Density Functional Theory Investigation of Ferrimagnetic Mn<sub>4</sub>N as a Skyrmion Host

ORAL

Abstract

Skyrmion  devices  have  potential  to  cause  significant  disruption  inthe high-density storage industry.  To maximize performance, nucleated skyrmions should be small and stable around room temperature.  Thinfilms of ferrimagnetic Mn4N show promise with improved stability be-cause of the high N ́eel temperature, low saturation magnetization, and presence  of  perpendicular  magnetic  anisotropy  in  the  thin  film  geometry.   However,  conditions  that  govern  the  skyrmion  size  in  ultra-thin Mn4N films are not known.  Here, density functional theory calculations are used to investigate the salient magnetic properties that govern theskyrmion size in Mn4N thin films.  We calculate the impact of changing both the interfacial composition as well as orientation on the interfacial Dzyaloshinskii-Moriya interaction (iDMI). We predict that Cu substitution in the Pt capping layer reduces the iDMI, which reveals the promise of capping layer composition engineering for tuning the skyrmion size. Results from DFT are validated by growth of a < 20 nm Mn4N thin film on MgO (001) substrate with CuxPt1−xcapping layer.  Imaging using magnetic force  microscopy showed that in CuxPt1−x can serve as a knob to tune the skyrmion size (50–300 nm) at room temperature.

*The Authors thank the Defense Advanced Reearch Project Agency and the Army Research Office under Grant Number W911NF-20-1-028. The views and conclusions contained in this presentation are those of the authors and should not be interpreted as representing the official policies, either expressed or implied of, of DARPA, the Army Research Office, or the U.S. Government.

–

Publication: 1) Zhou, W., et al. "Rare-earth-free ferrimagnetic Mn4N sub-20 nm thin films as potential high-temperature spintronic material." AIP Advances 11.1 (2021): 015334.
2) Chung T. Ma., et al. Zhou, W., et al. "Tunable Magnetic Skyrmions in Ferrimagnetic Mn4N", in review for publication in Applied Physics Letters.

Presenters

  • Timothy Q Hartnett

    • University of Virginia
    • Material science and engineering, University of Virginia

Authors

  • Timothy Q Hartnett

    • University of Virginia
    • Material science and engineering, University of Virginia

  • Prasanna V Balachandran

    • University of Virginia
    • Material science and engineering, University of Virginia

  • Chung T Ma

    • Department of Physics, University of Virginia
    • University of Virginia
    • Physics department, University of Virginia

  • Wei Zhou

    • Physics department , University of Virginia

  • Joseph Poon

    • Department of Physics, University of Virginia
    • Univ of Virginia
    • Physics department , University of Virginia