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Room-temperature antiferromagnetic memory resistor

Abstract

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.

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Figure 1: AFM-AMR memory functionality in a FeRh resistor.
Figure 2: Characterization of the magnetic and crystal structure of the FeRh film.
Figure 3: Magnetic properties.
Figure 4: Stability of the memory states at high magnetic fields.
Figure 5: Temperature dependence of the AMR.

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Acknowledgements

The authors acknowledge the support from the NSF (Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems, Cooperative Agreement Award EEC-1160504) and DOE. Transmission electron microscopy characterization was performed at NCEM, which is supported by the Office of Science, Office of Basic Energy Sciences of the US Department of Energy under Contract No. DE-AC02—05CH11231. J.F. acknowledges financial support from the Spanish Government (Projects MAT2011-29269-C03, CSD2007-00041) and Generalitat de Catalunya (2009 SGR 00376); C.F. acknowledges financial support from the Spanish Government (Projects MAT2012-33207, CSD2007-00041). I.F. acknowledges a Beatriu de Pinós postdoctoral scholarship (2011 BP-A 00220) and the Catalan Agency for Management of University and Research Grants (AGAUR-Generalitat de Catalunya). X.M. acknowledges the Grant Agency of the Czech Republic No. P204/11/P339. Research at the University of Nottingham was funded by EPSRC grant EP/K027808/1. T.J. acknowledges support from the ERC Advanced Grant 268066, Praemium Academiae of the Academy of Sciences of the Czech Republic, and from the Ministry of Education of the Czech Republic Grant LM2011026. S.S. acknowledges funding by STARnet FAME. J. Kuneš 83 and I.T. acknowledge the Czech Science Foundation No. P204/11/1228.

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Sample preparation, R.J.P., J.D.C., L.Y.; scanning transmission electron microscopy, C.T.N.; magnetotransport and structural characterization, I.F. and C.F.; data analysis, I.F., C.F., P.W., J-H.C. and D.Y.; X-ray linear dichroism, J.L., E.A. and Q.H.; theory, J. Kudrnovský, I.T. and J. Kuneš; writing and project planning, X.M., T.J., J.F., P.W., S.S. and R.R.

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Correspondence to X. Marti.

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Marti, X., Fina, I., Frontera, C. et al. Room-temperature antiferromagnetic memory resistor. Nature Mater 13, 367–374 (2014). https://doi.org/10.1038/nmat3861

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