1] Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, California 94720, USA [2] Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, 12116 Praha 2, Czech Republic [3] Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic.
1] Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra E-08193, Spain [2] Max Planck Institute of Microstructure Physics, Weinberg 2, Halle D-06120, Germany.
Nat Mater. 2014 Apr;13(4):367-74. doi: 10.1038/nmat3861. Epub 2014 Jan 26.
The bistability of ordered spin states in ferromagnets provides the basis for magnetic memory functionality. The latest generation of magnetic random access memories rely on an efficient approach in which magnetic fields are replaced by electrical means for writing and reading the information in ferromagnets. This concept may eventually reduce the sensitivity of ferromagnets to magnetic field perturbations to being a weakness for data retention and the ferromagnetic stray fields to an obstacle for high-density memory integration. Here we report a room-temperature bistable antiferromagnetic (AFM) memory that produces negligible stray fields and is insensitive to strong magnetic fields. We use a resistor made of a FeRh AFM, which orders ferromagnetically roughly 100 K above room temperature, and therefore allows us to set different collective directions for the Fe moments by applied magnetic field. On cooling to room temperature, AFM order sets in with the direction of the AFM moments predetermined by the field and moment direction in the high-temperature ferromagnetic state. For electrical reading, we use an AFM analogue of the anisotropic magnetoresistance. Our microscopic theory modelling confirms that this archetypical spintronic effect, discovered more than 150 years ago in ferromagnets, is also present in AFMs. Our work demonstrates the feasibility of fabricating room-temperature spintronic memories with AFMs, which in turn expands the base of available magnetic materials for devices with properties that cannot be achieved with ferromagnets.
铁磁体中有序自旋态的双稳性为磁记忆功能提供了基础。最新一代的磁性随机存取存储器依赖于一种有效的方法，即用电子手段取代磁场来写入和读取铁磁体中的信息。这一概念最终可能会降低铁磁体对磁场干扰的敏感性，使其成为数据保持的弱点，而铁磁体的杂散场则成为高密度存储集成的障碍。在这里，我们报告了一种室温下双稳反铁磁（AFM）存储器，它产生的杂散场可以忽略不计，并且对强磁场不敏感。我们使用了一种由 FeRh AFM 制成的电阻器，它在室温以上约 100 K 时表现出铁磁性，因此允许我们通过施加磁场来设定 Fe 原子磁矩的不同集体方向。在冷却到室温时，AFM 序通过在高温铁磁状态下磁场和磁矩方向来确定 AFM 磁矩的方向。为了进行电读取，我们使用了 AFM 各向异性磁电阻的模拟。我们的微观理论模型证实，这个在 150 多年前在铁磁体中发现的典型的自旋电子效应，也存在于 AFM 中。我们的工作证明了用 AFM 制造室温自旋电子存储器的可行性，这反过来又扩展了具有铁磁体无法实现的特性的器件可用磁性材料的基础。
