Tunable Magnetic Skyrmions in Ferrimagnetic Mn${}_4$N

Abstract

Thin films of ferrimagnetic Mn${}_4$N are candidate materials to host magnetic skyrmions that have demonstrated thermal stability up to 450${}^{\circ }$C. However, there are no experimental reports observing skyrmions in this system. Here, we discuss the results of sputter grown 15-17~nm Mn${}_4$N thin films on MgO substrate capped with Pt${}_{1-x}$Cu${}_x$ layers. Vibrating sample magnetometry measurement of out-of-plane hysteresis loops confirmed that magnetic properties are insensitive to the cap layer composition. Imaging based on magnetic force microscopy measurements observed 300 to 50~nm sized skyrmions, as the Cu concentration was increased from $x$ = 0 to 0.9. We performed density functional theory calculations and found that the interfacial Dzyaloshinskii-Moriya interactions (iDMI) follow a trend: Mn${}_4$N/MgO(001) $<$ Cu/Mn${}_4$N(001) $<$ Pt/Mn${}_4$N(001). We infer from these calculations that $x$ in Pt${}_{1-x}$Cu${}_x$ capping layer can serve as a robust tuning knob to tailor the iDMI and control the skyrmion size. This work provides guidance to achieve smaller Néel-type skyrmions in Mn${}_4$N thin films, which is an important step forward for building thermally stable skyrmionic devices.

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Cited by in corpus (1)

• Interfacial Mixing Effect in a Promising Skyrmionic Material: Ferrimagnetic Mn${}_4$N