LDRD Seminar Series: ‘Tickling Nanoscaled Magnets: High-Frequency Response of Magnetic Metamaterials’
Postdoctoral Researcher M. Benjamin Jungfleisch (MSD) will discuss his Laboratory-Directed Research and Development (LDRD) sponsored work at the LDRD Seminar Series presentation Tuesday, April 11, 2017.
“Tickling Nanoscaled Magnets: High-Frequency Response of Magnetic Metamaterials” will begin at 12:30 p.m. in the Bldg. 203 Auditorium. All are welcome to attend.
In recent years, the exploration of magnons, the quanta of spin waves, as carriers of spin-angular momentum has flourished in spintronics. Magnon spintronics aims at developing novel functional devices that combine magnonic and electronic spin transport phenomena.
In particular, magnetic metamaterials such as artificial spin ice and magnonic crystals offer unique possibilities in magnon spintronics since they allow for tailoring the magnonic properties by design. Artificial spin-ice systems are lithographically defined nanomagnets that mimic effects of frustration, which are characterized by competing interactions that cannot all be simultaneously satisfied. This results in multiple minimal-energy states and rich behaviors that cannot be found elsewhere in nature. Although the exploration of spin ice would be a fascinating playground to investigate how specific magnetization states of individual islands or defects would affect the collective spin dynamics, there are only few works reported on dynamics in these kinds of structures in the high-frequency regime. On the other hand, magnonic crystals are magnetic metamaterials, where their magnetic properties are periodically modified. Similar to photonic crystals, it is possible to engineer well-defined magnonic bandgaps, where the spin-wave propagation in those structures is forbidden.
We recently succeeded in measuring the high-frequency response of a metallic artificial square spin-ice lattice made of permalloy (Ni80Fe20). The nano-scaled bar magnets were patterned using electron beam lithography and measured using broadband ferromagnetic resonance spectroscopy. We observe a rich mode spectrum over the full frequency field/range and find an excellent qualitative agreement of the experiment to a semianalytical model. Furthermore, a hysteretic behavior of modes in the low bias magnetic field regime is observed. Micromagnetic simulations reveal that this field-dependent behavior can be correlated with the magnetization states of individual islands. We find indications that it might be possible to determine the spin-ice state by resonance experiments and the results are a first step towards the understanding of artificial geometrically frustrated magnetic systems in the GHz-regime.
However, in order to integrate magnonic and spintronic devices such as artificial spin ices in existing CMOS-based architectures, which rely solely on the electron’s charge, it is of crucial importance to have efficient converters available. This spin-to-charge conversion can be realized by the spin Hall effect. We studied this conversion process in a specific type of a magnonic crystal; a square Ni80Fe20/Pt antidot lattice and find that the dynamics determined by the design of the lattice can also be detected by dc electrical means. Those results have direct implications on the development of future engineered magnonic applications and devices in which an analog signal processing can be realized in the magnetic pathway.
Benjamin Jungfleisch is a postdoctoral appointee in the Magnetic Films Group in the Materials Science Division. His work is in the field of spin dynamics and material properties of magnetic thin films and multilayers. The main focus of his work is on magnon spintronics in nanoscaled devices and structures that use spin currents carried by spin waves. Benjamin received his Ph.D. from the University of Kaiserslautern, Germany. Prior to joining Argonne, Benjamin worked as a visiting researcher at the Universidade Federal de Pernambuco, Brazil and Tohoku University, Japan. In 2016, he was recognized with an honorable mention for the outstanding postdoctoral performance award in the area of basic research.