NSF Award
2328787
Nontechnical Description<br/><br/>Antiferromagnets are a class of materials with microscopic magnetic dipole moments that align in the opposite direction of their neighbors. They possess dynamic modes that emerge from microscopic oscillations at frequencies ranging from billions (GHz) to trillions (THz) of cycles per second. This is important for emerging technologies based on THz devices for communications, computing and sensing. Whereas permanent magnets can be magnetized through a magnetic field, antiferromagnets are highly resistant to external control. This makes it difficult to manipulate their magnetic properties and develop new technologies based on these materials. To advance technologies based on antiferromagnets, the research team will synthesize structures designed to effectively excite and manipulate their dynamic properties. The materials focus will be on antiferromagnetic oxides of iron (Fe2O3), chromium (Cr2O3), and nickel (NiO). The team will engineer interactions between the oscillating modes within thin film structures composed of antiferromagnets and other materials. The PI seeks to broaden participation in STEM by involving female undergraduate and graduate students in the laboratory. The PI will also organize seminars and round table discussions where women speakers from industry, with relevant technical backgrounds, engage with the students in both formal and informal settings. The objective is to develop and support a network that empowers women to achieve their career aspirations and provides a broader perspective on how their technical skills can contribute to the STEM workforce.<br/><br/>Technical Description<br/><br/>Within antiferromagnetic materials and metamaterials, magnons exist across a wide range of frequencies, spanning from tens of GHz to THz. However, practical methods to robustly manipulate and excite the antiferromagnetic magnon spectrum at the sub-THz or THz level have yet to be demonstrated. This is primarily due to the insensitivity of antiferromagnetic order to external fields. The functionalization of these ultrafast magnetic excitations holds significant potential for unlocking next-generation THz electronics and ultrafast magnetic memory technologies that are currently nonexistent. The team's approach to functionalize antiferromagnetic magnons combines motifs from spintronics with emerging concepts in hybrid quantum magnonics. Specifically, magnon-magnon interactions between various acoustic and optical modes are leveraged to exert control over the magnon energy spectrum. In this project, sputter deposition techniques are employed to synthesize heterostructures that either emulate antiferromagnets or incorporate bulk antiferromagnets into the overall structure. The heterostructures resembling antiferromagnets are akin to synthetic antiferromagnets, comprising multiple ferromagnetic films coupled together by a non-magnetic spacer material. The total number of magnetic layers and the choice of spacer layer materials in a given structure are key factors in exciting magnons and generating magnon-magnon interactions. By synthesizing heterostructures based on bulk antiferromagnets, the team relies on interactions between spatially uniform antiferromagnetic magnons and short-wavelength ferromagnetic magnons to control the energy level spectrum in the sub-THz and THz regime. Conventional ferromagnetic resonance spectroscopy, spin-torque ferromagnetic resonance spectroscopy, and frequency-domain THz spectroscopy techniques are employed for the characterization of these samples.<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.
