Magnetic ordering in epitaxial ultrathin Pt/W/Co/Pt layers

•Epitaxial layered stacks Pt/W(dW)/Co(dCo)/Pt were grown by MBE.•Magnetic anisotropy strongly depends on W layer thickness dW.•The presence of Dzyaloshinskii Morya interaction was proved by BLS.•Bubble-like domain structure with micrometer range diameter was observed. We discuss the magnetic properties of epitaxial Pt/W(dW)/Co(dCo)/Pt layered films as a function of W(dW) and Co(dCo) layer thicknesses. The samples were investigated by means of: (i) polar magnetooptical Kerr effect based magnetometry and microscopy as well as (ii) Brillouin light scattering (BLS) spectrometry. The bottom W layer exhibits a strong influence on the magnetic anisotropy, dCo-dependent spin reorientation transition and magnetic polarization of atoms forming the interfaces. The areas with (i) in-plane, (ii) out-of-plane, (iii) superparamagnetic with out-of-plane anisotropy, and (iv) nonmagnetic states appear with dCo decrease. The dW driven transition from hard to soft magnetic material with out-of-plane magnetization was found. The observed domain structures (micrometer range bubbles, stripes and dendritic-like) at out-of-plane state are very sensitive to dCo, dW thicknesses and external magnetic field. The presence of Dzyaloshinskii-Moriya interaction was deduced from BLS measurements.