Giant magnetoimpedance effect in Co70Fe5Si15B10 and Co70Fe5Si15Nb2.2Cu0.8 B7 ribbons
Giant magnetoimpedance (GMI) effect has been observed in Co70Fe5Si15B10 and Co70Fe5Si15Nb2.2Cu0.8 B7 melt-spun amorphous ribbons. The magnetoimpedance (MI) of these samples has been studied up to a frequency of 10 MHz and varying a dc magnetic field (Hdc) within 150 Oe. A maximum change of 89% in MI has been observed for Co70Fe5Si15Nb2.2Cu0.8 B7 composition around a frequency of 3.1 MHz. Substitution of Cu and Nb for B in an initial Co70Fe5Si15B10 composition forming the Co70Fe5Si15Nb2.2Cu0.8 B7 composition not only favors the GMI effect but also gives rise to the sensitivity of the magnetic response (∼18%/Oe), which is very beneficial for magnetic sensors applications. The GMI effect for both samples annealed at 550 K is further enhanced due to the presence of the ultrasoft magnetic materials, compared to their as-quenched samples.