energy-efficient because spin current induced by spin Hall effect phenomena is more efficient at magnetization manipulation than spin-polarized current used in magnetic tunnel junction-based devices.

However, a spin-orbit torque based two-terminal device has been critically missing. This research program will demonstrate a prototype spin-orbit torque based two-terminal device for magnetic memory applications in which the magnetic state is read using a new kind of magnetoresistance owing to out-of-plane spin current in Weyl semimetals. Additionally, the electrical tuning of magnetic interactions in two-dimensional magnets can enable agile microwave devices, such as tunable band-pass filters.

Microwave filters based on spin-wave excitations in magnetic materials have the potential to realize functionalities such as compactness, planar, and frequency-agility. However, achieving an electrical turnability of spin-wave excitations, which decides the pass and rejection frequency of a magnet based band-pass filter, is highly desired for microwave devices but it remains challenging.

This research program will explore and demonstrate gate voltage tuning of magnetic anisotropy in two-dimensional magnets for prototyping electric-field tunable band-pass filter devices.

A research program aimed at experimental demonstration of transformative device functionalities for next-generation memory and high-frequency devices using emergent spin-phenomena in Weyl semimetals and two-dimensional magnets will be pursued. The specific scientific goals of this research program are twofold: (1) A two-terminal spin-orbit torque based magnetic memory unit cell will be demonstrated, wherein the information is stored in the magnetic state of ferromagnet with perpendicular magnetic anisotropy, the magnetic state is written by the spin-orbit torque phenomena, and the state is read through a new type of magnetoresistance owing to tilted spin current in Weyl semimetals; (2) An electric-field tunable band-pass filters based on two-dimensional magnets will be demonstrated.

The electric field tunability of magnetic anisotropy to tune the magnetic resonance of a magnet will be explored, which is the key characteristic of a frequency agile band-pass filter because the application of electrical field will shift the location of resonance frequency to set up the pass and rejection band of the proposed microwave device. For proposed band-pass filters, insertion loss, pass-filter center frequency, operational bandwidth, and other device parameters will be characterized.

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.