ISSN 0005-1179, Automation and Remote Control, 2008, Vol. 69, No. 10, pp. 1801–1807. c  Pleiades Publishing, Ltd., 2008. Original Russian Text c  S.I. Kasatkin, D.V. Vagin, P.A. Polyakov, O.P. Polyakov, 2008, published in Avtomatika i Telemekhanika, 2008, No. 10, pp. 168–175. TECHNICAL TOOLS IN CONTROL Frequency Characteristics of the One-layer Anisotropic Magnetoresistive Sensitive Nanoelements 1 S. I. Kasatkin, ∗ D. V. Vagin, ∗ P. A. Polyakov, ∗∗ and O. P. Polyakov ∗∗ * Trapeznikov Institute of Control Sciences, Russian Academy of Sciences, Moscow, Russia ** Moscow State University, Moscow, Russia Received April 8, 2008 Abstract— The high-frequency characteristics of the one-layer anisotropic magnetoresistive strip—the magnetosensitive nanoelement of the magnetic field sensor—were analyzed on the basis of the Landau–Livshits–Hilbert equation. The results of this study were shown to coincide completely with the linear microwave theory. The strip frequency characteristics were analyzed for low-anisotropy and high-anisotropy FeNiCo ferromagnetic films of various thickness, strip width, easy magnetization direction, and fixed external magnetic field. PACS number: 07.07.Df DOI: 10.1134/S0005117908100135 1. INTRODUCTION The anisotropic magnetoresistive (AMR) sensors of magnetic field and current based on the metallic one-layer ferromagnetic nanostructures remain one of the basic types of devices that are internationally designed and manufactured despite a small (up to 2.5%) value of the AMR effect and the advent of the spin-gate and spin-tunnel MR sensors with high MR effect [1–3]. This fact is due to their high performance, relatively simple integral planar manufacturing technology and, as the result, low cost. The AMR nanoelements have wide temperature range, are radiation resistant, and operable at the passage to the submicron dimensions. Of special interest are their frequency characteristics—the MR nanoelements are used as the playback heads for magnetic disks and tapes, magnetosensitive nanoelements in galvanic isolation, and memory elements in the random-access memories. 2. MODEL FOR ANALYSIS OF THE SENSOR FREQUENCY CHARACTERISTICS The AMR sensors of magnetic field and current are bridge circuits with arms consisting of the MR strips connected serially to the low-resistance nonmagnetic jumpers. One or two planar conductors are formed above the isolating layers. The form of the volt-oersted characteristic V (H )= I ΔR(H ), where I is the strip current, H is the magnetic field intensity, and ΔR(H ) is the variation of the strip magnetic resistance, is defined by the structure of the AMR strips, their position in the bridge circuit, and the control conductors. For the AMR effect, ΔR ∼ cos 2 ϕ, where ϕ is the angle between the strip current and the magnetization vector of the ferromagnetic film. At the moment, in the AMR sensors the FeNiCo MR strips are used. The permalloy that was used before enables reduction in the threshold intensity of the measured magnetic field approxi- mately to 0.1 mOe and sensitivity of the order of 1–3 mV/(V×Oe), but has unstable characteristics because of the great impact of remagnetization of the ferromagnetic films by moving domain bound- aries. The upper range of the measured magnetic field intensity reached 1–2 Oe. Use of the FeNiCo 1 This work was supported by the Russian Foundation for Basic Research, project no. 07-07-12064-ofi. 1801