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Experimental Study of the Variation in Oscillation Characteristics of Point-Contact-Based Spin-Torque Oscillators

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2 Author(s)
Shingo Tamaru ; Electrical and Computer Engineering Department, Carnegie Mellon University, Pittsburgh, PA, USA ; David S. Ricketts

This paper presents an experimental study of the variation in oscillation characteristics of circular point-contact-based spin-torque oscillators (PC-STOs). We first measured the oscillation behavior of multiple, identically fabricated PC-STOs, then made the same measurements on a PC-STO and rotated the azimuth angle of the bias field \varphi . Our results show considerable device-to-device variations among identical PC-STOs. More striking is large changes within a single PC-STO for a small \varphi rotation, which is totally inconsistent with the geometrical symmetry of the device. These results suggest that the giant magnetoresistance stack has some form of microstructural inhomogeneity, which causes a strong \varphi dependence of the oscillation behavior, eventually resulting in the device-to-device variation. Some possible sources of the inhomogeneity are discussed based on these observation results.

Published in:

IEEE Magnetics Letters  (Volume:3 )