arXiv subjects

Joseph Finley

Publications and source records attributed to Joseph Finley.

6 recordsLinked to original sources

arXiv2022

Coherent magnon-induced domain wall motion in a magnetic insulator channel

Advancing the development of spin-wave devices requires high-quality low-damping magnetic materials where magnon spin currents can propagate efficiently and interact effectively with local magnetic textures. We show that magnetic domain walls (DW) can modulate spin-wave transport in perpendicularly magnetized channels of Bi-doped yttrium-iron-garnet (BiYIG). Conversely, we demonstrate that the magnon spin current can drive DW motion in the BiYIG channel device by means of magnon spin-transfer torque. The DW can be reliably moved over 15 um distances at zero applied magnetic field by a magnon spin current excited by an RF pulse as short as 1 ns. The required energy for driving DW motion is orders of magnitude smaller than those reported for metallic systems. These results facilitate low-switching-energy magnonic devices and circuits where magnetic domains can be efficiently reconfigured by magnon spin currents flowing within magnetic channels.

cond-mat.mes-hall↗

arXiv2020

Manipulation of coupling and magnon transport in magnetic metal-insulator hybrid structures

Ferromagnetic metals and insulators are widely used for generation, control and detection of magnon spin signals. Most magnonic structures are based primarily on either magnetic insulators or ferromagnetic metals, while heterostructures integrating both of them are less explored. Here, by introducing a Pt/yttrium iron garnet (YIG)/permalloy (Py) hybrid structure grown on Si substrate, we studied the magnetic coupling and magnon transmission across the interface of the two magnetic layers. We found that within this structure, Py and YIG exhibit an antiferromagnetic coupling field as strong as 150 mT, as evidenced by both the vibrating-sample magnetometry and polarized neutron reflectometry measurements. By controlling individual layer thicknesses and external fields, we realize parallel and antiparallel magnetization configurations, which are further utilized to control the magnon current transmission. We show that a magnon spin valve with an ON/OFF ratio of ~130% can be realized out of this multilayer structure at room temperature through both spin pumping and spin Seebeck effect experiments. Thanks to the efficient control of magnon current and the compatibility with Si technology, the Pt/YIG/Py hybrid structure could potentially find applications in magnon-based logic and memory devices.

cond-mat.mtrl-sci↗

arXiv2019

Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film

Quantitative investigation on the current-induced torque in antiferromagnets represents a great challenge, due to the lack of an independent method for controlling Néel vectors. Here by utilizing an antiferromagnetic insulator with Dzyaloshinskii-Moriya interaction, α-Fe2O3, we show that the Néel vector can be controlled with a moderate external field, which is further utilized to calibrate the current-induced magnetic dynamics. We find that the current-induced magnetoresistance change in antiferromagnets can be complicated by resistive switching that does not have a magnetic origin. By excluding non-magnetic switching and comparing the current-induced dynamics with the field-induced one, we determine the nature and magnitude of current-induced effects in Pt/α-Fe2O3 bilayer films.

cond-mat.mes-hall↗

arXiv2019

Electrical manipulation of spin pumping signal through nonlocal thermal magnon transport

We study the magnon transport in the nonlocal configuration composed of two Pt strips on top of yttrium iron garnet, with and without the presence of RF microwave generated by an on-chip antenna. We find that the spin-Hall induced thermal magnon heating/cooling, the Oersted field as well as the Joule heating generated by the a.c. current in the Pt injector can significantly influence the spin-pumping signal measured by the Pt detector in the presence of RF microwave, forcing the spin-pumping voltage to show up in the first and second harmonic signals in the nonlocal magnon transport measurement. These results indicate that nonlocal magnon transport configuration can serve as a structure to electrically detect and manipulate the spin-pumping signal. Furthermore, certain caution is needed when studying the interplay between incoherent magnon and coherent magnon spin transport in the nonlocal transport configuration, since the change in microwave-induced spin-pumping voltage can overwhelm the incoherent magnon transport signals.

physics.app-ph↗

arXiv2017

Room temperature spin-orbit torque switching induced by a topological insulator

Recent studies on the magneto-transport properties of topological insulators (TI) have attracted great attention due to the rich spin-orbit physics and promising applications in spintronic devices. Particularly the strongly spin-moment coupled electronic states have been extensively pursued to realize efficient spin-orbit torque (SOT) switching. However, so far current-induced magnetic switching with TI has only been observed at cryogenic temperatures. It remains a controversial issue whether the topologically protected electronic states in TI could benefit spintronic applications at room temperature. In this work, we report full SOT switching in a TI/ferromagnet bilayer heterostructure with perpendicular magnetic anisotropy at room temperature. The low switching current density provides a definitive proof on the high SOT efficiency from TI. The effective spin Hall angle of TI is determined to be several times larger than commonly used heavy metals. Our results demonstrate the robustness of TI as an SOT switching material and provide a direct avenue towards applicable TI-based spintronic devices.

cond-mat.mtrl-sci↗

arXiv2016

Spin-Orbit Torque Efficiency in Compensated Ferrimagnetic Cobalt-Terbium Alloys

Despite the potential advantages of information storage in antiferromagnetically coupled materials, it remains unclear whether one can control the magnetic moment orientation efficiently because of the cancelled magnetic moment. Here, we report spin-orbit torque induced magnetization switching of ferrimagnetic Co1-xTbx films with perpendicular magnetic anisotropy. Current induced switching is demonstrated in all of the studied film compositions, including those near the magnetization compensation point. The spin-orbit torque induced effective field is further quantified in the domain wall motion regime. A divergent behavior that scales with the inverse of magnetic moment is confirmed close to the compensation point, which is consistent with angular momentum conservation. Moreover, we also quantify the Dzyaloshinskii-Moriya interaction energy in the Ta/Co1-xTbx system and we find that the energy density increases as a function of the Tb concentration. The demonstrated spin-orbit torque switching, in combination with the fast magnetic dynamics and minimal net magnetization of ferrimagnetic alloys, promises spintronic devices that are faster and with higher density than traditional ferromagnetic systems.

cond-mat.mtrl-sci↗