Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

Abstract

Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

Room temperature skyrmion ground state stabilized through interlayer exchange coupling

“…With the Ni base-layer being magnetized in an out-of-plane singledomain state, this coupling acts as a virtual magnetic field along the out-of-plane direction. 36 This picture can be corroborated by changing the thickness of the Cu interlayer to emergence of spin spirals, skyrmions, and single domain states in the experimental observation in helical magnets 5,6,[9][10][11][12][13] or cycloidal magnets, 15,16 and in Monte-Carlo simulation 43 in the presence of external magnetic field.…”

“…33 The Cu/Ni/ Cu(001) structure underneath the Fe/Ni films is designed to modify this ground state: the Ni layers have perpendicular magnetic anisotropy and, 34 similar to application of an external magnetic field, exchange coupling through the Cu spacer layer lifts the degeneracy of "up" and "down" domains in the Fe/Ni film on top. 35,36 By tuning the thickness of the Cu interlayer, we find that the spin texture in the Fe/Ni bilayer can be adjusted between single domain, stripe domain, or skyrmion ground states.…”

“…1(b) illustrates this well-known effect. In this letter, we introduce a similar change of the magnetic domain ground state of the Fe/Ni bilayer by applying a virtual magnetic field H ef f that results from the coupling through a non-magnetic Cu spacer layer to a perpendicularly magnetized Ni film, 36 as laid out in Fig. 1(c).…”

“…This indicates that the virtual magnetic field due to interlayer coupling through the d Cu ¼ 14.6 ML Cu interlayer to the Ni base-layer underneath is negligible compared to the dipolar stray field of the Fe/Ni bilayer. 36,42 The virtual magnetic field changes as a function of the thickness of the Cu interlayer. 35,36 Figs.…”

“…36,42 The virtual magnetic field changes as a function of the thickness of the Cu interlayer. 35,36 Figs. 2(c) and 2(d) show results for d Cu ¼ 8.6 ML, where the stripe domain phase no longer appears.…”