Abstract

   Ferromagnetic materials play an important role in modern electrical and electronic engineering, and therefore a lot of research in physics and materials science is devoted to this field. One of the reasons for the big interest in these materials is that they can be used in a wide set of applications. In this field of materials science the soft magnetic materials with non-equilibrium structure (amorphous and nanocrystalline), discovered more than 30 years ago, are now competitive with conventional crystalline soft magnetic materials. It is known that the highest saturation magnetization (above 1.8 T) is reached in FeCo-based amorphous alloys. In this diploma work I report on the replacement of Ni by Co in well-known Fe₄₀Ni₄₀P₁₄B₆ metallic glass and how it affects the magnetic properties and thermal stability. I will also report on a new concept in characterization of melt-spun ribbons, namely employing FFT to characterize ribbons surface morphology.
   The Fe₄₀Co₄₀P₁₄B₆ metallic alloy has been prepared in a glassy state by a melt-spinning process. With this technique we produce rather thin and long ribbons of amorphous material. The 15-25 mm thick as-quenched ribbons have superior soft magnetic properties compared with those of well-known Fe₄₀Ni₄₀P₁₄B₆ glass: the saturation magnetization is about 1.45 T, incremental magnetic permeability m_max ~ 90000, coercive field as low as 183 mOe, and hysteretic losses is 0.56 W/kg @ 70 Hz. The crystallization temperatures, determined by differential scanning calorimetry, were found to be approximately 60 K higher than those for the FeNi-based alloy, indicating the enhanced thermal stability of FeCo-glass.
   Results obtained in the diploma work have been reported on Material Research Society Fall2000 meeting (Boston, Nov. 27 - Dec. 1, 2000) and will be presented at 8th Joint MMM-Intermag Conference (San Antonio, Jan. 7-11, 2001).  
   Processing of melt-spun ribbons will be demonstrated on request to keep ribbons for Christmas tree decoration!