Making magnets flip like cats at room temperature
In today’s world of ever-increasing digital information storage an
d computation, the next information storage revolution seeks to exploit a novel effect arising from the relativistic physics of Einstein, which allows to effectively convert a new type of magnet into cats. Through this effect, these magnets can flip themselves through the internal motion of their own electrons. One can almost describe these new types of magnets as relativistic magnetic cats.
In these new magnetic materials, a current running through the magnet can flip the direction of the magnetization depending on the direction of the current. This novel phenomenon in physics, dubbed spin-orbit torques, links the spin-degree of freedom of magnets that gives rise to the magnetization, to the charge degree of freedom that allows for current-charge motion inside the material.
This novel effect has been pioneered, among others, by recent predictions by the Sinova group in Mainz together with theoretical and experimental collaborators. The effect occurs in magnetic materials that have broken-inversion symmetry. They first observed this in the artificial bulk diluted magnetic semiconductor GaMnAs (read more). GaMnAs is the diluted counterpart of crystalline zincblende structures of Silicon and Gallium arsenide, which are the pillars of modern electronics. However, in GaMnAs, spin-orbit torques were demonstrated only at very low temperatures.
Now Prof. Sinova with his students Jacob Gayles and Libor Smejkal in collaboration with an international team of researchers from Prague, Cambridge, Würzburg, Jülich and Nottingham, have published their findings, which could pave the way for using spin-orbit torques in technological applications. Thanks to this synergetic teamwork of theorists and experimentalists, the authors were able to predict and demonstrate the effect of spin-orbit torques in NiMnSb crystal at room temperature. NiMnSb was chosen according to the systematic analysis of the symmetry the crystal point groups in conjunction with microscopic first principles calculations of the effect. All electrical ferromagnetic resonance measurements were then used to detect the room temperature spin-orbit torques in NiMnSb microbars. Being able to use single magnet manipulation at room temperature represents an important step towards improved magnetic random access memory architectures for technical applications that are all fully electrical, highly scalable, and require low power.
Read the original publication in the prestigious Nature Physics journal.