Static and dynamic spin properties in antiferromagnetic thin films and heterostructures

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Non-Technical DescriptionSpintronics is an active field of research which looks at utilizing the spin of electrons for use in information processing and storage technology. Antiferromagnetic materials are important for speeding up development of spintronics because they have unique advantages over ferromagnetic materials due to their much faster spin precession dynamics and absence of spontaneous magnetic moment. However, research on antiferromagnetic thin films has been scarce. In this project, the research team comprising world leading experts elucidates important and challenging fundamental issues in thin film antiferromagnetic materials using high-quality materials synthesis, detection of antiferromagnetic spin currents using terahertz sources, antiferromagnetic domain imaging, and terahertz time-domain spectroscopy. The experimental work is complemented with theory calculations. Graduate and undergraduate students including those from including underrepresented minorities are trained with the knowledge and skills needed for future employment in the information technology industry. Technical DescriptionDue to the orders of magnitude faster spin dynamics and absence of spontaneous magnetic moment, thin film antiferromagnets present tremendous challenges in obtaining basic static and dynamic spin properties such as the antiferromagnetic ordering temperature, magnetic anisotropy, magnon dispersion, and damping parameter. In this research, a number of challenging issues are tackled using a suite of powerful capabilities developed in-house or available through collaborations with the world leading experts. These include epitaxial thin film and heterostructure growth by pulsed laser deposition and molecular beam epitaxy, detection of antiferromagnetic spin currents via spin Seebeck effect and terahertz spin pumping using both solid state terahertz source and free-electron laser, antiferromagnetic domain imaging with scanning diamond Nitrogen Vacancy-center microscope, and terahertz time-domain spectroscopy. The antiferromagnetic material properties are analyzed in conjunction with density functional theory. Specifically, the project follows the following plan: (1) grow high-quality epitaxial antiferromagnetic thin films and heterostructures for accurately determining and efficiently manipulating the antiferromagnetic order parameter; (2) generate, transport, and electrically detect spin currents in antiferromagnetic thin films both thermally and resonantly to obtain anisotropy, exchange strength, and damping parameters; and (3) control antiferromagnetic static and dynamic properties via growth and external stimuli.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.