IEEE MAGNETICS SOCIETY SECTION Received 27 September 2023, accepted 17 October 2023, date of publication 20 October 2023, date of current version 27 October 2023. Digital Object Identifier 10.1109/ACCESS.2023.3326448 Antiferromagnetic Films and Their Applications ATSUFUMI HIROHATA 1,2 , (Senior Member, IEEE), DAVID C. LLOYD 1 , TAKAHIDE KUBOTA 3 , (Member, IEEE), TAKESHI SEKI 4 , KOKI TAKANASHI 2,4,5 , (Senior Member, IEEE), HIROAKI SUKEGAWA 6 , (Member, IEEE), ZHENCHAO WEN 6 , SEIJI MITANI 6,7 , AND HIROKI KOIZUMI 2 1 School of Physics, Engineering and Technology, University of York, YO10 5DD York, U.K. 2 Center for Science and Innovation in Spintronics, Core Research Cluster, Tohoku University, Sendai 980-8579, Japan 3 Advanced Spintronics Medical Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-0845, Japan 4 Institute for Materials Research, Tohoku University, Sendai 980-8579, Japan 5 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan 6 Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba 305-0047, Japan 7 Graduate School of Science and Technology, University of Tsukuba, Tsukuba 305-8577, Japan Corresponding author: Atsufumi Hirohata (atsufumi.hirohata@york.ac.uk) This work was supported in part by EU-FP7 Heusler Alloy Replacement for Iridium (HARFIR) under Grant NMP3-SL-2013-604398; in part by the Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/K03278X/1, Grant EP/M02458X/1, and Grant EP/V007211/1; in part by the Japan Science and Technology Agency (JST) Core Research for Evolutional Science and Technology (CREST) under Grant JPMJCR17J5; and in part by the Global Institute for Materials Research Tohoku (GIMRT) of Tohoku University and Ministry of Education, Culture, Sports, Science and Technology (MEXT) Initiative to Establish Next-Generation Novel Integrated Circuits Centers (X-NICS) under Grant JPJ011438. ABSTRACT Spintronic devices are expected to replace the recent nanoelectronic memories and sensors due to their effciency in energy consumption and functionality with scalability. To date, spintronic devices, namely magnetoresistive junctions, employ ferromagnetic materials by storing information bits as their magnetization directions. However, in order to achieve further miniaturization with maintaining and/or improving their effciency and functionality, new materials development is required: 1) increase in spin polarization of a ferromagnet or 2) replacement of a ferromagnet by an antiferromagnet. Antiferromagnetic materials have been used to induce an exchange bias to the neighboring ferromagnet but they have recently been found to demonstrate a 100% spin-polarized electrical current, up to THz oscillation and topological effects. In this review, the recent development of three types of antiferromagnets is summarized with offering their future perspectives towards device applications. INDEX TERMS Antiferromagnetic materials, Hall effect, magnetoresistance, spintronics, spin polarized transport. I. INTRODUCTION Spintronics is one of the emerging felds in condensed matter physics in the view of replacing the recent nanoelec- tronic devices by improving their effciency and functionality [1], [2]. In spintronic devices, further improvements are required to continue miniaturization to be comparable with the Si-based semiconductor technology. With a ferromagnet (FM), the miniaturization may induce edge domains and cross-talk between junctions via stray felds, which may pre- vent fast and reliable operation. On the other hand, using an antiferromagnet (AF), these obstacles can be avoided. The associate editor coordinating the review of this manuscript and approving it for publication was Montserrat Rivas. Namely for the reduction in power consumption, highly eff- cient generation and detection of a spin-polarized electrical current need to be developed using the spin-orbit torque, spin caloritronic and topological effects. AF materials and their properties were initially investigated by Néel [3] and have been utilized to exchange couple with the neighboring FM magnetization [4]. This can be measured as a shift in the corresponding magnetization curve as known as an exchange bias (EB) feld H ex . H ex has been used to pin one of the FM magnetizations in a FM/non-magnet (NM)/FM trilayer, i.e., a spin-valve structure [5]. This is a basic structure for a read head of a hard disk drive (HDD). By replacing the NM layer with an insulating barrier, a magnetic tunnel junction (MTJ) has been fabricated in a similar manner, which has VOLUME 11, 2023  2023 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/ 117443