The discovery that a current flowing in a heavy metal can exert a torque on a neighboring ferromagnet has opened a new way to manipulate the magnetization at the nanoscale. This “spin orbit torque” (SOT) has been demonstrated in ultrathin magnetic multilayers with structural inversion asymmetry (SIA) and high spin orbit coupling, such as Pt/Co/AlOx multilayers. We have shown that this torque can lead to the magnetization switching of a perpendicularly magnetized nanomagnet by an in-plane current injection. The manipulation of magnetization by SOT has led to a novel concept of magnetic RAM memory, the SOT-MRAM, which combines non volatility, high speed, reliability and large endurance. These features make the SOT-MRAM a good candidate to replace SRAM for non-volatile cache memory application.
We will present the proof of concept of a perpendicular SOT-MRAM cell composed of a Ta/FeCoB/MgO/FeCoB magnetic tunnel junction and demonstrate ultra-fast (down to 300 ps) deterministic bipolar magnetization switching. Macrospin and micromagnetic simulations including SOT cannot reproduce the experimental results, which suggests that additional physical mechanisms are at stacks. Our results show that SOT-MRAM is fast, reliable and low power, which is promising for non-volatile cache memory application. We will also discuss recent experiments of magnetization reversal in ultrathin multilayers Pt/Co/AlOx by very short (<200 ps) current pulses. We will show that in this material, the Dzyaloshinskii-Moryia interaction plays a key role in the reversal process.
Olivier Boulle, Murat Cubukcu, Claire Hamelin, Nathalie Lamard, Liliana Buda-Prejbeanu, Nikolai Mikuszeit, Kevin Garello, Pietro Gambardella, Juergen Langer, Berthold Ocker, Mihai Miron, and Gilles Gaudin, "Ultra-fast three terminal perpendicular spin-orbit torque MRAM (Presentation Recording)," Proc. SPIE 9551, Spintronics VIII, 955103 (Presented at SPIE Nanoscience + Engineering: August 09, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2189096.4519370525001.
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