SOLID-STATE AND PLASMA RADIO PHYSICS Origins of Giant Magnetic Impedance Effect in Magnetic Nanostructures in Millimeter Waveband

ABSTRACT : The dependence of a complex transmission coefficient of the electromagnetic wave passing through multilayered and granular nanostructures demonstrating giant magnetic impedance phenomenon as a function of an external magnetic field has been explored in the millimeter waveband ( f =34 GHz). The magnetic multilayer film Fe 6 (Co 1 /Cu 2 ) 16 and magnetic granular film Co 51.5 Al 19.5 O 29 have been investigated. The maximum magnitudes of the relative module of the complex transmission coefficient 2% and its phase shift 1 o ΔϕT ≈ have been detected. The interrelation between complex impedance Z • and the effective conductivity of magnetic nanostructure is analyzed. Magnetic nanostructures demonstrating Giant Magnetic Impedance (GMI) and Tunnel Magnetic Impedance (TMI) are of great interest today from the point of view of their applicability in modern technologies. Particularly the opportunity to use such objects in megahertz band as magnetic fields sensors [1], spintronic devices (diodes, transistors) [2] is under intensive study. However, the strong demand of modern technology is a permanent increasing the operating frequencies of the corresponding devices. Thus, the examination of applicability of the magnetic nanostructures for higher frequencies, namely, up to Extra-High Frequencies (EHF)-band (millimeter waveband) is a very important contemporary problem [3-5]. One of the principal questions is – whether the GMI phenomenon is defined only by active losses in nanostructure or some reactive processes take place as well. 1285