Origin of perpendicular magnetic anisotropy in Co/Ni multilayers

• Published in: Physical review. B 2017-07, Vol.96 (2), Article 024401
• Main Authors: Arora, M., Hübner, R., Suess, D., Heinrich, B., Girt, E.
• Format: Article
• Language: English
• Subjects: Anisotropy; Bilayers; Cobalt; Ferromagnetic resonance; Ferromagnetism; Gold; Magnetic anisotropy; Multilayers; Reduction; Roughness; Superconducting quantum interference devices; Transmission electron microscopy; X-ray diffraction
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.96.024401

We studied the variation in perpendicular magnetic anisotropy of (111) textured Au/N×[Co/Ni]/Au films as a function of the number of bilayer repeats N. The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N≤10 and then moderately decreases for N>10. The model we propose reveals that the decrease of the anisotropy for N10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N.