Spintronics: Putting a spin on electronics for low-power computing (Repeat)

_{Room #}

_{Topic/ Invited Presenter/Position}

_{Title and Abstract}

_Supervisor

1

_{Spin hall materials/devices and magnonics}

_{Jiahao Han}

_{Graduate Student}

_{Gated nonreciprocal magnon transmission from direction-dependent magnetic damping 
An important application of magnetic materials in information processing and communication is to provide nonreciprocity. Conventional ferromagnet-based microwave circulators and optical isolators suffer from their bulk volume and the difficulty of being integrated into high-density circuits. We show that in an on-chip device with a magnetic gate, tunable nonreciprocal propagation can be realized in spin Hall effect-excited magnons with broadband spectrum. We identify a direction-dependent magnetic damping as the origin of the nonreciprocity. Our findings provide a general mechanism for introducing directional magnon transmission and lead to a design of passively gated magnon transistors for emergent chiral magnonic applications.}

_{Prof. Luqiao Liu}

2

_{Spin hall materials/devices and magnonics}

_{Pengxiang Zhang}

_{Graduate Student}

_{Current-induced Switching of Compensated Ferrimagnets and Antiferromagnets
Magnetic random access memories (MRAMs) using compensated ferrimagnets or antiferromagnets as free layers have great potentials of higher density, speed, and power efficiency. The advantages come from the fully compensated magnetic moments, allowing zero stray field and faster magnetic dynamics. Spin-orbit torque, an efficient way to switch ferromagnetic memory bits, may also switch compensated ferrimagnets and antiferromagnets efficiently. For compensated ferromagnets, we demonstrated the spin-orbit torque switching first in Co1-xTbx alloy, and then in Mn2Ru1−xGa, a Heusler alloy with lower damping and higher spin polarization. Furthermore, we clarified the complicated mechanisms of the current-induced switching in the canted antiferromagnet α-Fe2O3.}

_{Prof. Luqiao Liu}

3

_{Spin currents in insulators}

_{Ethan Rosenberg}

_{Graduate Student}

_{Magnetic and spintronic properties of Y-substituted TmIG thin films
Thulium iron garnet (TmIG) has excited great interest due to record-breaking spin orbit torque-driven domain wall velocities over 2 km/s and the presence of the Dzyaloshinskii-Moriya interaction, which stabilizes chiral Néel domain walls. In this study we describe the static and dynamic magnetic properties of yttrium-substituted TmIG (TmYIG) thin films with a variety of Y:Tm ratios grown by pulsed laser deposition. We find that, by varying the Y:Tm ratio over a range of 0-0.67, we can tune the anisotropy energy of the film over three orders of magnitude and observe a transition from PMA to in-plane anisotropy with little change in room temperature magnetization. We relate the anisotropy to the changes in both magnetostriction and strain state vs. composition.}

_{Prof. Caroline Ross}

4

_{Voltage controlled magnetism}

_{Shuai Ning}

_{Post Doc}

_{Voltage-controlled ON/OFF magnetism above room temperative in SrCo1-xFexO3-δ
Searching for new materials and phenomena to enable voltage control of magnetism and magnetic properties holds compelling interest for the development of low-power nonvolatile memory devices. Here, I will present a voltage control of magnetism in epitaxial SrCo1−xFexO3−δ (SCFO). For the Co/Fe ratio of ∼1:1, a switch between nonmagnetic (OFF) and ferromagnetic (ON) states is accomplished by ionic liquid gating at ambient conditions with voltages as low as ±2 V. Tuning the oxygen stoichiometry enables reversible and continuous control of the magnetization between 0 and 100 emu/cm3 at room temperature.}

_{Prof. Caroline Ross}

5

_{Quantum Materials for Future Spintronics}

_{Hang Chi}

_{Post Doc}

_{Surface/Interface Driven Novel Topological Phenomena
Surfaces/interfaces are pivotal for uncovering novel physical phenomena and functionalities. Understanding their complex behavior, especially in exchange coupled systems, is essential for advancing spintronics. Structures hybridizing topological insulators (TIs) with ferromagnetism are particularly promising for exploiting correlated interactions originated from the electrostatic and quantum mechanical nature of the exchange coupling. Owing to time-reversal symmetry breaking, exchange gap opens in the Dirac surface states of TI, enabling dissipationless chiral transport with full spin polarization. The unique spin-momentum locking feature of the surface Dirac fermions also bode well for unprecedented magnetoelectric properties in hybrid structures for tuning the magnetism via electrostatic means.}

_{Prof. Jagadeesh Moodera}

6

_{Correlated magnetic phenomena in quantum materials}

_{Minyong Ha}

_{Graduate Student}

_{Coexistence of dirac electrons and magnetism in Fe-based kagome metals. 
Spin-orbit coupled Dirac electronic states in topological insulators have shown significant promise as a source of spin currents including enabling efficient magnetization switching when interfaced with a ferromagnet. We discuss the diverse set of behaviors in the Fe-based kagome lattice which allows Dirac electrons and room temperature magnetism to coexist in a single material platform. The ferromagnetic kagome metal Fe3Sn2 hosts a gapped Dirac band in the bulk and spin-polarized dissipationless current circulating at its boundaries, transporting high fidelity spin information with zero power consumption. Alternatively, the antiferromagnetic kagome metal FeSn, consisting of an alternating stack of magnetic Fe-layer and heavy mass Sn-layer offers a natural atomic scale heterostructure that can be integrated into antiferromagnetic spintronic devices.}

 _{Prof. Joe Checkelsky}

7

_{Materials for energy efficient computing}

_{Angela Whitman}

_{Post Doc}

_{Antiferromagnetic spintronics for memory technology
The development of charge-based devices is fast approaching its limits according to Moore's law-driven International Technology Roadmap for Semiconductors. Spintronics is among the most frequently mentioned alternatives. The pressing task of improving performances has recently led to a growing interest in alternative magnetically ordered systems such as antiferromagnets (AFMs), as they offer the prospect of non-volatility and radiation hardness on a nanoscale combined with ultrafast spin-dynamics in the THz frequency range. The breakthrough in this field was the recent realization of electrical control of the Néel-vector revealing the high potential of AFMs for application in memory technology.}

_{Prof. Geoffrey Beach}

8

_{Materials for energy efficient computing}

_{Kai Litzius}

_{Post Doc}

_{Strengths and limitations of thin film ferrimagnetic bubble skyrmions
Magnetic skyrmions are nanoscale magnetic quasi-particles whose spin structure can be mapped continuously on a sphere. They are promising candidates for future spintronic devices such as the skyrmion racetrack memory and can be readily stabilized in interfacial thin film materials, which may exhibit efficient spin dynamics, making these systems extremely promising for applications. Here, we will discuss recent advances in the field of skyrmionics and how the performance of skyrmion-based devices may be enhanced by ferrimagnetic and antiferromagnetic materials. Furthermore, we will present our recent findings on strengths and limitations of skyrmionic applications and the predictability of their performances.}

_{Prof. Geoffrey Beach}