Magnetic resonance in multilayer Gd/Si/Co magnetic films
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R, AND PHASE TRANSITIONS IN CONDENSED SYSTEMS
Magnetic Resonance in Multilayer Gd/Si/Co Magnetic Films G. S. Patrina,c, V. O. Vas’kovskiœb, A. V. Svalovb, E. V. Eremina, M. A. Panovaa, and V. N. Vasil’eva aKirenskiœ
Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia bUral State University, pr. Lenina 51, Yekaterinburg, 620083 Russia cKrasnoyarsk State University, pr. Svobodnyœ 79, Krasnoyarsk, 660041 Russia e-mail: [email protected] Received July 22, 2005
Abstract—The magnetic properties of multilayer Gd/Si/Co magnetic films are experimentally studied by electron magnetic resonance and analyzed theoretically. The introduction of a semiconductor silicon interlayer is found to substantially affect the magnetic interlayer coupling and the magnetic dynamics of the system. The interlayer coupling is shown to be ferromagnetic for the (Gd/Si)n films and to be antiferromagnetic for the (Gd/Si/Co/Si)n films. The temperature dependences of the exchange parameters and the gyromagnetic ratios are determined. Possible mechanisms responsible for the formation of the interlayer coupling are discussed. PACS numbers: 75.70.Cn, 76.50.+g DOI: 10.1134/S1063776106010158
1. INTRODUCTION
2. EXPERIMENTAL
(Gd/Si/Co/Si)n films have been found to be very interesting objects for studying the modifications of interlayer exchange couplings in multilayer film structures under external actions. As was experimentally detected in [1], the temperature dependence of the magnetization of such films has a compensation point Tcomp , whose value depends on the thickness of the silicon interlayer tSi , just as in the case of bulk alloys rare-earth element–3d transition metal. In magnetic fields H ≤ 500 Oe, a field-dependent specific feature is observed in the vicinity of this point at T < Tcomp [2]. The behavior of this specific feature can be explained on the assumption that, along with bilinear coupling, the interlayer coupling between magnetic layers contains a biquadratic contribution and that both contributions depend on the semiconductor-layer thickness, the temperature, and the magnetic field. In low magnetic fields, the magnetization of the films can behave similarly to spin-glass behavior [3], which also supports the presence of a biquadratic contribution in these films.
The films to be studied were fabricated by ion-beam rf sputtering on a glass substrate [4]. The samples consisted of stacks and were protected from above and below by silicon of a thickness tSi = 200 Å. The layer thicknesses in all films were the following: tGd = 7.5 nm, tCo = 3 nm, and variable tSi . All thickness parameters were set by the time of sputtering of the corresponding layers at the given deposition rates of different materials. With small-angle X-ray scattering, we detected a layered character of the films and confirmed the nominal values of the structure period (with an error of ±2 Å). Moreover, as was shown by X-ray diffraction and electron-microscopic examination, the structure of the films is clo
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