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Grenoble, France

Prejbeanu I.L.,Crocus Technology | Bandiera S.,Crocus Technology | Alvarez-Herault J.,Crocus Technology | Sousa R.C.,SPINTEC | And 2 more authors.
Journal of Physics D: Applied Physics | Year: 2013

This paper is focused on thermally assisted magnetic random access memories (TA-MRAMs). It explains how the heating produced by Joule dissipation around the tunnel barrier of magnetic tunnel junctions (MTJs) can be used advantageously to assist writing in MRAMs. The main idea is to apply a heating pulse to the junction simultaneously with a magnetic field (field-induced thermally assisted (TA) switching). Since the heating current also provides a spin-transfer torque (current-induced TA switching), the magnetic field lines can be removed to increase the storage density of TA-MRAMs. Ultimately, thermally induced anisotropy reorientation (TIAR)-assisted spin-transfer torque switching can be used in MTJs with perpendicular magnetic anisotropy to obtain ultimate downsize scalability with reduced power consumption. TA writing allows extending the downsize scalability of MRAMs as it does in hard disk drive technology, but it also allows introducing new functionalities particularly useful for security applications (Match-in-Place™ technology). © 2013 IOP Publishing Ltd.

Bandiera S.,SPINTEC | Sousa R.R.,SPINTEC | Rodmacq B.B.,SPINTEC | Dieny B.,SPINTEC
IEEE Magnetics Letters | Year: 2011

An asymmetry in the interfacial anisotropies of Pt/Co and Co/Pt interfaces was observed in Pt/Co/Pt sputtered trilayers, the interfacial anisotropy arising from the bottom Pt/Co interface being significantly higher than that from the top Co/Pt one. Interdiffusion at the top interface is believed to be the main factor for this asymmetry. It dramatically decreases the anisotropy of the stack when the cobalt layer is thinner than 1 nm. By introducing ultrathin layers of materials immiscible with Co and acting as a diffusion barrier at the Co/Pt interface, the effective anisotropy can be doubled in this low Co thickness range. This is of great interest for spintronic devices, particularly for out-of-plane magnetized magnetoresistive random access memory structures that require high perpendicular magnetic anisotropy when their lateral dimensions are reduced below 45 nm. © 2010 IEEE.

Mikuszeit N.,SPINTEC | Boulle O.,SPINTEC | Buda-Prejbeanu L.,SPINTEC | Mihai M.I.,SPINTEC | Gaudin G.,SPINTEC
2015 IEEE International Magnetics Conference, INTERMAG 2015 | Year: 2015

The discovery that the magnetization of a perpendicularly magnetized nanomagnet can be reversed by an in-plane current via spin orbit torque (SOT) has opened a new way to manipulate magnetization at the nanoscale1. This novel switching mechanism has led to a concept of non-volatile magnetic memory MRAM, namely the SOT-MRAM, which combines low power, fast switching, reliability and large endurance2. Although numerous experimental works were devoted to the study of magnetization switching by SOT, the mechanism of the magnetization reversal induced by SOT is poorly understood. Magnetization switching experiments were first interpreted in terms of a macrospin model3, but although a qualitative agreement could be achieved, the predicted switching current densities were very high compared to the experimental ones3-5. On the contrary, recent experimental works suggested that the magnetization during the switching is inhomogeneous and that switching occurs by domain nucleation followed by domain wall propagation6,7. However, the switching mechanisms were not elucidated. Here we present the results of micromagnetic simulations and analytical modelling which shed a new light on the magnetization reversal in the presence of SOT. We show that the Dzyaloshinskii-Moriya interaction (DMI) plays a key role in the reversal process by leading to a deterministic domain nucleation on the edge of the nanomagnet which triggers the reversal. A simple analytical model, taking into account the magnetization tilting on the edge due to the DMI, allows to calculate the switching current, which is the current for domain nucleation on the edge. Our model provides a much better agreement with experimental results compared to the macrospin approach. © 2015 IEEE.

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