Magnetic Information Storage in Antiferromagnet Spintronic Devices

Funding Institution: Fondazione Cariplo, grant 2013
People: Prof. Matteo Cantoni (Project leader)
Partners: CNR-SPIN (S. Picozzi, A. Stroppa)
Duration: 3 years (2014-2017)

Antiferromagnet (AFM) spintronics is an emerging branch of spin electronics aiming at exploiting the antiferromagnetic order, instead of the ferromagnetic (FM) one, in order to store information in memory cells. The absence of stray fields and the higher robustness versus external perturbations of AFMs, with respect to their FM counterparts, allow for larger packing density and higher reliability and durability, that are two key requisites for new generation memories. The project aims at exploring two kind of devices:

  • IrMn-based vertical devices, comprising an IrMn layer, a tunneling barrier (MgO) and a non-magnetic layer (Ta or Ru) forming a so-called AntiFerromagnetic Tunneling Junction (AFTJ). The information is stored in the IrMn spin alignment (parallel or perpendicular to the current flow in the device) by field cooling and read by anisotropic magnetoresistance (AMR). The main goal of the project is to realize such devices on Silicon platforms, looking for CMOS compatibility, and with operation temperature larger or equal than room temperature.
  • Cr-based planar devices, comprising a Cr or Cr2O3 film eventually capped by a thin Pt layer. The information is stored in the Cr spin alignment (with respect to the normal to the sample) by field cooling and read by anisotropic magneto resistance (AMR) and anomalous Hall effect (AHE). The main results obtained are:
    • 1.3% AMR below 125 K in a thin Cr film. This constitutes the first prototype on an AFM memory entirely based on Cr.
    • Magnetic proximity effects at the Cr/Pt and Cr2O3/Pt interfaces, resulting in a net magnetic moment induced by the AFM Cr and Cr2O3 in the Pt underlayer. A measurement system based on the detection of the anomalous Hall effect (AHE) in Pt has been appositely designed and realized in the framework of this project.
    • Synthesis of single-crystal-like Cr2O3 films from Cr layer, without the need of reactive gases;
    • Deposition of Cr and Cr2O3 films on ferroelectric BaTiO3 underlayers, in the search for the electric control of the spin state.

Moreover, ab-initio calculations and experiments addressed alternative ways of information writing (magneto-electric coupling), as well as novel materials (Mn2Au, GeTe, CuMnAs), in order to propose innovative strategies pathways to be followed and experimentally investigated.

Publications

  1. L. Baldrati, C. Rinaldi, A. Manuzzi, M. Asa, L. Aballe, M. Foerster, N. Biškup, M. Varela, M. Cantoni and R. Bertacco, “Electrical Switching of Magnetization in the Artificial Multiferroic CoFeB/BaTiO3”, Adv. Electronics Materials (2016)
  2. E. Plekhanov, A. Stroppa, and S. Picozzi, “Magneto-electric coupling in antiferromagnet/ferroelectric Mn2Au/BaTiO3 interface”, J. Appl. Phys. 120, 074104 (2016)
  3. C. Rinaldi, L. Baldrati, M. Di Loreto, M. Asa, R. Bertacco, and M. Cantoni, “Blocking Temperature Engineering in Exchange-Biased CoFeB/IrMn Bilayer”, IEEE Transactions On Magnetics 54, 1 (2018)
  4. M. Asa, G. Vinai, J. L. Hart, C. Autieri, C. Rinaldi, P. Torelli, G. Panaccione, M. L. Taheri, S. Picozzi, and M. Cantoni, “Interdiffusion-driven synthesis of tetragonal Chromium (III) oxide on BaTiO3”, Phys. Rev. Materials 2, 033401 (2018)
  5. M. Veis, J. Minar, G. Steciuk, L. Palatinus, C. Rinaldi, M. Cantoni, D. Kriegner, K.K. Tikuisis, J. Hamrle, M. Zahradnik, R. Antos, J. Zelezny, L. Smejkal, P. Wadley, R.P. Campion, C. Frontera, K. Uhlirova, T. Duchon, P. Kuzel, V. Novak, T. Jungwirth, and K. Vyborny, “Band structure of CuMnAs probed by optical and photoemission spectroscopy”, Phys. Rev. B 97, 125109 (2018)
  6. M. Asa, C. Autieri, C. Barone, C. Mauro, S. Picozzi, S. Pagano, and M. Cantoni, “Detecting antiferromagnetism in tetragonal Cr2O3 by electrical measurements”, Phys. Rev. B 100, 174423 (2019)
  7. C. Rinaldi, M. Asa, D. Chrastina, J. L. Hart, M. L. Taheri, I. Pallecchi, D. Marré, and M. Cantoni, “Study and optimization of epitaxial films of Cr and Pt/Cr bilayers on MgO”, Journal of Physics D: Applied Physics 53, 105303 (2019)
  8. M. Asa, C. Rinaldi, R. Pazzocco, D. Petti, E. Albisetti, R. Bertacco, and M. Cantoni, “Electrical readout of the antiferromagnetic state of IrMn through anomalous Hall effect”, J. Appl. Phys. 128(5), 053904 (2020)
  9. M. Asa, C. Autieri, R. Pazzocco, C. Rinaldi, W. Brzezicki, A. Stroppa, M. Cuoco, G. Varvaro, S. Picozzi, and M. Cantoni, “Anomalous Hall effect in antiferromagnetic/nonmagnetic interfaces”, Phys. Rev. Research 2, 043394 (2020)
  10. M. Asa, C. Rinaldi, L. Nessi, D. Chrastina, D. Petti, E. Albisetti, R. Bertacco, and M. Cantoni, “Epitaxy and controlled oxidation of Chromium ultrathin films on ferroelectric BaTiO3 templates”, J. Cryst. Growth 558, 126012 (2021)