Optimizing the planar structure of (1 1 1) Au/Co/Au trilayers

Abstract

Au/Co/Au trilayers are interesting for a range of applications which exploit their unusual optical and electronic transport behaviour in a magnetic field. Here we present a comprehensive structural and morphological study of a series of trilayers with 0-7 nm Co layer thickness fabricated on glass by ultrahigh vacuum vapour deposition. We use a combination of in situ electron diffraction, atomic force microscopy and x-ray scattering to determine the optimum deposition conditions for highly textured, flat and continuous layered structures. The 16 nm Au-on-glass buffer layer, deposited at ambient temperature, is found to develop a smooth (1 1 1) texture on annealing at 350 • C for 10 min. Subsequent growth of the Co layer at 150 • C produces a (1 1 1) textured film with lateral grain size of ∼150 nm in the 7 nm-thick Co layer. A simultaneous in-plane and out-of-plane Co lattice expansion is observed for the thinnest Co layers, converging to bulk values for the thickest films. The roughness of the Co layer is similar to that of the Au buffer layer, indicative of conformal growth. The 6 nm Au capping layer smoothens the trilayer surface, resulting in a surface roughness independent of the Co layer thickness.

Surface-magnetoplasmon nonreciprocity effects in noble-metal/ferromagnetic heterostructures

“…Complete details of the deposition conditions, and optimization of the structure and morphology of the samples can be found elsewhere. 14 To excite the SPP in these structures we have used a Kretschmann configuration, 15,16 where the sample is optically interfaced to a half-cylinder glass prism by a matching index fluid, placing the glass substrate in contact with the prism and leaving the Au capping layer in contact with air. The prism is mounted in a goniometer permitting variation of the light incidence angle from a fixed TM polarized HeNe laser ͑632 nm͒.…”

Magneto-optic ellipsometry characterization of Co and SmCo thin films

“…The experimental data are in good agreement with the simulated curves for both the Au/Co/Au and SmCo samples. In the visible wavelength range, ΔM 13 and ΔM 31 values for the Au/Co/Au sample are half the values obtained elsewhere [11] for the 8nm thick Co film on a sapphire substrate. In the infrared, the corresponding ratios are even less.…”

“…Indeed, we obtained a 50% increase in ΔM 13 and ΔM 31 values when we simulated the MO response of the Au/SmCo/Au multilayer on an SF10 substrate using measured permittivity tensor elements for SmCo. …”

“…For complex permittivity tensor elements, we use the notation , where k,l=x,y,z, and assume that holds for diagonal elements. We fitted together the experimental M 13 , M 24 , and M 31 data for opposite magnetic field directions, as these elements reveal the largest MO response for the longitudinal Kerr effect [11]. The differences between normalized MM elements for opposite magnetizations , where and indicate two opposite field directions, are depicted in Fig.…”

“…The Au/Co/Au samples have been grown in a molecular beam epitaxy system on an SF10 glass substrate covered with a 2nm Cr layer at the pressure 10 −8 Pa (see details elsewhere [13]). The nominal thicknesses of Au-bottom, Co, Au-top layers are 25nm, 6nm, and 15nm, respectively.…”