Emergence of Room Temperature Magnetotransport Anomaly in Epitaxial Pt/γ′-Fe4N/MgO Heterostructures toward Noncollinear Spintronics

摘要

Noncollinear spin textures have attracted much attention due to their novel physical behaviors in heavy/ferromagnetic metal (HM/FM) systems. The transport anomaly, appearing as contrast humps in Hall resistivity curves, is the mark of noncollinear spin textures. Here, the epitaxial Pt/γ′-Fe_(4)N bilayers with noncollinear spin textures were obtained by facing target sputtering. Large micromagnetic Dzyaloshinskii–Moriya interaction coefficient D of 2.90 mJ/m~(2) appears in Pt/γ′-Fe_(4)N/MgO systems, which is larger than 2.05 mJ/m~(2) of Pt/Co/MgO systems with skyrmionic states. Moreover, at 300 K, magnetic bubble-like domains appear in Pt/γ′-Fe_(4)N bilayers that just possess a 3 nm thick ferromagnetic layer instead of [HM/FM]_(n) or [HM_(1)/FM/HM_(2)]_(n) multilayers. Additionally, a room-temperature transport anomaly appears in Pt/γ′-Fe_(4)N/MgO systems. The contrast humps of Pt(3 nm)/γ′-Fe_(4)N(t _(Fe_(4)N) ≤ 4 nm)/MgO heterostructures are not sharp due to the nonuniform distributions of the magnetic bubble-like domains with various sizes and irregular shapes, as observed by the magnetic force microscopy. The discovery of epitaxial Pt/γ′-Fe_(4)N bilayers with noncollinear spin states is more crucial than that of polycrystalline or amorphous HM/FM systems for reducing ohmic heating, which provides a candidate for noncollinear spintronic applications.