Room-temperature antiferromagnetic memory resistor

摘要

The bistability of ordered spin states in ferromagnets (FMs) provides themagnetic memory functionality. Traditionally, the macroscopic moment of orderedspins in FMs is utilized to write information on magnetic media by a weakexternal magnetic field, and the FM stray field is used for reading. However,the latest generation of magnetic random access memories demonstrates a newefficient approach in which magnetic fields are replaced by electrical meansfor reading and writing. This concept may eventually leave the sensitivity ofFMs to magnetic fields as a mere weakness for retention and the FM stray fieldsas a mere obstacle for high-density memory integration. In this paper we reporta room-temperature bistable antiferromagnetic (AFM) memory which producesnegligible stray fields and is inert in strong magnetic fields. We use aresistor made of an FeRh AFM whose transition to a FM order 100 degrees aboveroom-temperature, allows us to magnetically set different collective directionsof Fe moments. Upon cooling to room-temperature, the AFM order sets in with thedirection the AFM moments pre-determined by the field and moment direction inthe high temperature FM state. For electrical reading, we use anantiferromagnetic analogue of the anisotropic magnetoresistance (AMR). Wereport microscopic theory modeling which confirms that this archetypicalspintronic effect discovered more than 150 years ago in FMs, can be equallypresent in AFMs. Our work demonstrates the feasibility to realizeroom-temperature spintronic memories with AFMs which greatly expands themagnetic materials base for these devices and offers properties which areunparalleled in FMs.