Papers by Keyword: Magnetic Multilayers

Abstract: The technique of finite difference equations is used for analytical investigation of magnetization pattern in magnetic multilayers. The magnetic multilayers with equal magnetic layers and ferrimagnetic multilayers are considered. Heisenberg and biquadratic exchange interactions and uniaxial anisotropy are taken into account. The analytical dependencies of total magnetic moment on external magnetic field are obtained taking into account the strong interaction with the substrate. The significant difference in the behavior of magnetic moment is derived for ferrimagnetic multilayers with odd and even layers number.

Abstract: Magnetic properties and magnetoimpedance of [FeNi/Cu]_n/FeNi/Cu (500 nm)/[FeNi/Cu]_m/FeNi MI asymmetric and symmetric structures were studied for multilayeres with different thickness (25, 50 or 170 nm) of permalloy layers. The asymmetric structures in the case of FeNi layers of 50 nm show higher sensitivities comparing with symmetric structures. Asymmetric multilayered structures with 25 nm thick FeNi layers are an interesting subject for further investigation as the interactions between FeNi layers seem to be providing the best MI response.

Abstract: The model of exchange coupling between ferromagnetic metal layers across a non-degenerate semiconductor spacer with point-like defects is considered. Calculation of an asymptotic behavior of the exchange integral is carried out. The exchange integral is found to alternate its sign depending on the position and filling of the deep impurity energy levels into the spacer. The results provide a basis for interpretation of recent experiments in iron/silicon multilayers.

Abstract: The technique of finite difference equations is used for an analytical investigation of field-induced transitions in magnetic multilayers. Heisenberg and biquadratic exchange interactions and uniaxial anisotropy are taken into account. The analytical dependencies of critical field values determining the stability of ferromagnetic and antiferromagnetic phases on the layers number are obtained.

Abstract: Co/Pt multilayers reside among the best candidates for perpendicular magneto-optic recording. In this work, Co/Pt multilayers were prepared by electron-beam evaporation under ultrahigh vacuum conditions on polyimide. X-ray diffraction measurements revealed the high quality of multilayer stacking. Magneto-optic polar Kerr effect experiments were used in order to obtain magnetization hysteresis loops of the films. We have studied the magnetic-domain morphology on the surface of the films via Magnetic Force Microscopy. The field applied during these measurements was 2.3 kOe oriented perpendicular to the film plane; this field seems to stabilize and enhance out-of-plain stripe domains against in plain domains that may be expected from magnetization curves. Finally, we observed that when the applied field approaches the magnetic saturation field, then the domain morphology turns to be dominated by bubble domains.

Abstract: The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors, offering miniature, highly sensitive, and quick response elements. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for non-destructive testing (as eddy current probes) and smart sensory systems (self-sensing composites). In certain soft magnetic materials, such as composites of amorphous thin wires, the impedance change (MI ratio) can be as high as 600 % in the MHz band and 50-100% at GHz frequencies subjected to small magnetic fields or stresses. Furthermore, special thin-film structures have been proposed to improve the MI performance in miniature elements. This paper discusses physical concepts of MI in multilayered structures including MI ratio enhancement and effect of anisotropy, experimental results proving high sensitivity to the external stimuli for excitation frequencies up to few GHz, practical sensor designs and, finally, the use of MI fibers for tagging the composites to build-in sensing functionality .