Browsing by Author "Amin, Vivek P."

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    Large Exotic Spin Torques in Antiferromagnetic Iron Rhodium
    (APS, 2022-08) Gibbons, Jonathan; Dohi, Takaaki; Amin, Vivek P.; Xue, Fei; Ren, Haowen; Xu, Jun-Wen; Arava, Hanu; Shim, Soho; Saglam, Hilal; Liu, Yuzi; Pearson, John E.; Mason, Nadya; Petford-Long, Amanda K.; Haney, Paul M.; Stiles, Mark D.; Fullerton, Eric E.; Kent, Andrew D.; Fukami, Shunsuke; Hoffman, Axel; Physics, School of Science
    Spin torque is a promising tool for driving magnetization dynamics for computing technologies. These torques can be easily produced by spin-orbit effects, but for most conventional spin source materials, a high degree of crystal symmetry limits the geometry of the spin torques produced. Magnetic ordering is one way to reduce the symmetry of a material and allow exotic torques, and antiferromagnets are particularly promising because they are robust against external fields. We present spin torque ferromagnetic resonance (ST-FMR) measurements and second harmonic Hall measurements characterizing the spin torques in antiferromagnetic iron rhodium alloy. We report extremely large, strongly temperature-dependent exotic spin torques with a geometry apparently defined by the magnetic ordering direction. We find the spin torque efficiency of iron rhodium to be (207 ± 94)% at 170 K and (88 ± 32)% at room temperature. We support our conclusions with theoretical calculations showing how the antiferromagnetic ordering in iron rhodium gives rise to such exotic torques.
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    Phase-resolved electrical detection of coherently coupled magnonic devices
    (AIP, 2021-05) Li, Yi; Zhao, Chenbo; Amin, Vivek P.; Zhang, Zhizhi; Vogel, Michael; Xiong, Yuzan; Sklenar, Joseph; Divan, Ralu; Pearson, John; Stiles, Mark D.; Zhang, Wei; Hoffmann, Axel; Novosad, Valentyn; Physics, School of Science
    We demonstrate the electrical detection of magnon–magnon hybrid dynamics in yttrium iron garnet/Permalloy (YIG/Py) thin film bilayer devices. Direct microwave current injection through the conductive Py layer excites the hybrid dynamics consisting of the uniform mode of Py and the first standing spin wave (n = 1) mode of YIG, which are coupled via interfacial exchange. Both the two hybrid modes, with Py- or YIG-dominated excitations, can be detected via the spin rectification signals from the conductive Py layer, providing phase resolution of the coupled dynamics. The phase characterization is also applied to a nonlocally excited Py device, revealing the additional phase shift due to the perpendicular Oersted field. Our results provide a device platform for exploring hybrid magnonic dynamics and probing their phases, which are crucial for implementing coherent information processing with magnon excitations.
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    Self-induced inverse spin Hall effect in La0.67⁢Sr0.33⁢MnO3 films
    (APS, 2024-01) Gupta, Pushpendra; Park, In Jun; Swain, Anupama; Mishra, Abhisek; Amin, Vivek P.; Bedanta, Subhankar; Physics, School of Science
    The efficient generation of spin currents and spin torques via spin-orbit coupling is an important goal of spintronics research. One crucial metric for spin current generation is the spin Hall angle, which is the ratio of the spin Hall current to the transversely flowing charge current. A typical approach to measure the spin Hall angle in nonmagnetic materials is to generate spin currents via spin pumping in an adjacent ferromagnetic layer and measure the transverse voltage from the inverse spin Hall effect in the nonmagnetic layer. However, given that the spin Hall effect also occurs in ferromagnets, single ferromagnetic layers could generate a self-induced transverse voltage during spin pumping as well. Here we show that manganite-based La0.67⁢Sr0.33⁢MnO3 (LSMO) films deposited by pulsed laser deposition exhibit a significant self-induced inverse spin Hall voltage while undergoing spin pumping. A spin pumping voltage of 1.86µ⁢V is observed in the LSMO (12 nm) film. Using density functional theory and the Kubo formalism, we calculate the intrinsic spin current conductivities of these films and show that they are in reasonable agreement with the experimental measurements.
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    Suppression of spin pumping at metal interfaces
    (AIP, 2023-10) Lim, Youngmin; Nepal, Bhuwan; Smith, David A.; Wu, Shuang; Srivastava, Abhishek; Nakarmi, Prabandha; Mewes, Claudia; Jiang, Zijian; Gupta, Adbhut; Viehland, Dwight D.; Klewe, Christoph; Shafer, Padraic; Park, In Jun; Mabe, Timothy; Amin, Vivek P.; Heremans, Jean J.; Mewes, Tim; Emori, Satoru; Physics, School of Science
    An electrically conductive metal typically transmits or absorbs a spin current. Here, we report on evidence that interfacing two metal thin films can suppress spin transmission and absorption. We examine spin pumping in spin-source/spacer/spin-sink heterostructures, where the spacer consists of metallic Cu and Cr thin films. The Cu/Cr spacer largely suppresses spin pumping—i.e., neither transmitting nor absorbing a significant amount of spin current—even though Cu or Cr alone transmits a sizable spin current. The antiferromagnetism of Cr is not essential for the suppression of spin pumping, as we observe similar suppression with Cu/V spacers with V as a nonmagnetic analog of Cr. We speculate that diverse combinations of spin-transparent metals may form interfaces that suppress spin pumping, although the underlying mechanism remains unclear. Our work may stimulate a new perspective on spin transport in metallic multilayers.