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arXiv · 1603.02591

Spin-wave thermal population as temperature probe in Magnetic Tunnel Junctions

Adrien Le Goff·Vladimir Nikitin·Thibaut Devolder
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Abstract

We study whether a direct measurement of the absolute temperature of a Magnetic Tunnel Junction (MTJ) can be performed using the high frequency electrical noise that it delivers under a finite voltage bias. Our method includes quasi-static hysteresis loop measurements of the MTJ, together with the field-dependence of its spin wave noise spectra. We rely on an analytical modeling of the spectra by assuming independent fluctuations of the different sub-systems of the tunnel junction that are described as macrospin fluctuators. We illustrate our method on perpendicularly magnetized MgO-based MTJs patterned in 50*100 nm2 nanopillars. We apply hard axis (in-plane) fields to let the magnetic thermal fluctuations yield finite conductance fluctuations of the MTJ. Instead of the free layer fluctuations that are observed to be affected by both spin-torque and temperature, we use the magnetization fluctuations of the sole reference layers. Their much stronger anisotropy and their much heavier damping render them essentially immune to spin-torque. We illustrate our method by determining current-induced heating of the perpendicularly magnetized tunnel junction at voltages similar to those used in spin-torque memory applications. The absolute temperature can be deduced with a precision of +/- 60 K and we can exclude any substantial heating at the spin-torque switching voltage.

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Adrien Le Goff, Vladimir Nikitin, Thibaut Devolder. 2016-03-08. Spin-wave thermal population as temperature probe in Magnetic Tunnel Junctions. https://doi.org/10.1063/1.4953680

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