Magnetic Information Storage in Antiferromagnet Spintronic Devices

Funding Institution: Fondazione Cariplo, grant 2013
People: Prof. Matteo Cantoni (Project leader)
Partners: CNR-SPIN L’Aquila (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.
      Cr-based planar devices
    • 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.
      Pt/Cr Hall cross
    • 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.Cr2O3/BaTiO3 heterostructure

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.

People involved in the project

Prof. Matteo Cantoni, POLIMI – associated professor, PI
Prof. Riccardo Bertacco, POLIMI – full professor
Dr. Daniela Petti, POLIMI – associate professor
Dr. Christian Rinaldi, POLIMI – assistant professor
Dr. Marco Asa, POLIMI – Ph.d. student
Dr. Lorenzo Baldrati, POLIMI – Ph.d. student (now post-doc researcher)
Dr. Matteo di Loreto, POLIMI – graduate student
Dr. Riccardo Pazzocco, POLIMI – graduate student
Dr. Alessandro Stroppa, CNR-SPIN – III level researcher
Dr. Silvia Picozzi, CNR-SPIN – II level researcher
Dr. Evgeny Plekhanov, CNR-SPIN – post-doc researcher
Dr. Domenico di Sante, CNR-SPIN – post-doc researcher
Dr. Carmine Autieri, CNR-SPIN – post-doc researcher

Selected publications (10)

  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), doi 10.1002/aelm.201600085
  2. E. Albisetti, D. Petti, M. Pancaldi, M. Madami, S. Tacchi, J. Curtis, W. P. King, A. Papp, G. Csaba, W. Porod, P. Vavassori, E. Riedo, and R. Bertacco, “Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography”, Nature Nanotechnology 11, 545-551 (2016), doi: 10.1038/nnano.2016.25
  3. E. Plekhanov, A. Stroppa, and S. Picozzi, “Magneto-electric coupling in antiferromagnet/ferroelectric Mn2Au/BaTiO3 interface”, J. Appl. Phys. 120, 074106 (2016), doi: 10.1063/1.4961213
  4. R. Bertacco and M. Cantoni, “New Trends in Magnetic Memories”, book chapter in G. Varvaro and F. Casoli (eds), “Ultra-High-Density Magnetic Recording: Storage Materials and Media Designs”, Pan Stanford, 2016, ISBN: 978-981-4669-58-0/978-981-4669-59-7
  5. 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 PP, 1 (2018), doi: 10.1109/TMAG.2017.2787623
  6. 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), doi: 10.1103/PhysRevMaterials.2.033401
  7. 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), doi: 10.1103/PhysRevB.97.125109
  8. M. Asa, C. Autieri, R. Pazzocco, C. Rinaldi,  W. Brzezicki, A. Stroppa, M. Cuoco, S. Picozzi and M. Cantoni, “Anomalous Hall effect in antiferromagnetic/non-magnetic interfaces”, ArXiv: 1904.0354, submitted to PRL (2019)
  9. C. Rinaldi, M. Asa, D. Chrastina, J. L. Hart, M. L. Taheri, and M. Cantoni, “Structural and chemical characterization of epitaxial Chromium films and Pt/Cr bilayers on MgO”, submitted to J.Phys.D (2019)
  10. M. Asa, C. Autieri, C. Barone, C. Mauro, S. Picozzi, S. Pagano, and M. Cantoni, “Disclosing antiferromagnetism in tetragonal Cr2O3 by electrical measurements”, submitted to PRB (2019)