Micro and nanostrips in spintronics: How to keep them cool

Abstract

This Tutorial explores the problem of Joule heating on metallic micro or nanostrips, still one of the most popular geometries in modern spintronics. Many of the effects that result from the interaction of a spin polarized current and the local magnetization require a sizeable current density. This implies, quite often, an unignorable Joule heating. Despite the few articles devoted to some aspects of Joule heating, there is still disinformation and many misconceptions on this topic, which is key for the correct interpretation of the scientific results. In this Tutorial, we highlight the material parameters that are important to keep the temperature of the strip under control and those that give only a marginal advantage. In the vast majority of papers, at least one of these parameters is missing. We also focus on some misconceptions, such as the belief that performing the measurement on a cryostat rules Joule heating out. In fact, for a fixed current density, measuring in a cryostat decreases the temperature but not enough to justify the use of such a costly measuring setup. At the practical level, we put forward a 1D model to calculate, in few seconds, if Joule heating is present and if it should be taken into account when interpreting the results. Finally, and importantly, we describe a simple fabrication route to enhance the dissipation of heat in the strip considerably. This fabrication strategy is more effective at keeping the temperature under control than performing the experiment at cryogenic temperatures.