Millimeter-sized magnetic domains in perpendicularly magnetized ferrimagnetic Mn₄N thin films grown on SrTiO₃

Abstract

The use of epitaxial layers for domain wall-based spintronic applications is often hampered by the presence of pinning sites. Here, we show that when depositing Mn4N(10 nm) epitaxial films, the replacement of MgO(001) by SrTiO3(001) substrates allows minimizing the misfit, and to obtain an improved crystalline quality, a sharper switching, a full remanence, a high anisotropy and remarkable millimeter-sized magnetic domains, with straight and smooth domain walls. In a context of rising interest for current-induced domain wall motion in rare-2 earth ferrimagnets, we show that Mn4N/SrTiO3, which is rare-earth free, constitutes a very promising ferrimagnetic system for current-induced domain wall motion.

Large Current Driven Domain Wall Mobility and Gate Tuning of Coercivity in Ferrimagnetic Mn4N Thin Films

“…In these systems the DW velocity was clearly observed to vary with the total magnetisation. In the former experiment, a maximum velocity of v=750 m/s for J=3x10 12 A/m 2 was obtained at room temperature using a Ru spacer layer, so that the stack magnetisation was reduced to 8% of the spontaneous magnetisation of a single Co/Ni layer. In the latter one, a peak velocity of 1250 m/s was reported at 240 K (the angular moment compensation temperature) for a current density of 2x10 12 A/m 2 .…”

“…Figure 1.f). The observed scarce nucleation centers with remarkably large domains, at the millimeter scale, with smooth and very long DWs 12 , result from the high crystalline quality. Mn4N films are metallic, with layer resistivity around 180 µ cm at room temperature, comparable to CoFeB-based materials.…”

“…SOT has been found to be an efficient mechanism to drive DWs in non-centrosymmetric multilayers, in which a FM is deposited on a heavy metal like Pt 17,18 . The prototypical example is Pt/Co(0.6nm)/AlOx 25 where the chiral Néel structure acquired by the DWs in the presence of interfacial Dzyaloshinskii-Moriya interaction 16 leads to a high mobility (v=400m/s for J=310 12 A/m 2 ) with a satisfying reproducibility of the DW movements. Higher SOT-driven DW mobilities were obtained recently in a multilayer structure in which two Co/Ni layers were coupled anti-ferromagnetically through a Ru layer 26 , or in GdCo ferrimagnet layers deposited on top of Pt 27 .…”

Molecular beam epitaxy growth of Mn4−Ni N thin films on MgO(0 0 1) substrates and their magnetic properties

“…The existence of a small MS and high PMA has been reported in Mn4N thin films grown on glass [5], Si(001) [6], 6H-SiC(0001) [7], MgO(001) [8][9][10][11][12][13], and SrTiO3(001) [9,14] substrates. These striking features led to a DW velocity of approximately 10 3 m/s with a current density of 1.5 × 10 12 A/m 2 in Mn4N nanowires [15]. Figure 1 shows the antiperovskite structure of Mn4N, where Mn atoms occupy the corner (I) and face-centered (II) sites and an N atom occupies the body-centered site.…”

“…In recent years, antiperovskite nitrides such as Mn4N and their mixed-crystal thin films have attracted attention. The growth of CoxMn4−xN and Fe4−xMnxN thin films by molecular beam epitaxy (MBE) and the evaluation of these crystalline structures and magnetic properties have been reported [14,15]. In this work, we focused on Mn4−xNixN, in which the Mn atoms in Mn4N were partially substituted with Ni atoms.…”