Magnetoimpedance properties of CoNbZr, multilayer CoNbZr/Au and multilayer NiFe/Au thin films

Thin-film giant magnetoimpedance (GMI) structures are promising candidates for high-frequency magnetic sensing, with their performance governed by the interplay of electronic transport, magnetic softness, and ferromagnetic resonance (FMR). Optimisation therefore requires a comprehensive understanding of the properties of soft magnetic materials. This study investigates the structural, electric, magnetic, and GMI properties of sputtered amorphous CoNbZr single layers, amorphous CoNbZr/Au multilayers, and crystalline NiFe/Au multilayers. GMI measurements reveal distinct FMR frequencies of 1.4 GHz (CoNbZr), 0.7 GHz (CoNbZr/Au), and 0.5 GHz (NiFe/Au). Introducing Au interlayers into CoNbZr lowers the FMR frequency by 50% and enhances the maximum GMI ratio by a comparable margin relative to the single-layer film. At 1.8 GHz, the highest GMI performance is observed in a 20 μ m × 5000 μ m CoNbZr/Au strip, yielding 300% with a sensitivity of 249%/kAm − 1 . Under identical conditions, single-layer CoNbZr reaches 180% (169%/kAm − 1 ) and NiFe/Au 280% (183%/kAm − 1 ), confirming the superior response of the CoNbZr/Au multilayer. These improvements are attributed to differences in in-plane demagnetising factors and saturation magnetisations, providing design guidelines for the development of resonant GHz-range GMI sensors. • Amorphous CoNbZr and CoNbZr/Au multilayers investigated for GHz-range GMI sensors. • CoNbZr/Au shows 50% higher GMI ratio and reduced FMR frequency vs. single-layer CoNbZr. • Maximum GMI ratio: 300% at 1.8 GHz with 249%/kA m − 1 sensitivity in 20 μ m × 5000 μ m CoNbZr/Au strip. • Structural, electric, and magnetic analyses link performance to demagnetising factors and M s . • CoNbZr/Au multilayers provide design guidelines for resonant, high-performance GMI sensors.