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Continuous-Film vs. Device-Level Ferromagnetic Resonance in Magnetic Tunnel Junction Thin Films



Eric R. Evarts, Matthew R. Pufall, William H. Rippard


We quantitatively compare film-level ferromagnetic resonance (FMR) measurements to device-level FMR measurements on magnetic tunnel junction (MTJ) thin films with in-plane magnetization using both thermal FMR (T-FMR) and field-swept spin torque FMR measurements (FS-ST-FMR). The film-level and FS-ST-FMR device-level determination of damping, α, are in agreement, but the T-FMR α is lower than the others. The device-level effective magnetization (Mdeff) is lower than film-level measurements due to the demagnetizing field of the patterned free layer and M(deff) shows device-to-device variations due to a combination of size variation and explicit measurement of local film variations. At the device level, the inhomogeneous broadening ({Δ}H0) is nearly zero while in film-level measurements υ0{Δ}H0 > 10 mT due to averaging the local film variations detected explicitly in Meff at the device level. These results suggest that continuous-film and FS-ST-FMR measurements can provide the same information about thin film Meff, α, and {Δ}H0 with minimal interpretation, but caution is necessary when using T-FMR to determine α.
Physical Review B


ferromagnetic resonance, magnetic tunnel junction, MgO


Evarts, E. , Pufall, M. and Rippard, W. (2013), Continuous-Film vs. Device-Level Ferromagnetic Resonance in Magnetic Tunnel Junction Thin Films, Physical Review B, [online], (Accessed June 20, 2024)


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Created February 25, 2013, Updated November 10, 2018