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Soft magnetic behaviour of nanocrystalline Fe-based glass-coated microwires

C. GARCIA1,* , A. ZHUKOV1, M. IPATOV1, V. ZHUKOVA1,2, J. J. DEL VAL1,3, L. DOMÍNGUEZ4, J. M. BLANCO4, V. LARIN5, J. GONZÁLEZ1

Affiliation

  1. Departamento Física de Materiales, Facultad de Química, Pº Manuel de Lardizabal 3, 20018 San Sebastián, Spain
  2. TAMag Ibérica S.L., Parque Tecnológico Miramón, Pº Mikeletegi 56, 1ª Planta, 20009 San Sebastián, Spain
  3. Unidad Física Materiales y Centro Mixto CSIC-UPV/EHU, San Sebastián, Spain
  4. Departamento Física Aplicada I, EUP, Plaza Europa s/n, 20018 San Sebastián, Spain
  5. MFTI, Kishinev, Moldova

Abstract

Microstructural and magnetic behaviours of two thin Fe-rich glass-coated microwires (Fe73.5Cu1Nb3Si13.5B9 and Fe79Hf7B12Si2) with a nanocrystalline structure of such materials are presented. The nanocrystalline state is obtained by heating (300 - 700 ºC, 1 hour) the precursor amorphous microwires. Structural characteristics of the as-cast and annealed samples were determined, at room temperature, by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Such techniques allow to obtain the evolution of the grain size and relative fraction volume (5 - 65%) of the nanograins. Thermal dependencies of Hc are qualitatively similar in both compositions and results to be also qualitatively similar to that reported for the classical Finemet ribbon. In fact, Hc decreases from the as-cast (relaxation process) showing a maximum around 450 ºC (pre-nucleation of nanograins) decreasing significantly between 500-600 ºC (exchange coupling of the nanograins). It is remarkable to note that the Hc values are larger in these glass-coated microwires as comparing with the nanocrystalline Finemet ribbon of similar composition. Such effect should be ascribed to the presence of the glass insulating sheath inducing strong and complex internal stresses on the metallic nucleus which affects dramatically the soft magnetic character..

Keywords

Soft magnetic microwires, Transmission electron microscopy, X-ray diffraction technique, Coercivity.

Submitted at: Sept. 5, 2006
Accepted at: Sept. 13, 2006

Citation

C. GARCIA, A. ZHUKOV, M. IPATOV, V. ZHUKOVA, J. J. DEL VAL, L. DOMÍNGUEZ, J. M. BLANCO, V. LARIN, J. GONZÁLEZ, Soft magnetic behaviour of nanocrystalline Fe-based glass-coated microwires, Journal of Optoelectronics and Advanced Materials Vol. 8, Iss. 5, pp. 1667-1671 (2006)