High-frequency magnetoimpedance in multilayer thin films with longitudinal and transverse anisotropy

Giant magnetoimpedance (GMI) effect in NiFe (150 nm)/Cu (500 nm)/NiFe (150 nm) multilayers with longitudinal and transverse induced magnetic anisotropy was studied at frequencies of 300 kHz-3 GHz. Several sensitive elements were built in a single "chip'' configuration. At low and intermediate frequencies the GMI displays a single peak at zero-field for samples with longitudinal and two peaks for the samples with transverse anisotropy. Above 500MHz the observed behaviour in both cases can be explained by the apparition of the ferromagnetic resonance (FMR). Regarding the performance of the sample, the maximum GMI sensitivity values achieved in case of longitunal anisotropy are 6%/Oe from the single peak to the saturation field at 500MHz (quasistatic regime), and 12%/Oe from the FMR peaks to zero-field at 1.12GHz (dynamic regime). Sensitivity values achieved in case of transverse anisotropy are 31%/Oe from the single peak to the saturation field at 70MHz and 17%/Oe from the FMR peaks to zero-field at 0.8 GHz. Small variations of GMI ratio and field sensitivity for different sensitive elements built in a single "chip'' confirm the possibility to use this design for multi-analyte detector construction. (c) 2008 Elsevier B. V. All rights reserved.