Electrical switching of an antiferromagnet

  • Wadley P
  • Howells B
  • Železný J
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Abstract

In charge-based information devices, perturbations such as ionizing radiation can lead to data loss. In contrast, spin-based devices, in which different magnetic moment orienta-tions in a ferromagnet (FM) represent the zeros and ones (1), are robust against charge perturbations. However, the FM moments can be unintentionally reoriented and the da-ta erased by perturbing magnetic fields generated externally or internally within the memory circuitry. If magnetic memories were based on antiferromagnets (AFMs) instead, they would be robust against charge and magnetic field per-turbations. Additional advantages of AFMs compared to FMs include the invisibility of data stored in AFMs to exter-nal magnetic probes, ultrafast spin dynamics in AFMs, and the broad range of metal, semiconductor, or insulator mate-rials with room-temperature AFM order (2–7). The energy barrier separating stable orientations of or-dered spins is due to the magnetic anisotropy energy. It is an even function of the magnetic moment which implies that the magnetic anisotropy and the corresponding memory functionality are readily present in both FMs and AFMs (8, 9). The magneto-transport counterpart of the magnetic anisotropy energy is the anisotropic magnetore-sistance (AMR). In the early 1990's, the first generation of FM MRAM micro-devices used AMR for the electrical read-out of the memory state (10). AMR is an even function of the magnetic moment which again implies its presence in AFMs (11). Although AMR in AFMs was experimentally confirmed in several recent studies (12–17), efficient means for manipu-lating AFM moments have remained elusive. It has been proposed that current-induced spin transfer torques of the form / ~ () dM dt M M p × × , which are used for electrical writing in the most advanced FM magnetic random access memories (MRAMs) (1), could also produce large angle reorientation of the AFM moments (18). In these antidamping-like torques, M is the magnetic moment vec-tor and p is the electrically injected carrier spin-polarization. Translated to AFMs, the effective field propor-tional to

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Authors

  • P Wadley

  • B Howells

  • J Železný

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