High Frequency Magnetic Properties and Magnetic Domain Patterns of Ultrathin Co-Based Amorphous Alloy Ribbon Cores

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Ultrathin zero magnetostrictive ((Fe-Co) Cr_y)_X(Si-B)_<100-x'>(x=75-81), (Y=0.05, 0.06) amorphous ribbons were fabricated in vacuum and the following results were obtained.(1) The ribbons obtained were 3-10 mum thick and about 5 mm wide, and had good surface smoothness and dimensional uniformity.(2) Extremely low core loss beyond 100 kHz was attained by thickness reduction. The loss of 5.5 mum thick ribbons at 100 kHz and 1 MHz were 16 (mW/cc) and 1.0 (W/cc) for maximum flux density B_m=0.1 T. Moreover, in the case of 6.0 mum thick ribbon with transverse magnetic field annealing, the loss at 100 kHz and I MHz were 10 (mW/cc) and 700 (mW/cc). These values were about 1/8-1/3 of those of Mn-Zn high-frequency ferrites or 5 mum Supermalloy tape wound cores.(3) Markedly high initial permeability was also obtained. The values of 6.0 mum thick ribbons with transverse field annealing at 1 MHz and 10 MHz were about 13000 and 2200 for a driving field H_m=2 mOe, respectively.(4) The domain patterns of some ultrathin ribbons were observed by the Kerr effect. The effect of transverse magnetic field annealing on the magnetic properties was also studied and their relation to the soft magnetic properties was discussed.