Ultra-high frequency tunability in low-current and low-field spin-torque oscillators based on perpendicular magnetic tunnel junctions
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
We demonstrate ultra-high frequency tunability of up to 4.4 GHz/mA, and low threshold currents of about -21 $\mu$A, in spin-torque oscillators based on CoFeB/MgO/CoFeB magnetic tunnel junctions, in which both free and fixed layers have perpendicular magnetic anisotropy (PMA). By using different thicknesses of the two CoFeB layers, their individual PMA strengths can be tailored to achieve significant relative misalignment of their respective magnetizations in moderate in-plane fields. We observe a broad maximum in both the device resistance and the generated microwave power around maximum misalignment. Maximum frequency tunability is observed at low-to-moderate fields and decrease rapidly after maximum misalignment.
spin-torque oscillator, magnetic tunnel junction, magnetic perpendicular anisotropy
Research subject Materials Science and Engineering; Physics
IdentifiersURN: urn:nbn:se:kth:diva-191278OAI: oai:DiVA.org:kth-191278DiVA: diva2:955791
FunderSwedish Foundation for Strategic Research Swedish Research CouncilKnut and Alice Wallenberg Foundation
QC 201608292016-08-262016-08-262016-08-29Bibliographically approved