Magnetooptical, optical, and magnetotransport properties of Co/Cu superlattices with ultrathin cobalt layers

• Published in: Physics of the solid state Vol. 59; no. 1; pp. 53 - 62
• Main Authors: Lobov, I.D, Kirillova, M.M, Makhnev, A.A, Romashev, L.N, Korolev, A.V, Milyaev, M.A, Proglyado, V.V, Bannikova, N.S, Ustinov, V.V
• Format: Journal Article
• Language: English
• Published: Springer 01.01.2017
• Subjects: Cobalt; Electric properties; Ferromagnetism; Magnetization
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S1033410100

We investigated the field dependences of the magnetization and magnetoresistance of superlattices [[Co([t.sub.x], [Angstrom])/Cu(9.6 [Angstrom])].sub.30] prepared by magnetron sputtering, differing in the thickness of cobalt layers (0.3 [Angstrom] < [t.sub.Co] [less than or equal to] 15 [Angstrom]). The optical and magnetooptical properties of these objects were studied by ellipsometry in the spectral region of [??][omega] = 0.09-6.2 eV and with the help of the transverse Kerr effect ([??][omega] = 0.5-6.2 eV). In the curves of an off-diagonal component of the tensor of the optical conductivity a of superlattices with [t.sub.Co] = 3-15 [Angstrom], a structure of oscillatory type ("loop") was detected in the ultraviolet region, resulting from the exchange splitting of the 3d band in the energy spectrum of the face-centered cubic structure of cobalt (fcc Co). Based on magnetic experiments and measurements of the transverse Kerr effect, we found the presence of a superparamagnetic phase in Co/Cu superlattices with a thickness of the cobalt layers of 3 and 2 [Angstrom]. The transition from superlattices with solid ferromagnetic layers to superparamagnetic cluster-layered nanostructures and further to the structures based on Co and Cu ([t.sub.Co] = 0.3-1 [Angstrom]) with a Kondo-like characteristics of the electrical resistivity at low temperatures is analyzed.