APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session S56: Spin Torques and Magnetoresistance
8:00 AM–11:00 AM,
Thursday, March 9, 2023
Room: Room 304
Sponsoring
Unit:
GMAG
Chair: Changjiang Liu, University at Buffalo
Abstract: S56.00008 : Spin-orbit Torques in Magnetron-Sputtered MoTe2*
9:48 AM–10:00 AM
Abstract
Presenter:
Shuchen Li
(University of Illinois at Urbana-Champaign)
Author:
Shuchen Li
(University of Illinois at Urbana-Champaign)
Weyl semimetals can generate large current-induced spin-orbit torques (SOT) that can manipulate the magnetization dynamics in the ferromagnetic materials, and thus play an important role in spintronic devices. Due to their concomitant reduced symmetries, Weyl semimetals are also promising for generating SOTs with novel symmetries that may be able to switch perpendicular magnetic anisotropy thin films. Large spin-orbit torque efficiencies have already been reported for exfoliated and sputtered WTe2 films [1]. Recently, the Td phase MoTe2, which is Weyl semimetal, has attracted a lot of attentions in the field of spintronics, due to its theoretically predicted SOT efficiencies that are even larger than those of WTe2 [2]. Here, we studied the effects of processing conditions on the stoichiometry and crystal structure of the magnetron-sputtered MoTe2 films by using Rutherford backscattering and X-ray diffraction. Furthermore, we identified different phases of the sputtered MoTe2 thin films using Raman spectroscopy, and we have observed a stable Td semimetal phase even at room temperature. The Td phase is generally considered to be a low-temperature phase and only appears at temperatures below 250 K, and at room temperatures, MoTe2 will be in the 1T’ monoclinic phase or the 2H hexagonal phase [3]. We have also observed dimensionality-dependent phase transitions from the Td to the 1T’ phase at room temperature for sputtered MoTe2 thin films as the characteristic peak for the Td phase MoTe2 gradually shifts from 264 cm-1 to 259 cm-1, the Raman peak position for the 1T’ phase, as the thickness of the sputtered films increases. Finally, SOT efficiencies of the MoTe2 thin films were measured via spin-torque ferromagnetic resonance on MoTe2/Ni80Fe20 heterostructures and we observed a large novel SOT due to the spins with out-of-plane polarization directions in both the symmetric and anti-symmetric components of the homodyne mixing voltage signals. The efficiencies of the damping-like SOTs and the field-like SOTs generated by spins polarized out-of-plane are estimated to be 16% and 27%, respectively.
*NSF