Imaging Spin-Reorientation Transitions in Consecutive Atomic Co Layers on Ru(0001)

Abstract

By means of spin-polarized low-energy electron microscopy, we show that the magnetic easy axis of one to three atomic-layer thick cobalt films on Ru(0001) changes its orientation twice during deposition: One-monolayer and three-monolayer thick films are magnetized in plane, while two-monolayer films are magnetized out of plane. The Curie temperatures of films thicker than one monolayer are well above room temperature. Fully relativistic calculations based on the screened Korringa-Kohn-Rostoker method demonstrate that only for two-monolayer cobalt films does the interplay between strain, surface, and interface effects lead to perpendicular magnetization.

Perpendicular magnetic anisotropy of cobalt films intercalated under graphene

“…which permits us to estimate the contribution of the graphene/Co interface to the PMA: [25] showed that the value of K vacuum/Co is close to zero in the case of Co films strained to match the 0.277 nm lattice constant of Pt(111), lattice strain-resolved ab-initio calculations [26] showed that the value of the surface anisotropy…”

Magnetic imaging with spin-polarized low-energy electron microscopy

“…The direction of the magnetization vector can be mapped with high angularand spatial resolution while the spin transition occurs, for instance when the thickness of the structure is increased, when the temperature is changed, or when the surface topography, morphology or chemistry is modified. Co on Au(111) [54], Co on Ru(0001) [61] and Co/Ru(0001) with noble-metal capping layers [62], Au/Co on Ru(0001) [54] and on W(110) [53,59], Fe on Cu(001) [67], Fe/Ni bilayers on Cu(001) [73] and Fe-Co alloys on Au(111) [82] are examples of systems exhibiting SRTs that have been investigated using SPLEEM. The capabilities of SPLEEM make it a complementary approach to other techniques, but also open new opportunities for magnetic investigations.…”

Unlocking Bloch-type chirality in ultrathin magnets through uniaxial strain

“…We focus on Fe/Ni bilayer grown on W(110) substrates, where the very large spin Hall angle of tungsten 23 is combined with two-fold symmetry at the (110) interface and perpendicular magnetic anisotropy of the magnetic layer [24][25][26] . Using spin-polarized low-energy electron microscopy (SPLEEM) [27][28][29] , we observe anisotropic chiral DW spin structures with mixed components of chiral Bloch-and chiral Néel-character. We find that, as a function of the relative orientation of the DWs with respect to the [001] substrate surface direction, the Fe/Ni/W(110) system features chiral Néel walls, mixed chiral walls containing both Néel and Bloch components or non-chiral Bloch walls.…”