The anisotropy dependence of ferromagnetic domain-wall widths in crystalline and amorphous metals

We have used the techniques of Lorentz electron microscopy to study the behavior of ferromagnetic domain-wall widths as a function of the magnetic anisotropy constant K and the foil thickness D. This was done by varying the temperature T in crystalline iron and in amorphous Fe75P15C10 for various D’s. Our results are compared with existing theories. We observed an increase in wall width with temperature in crystalline iron and explained this by assuming the width of the wall to be an explicit function of both the anisotropy constant K (T) and the temperature T. After removing the explicit temperature dependence, the experimental results yielded an expression for the wall width of the form 2.5D/K1/6 within the range of ∼1000 Å foil thickness. An increase in wall width with temperature was also observed for walls in amorphous Fe75P15C10. From the measured wall structures we obtained a value of ∼104 erg/cm3 for the effective anisotropy constant of this amorphous alloy.