Single Bloch wall dynamics in amorphous ribbons: A comparison between experimental and theoretical results

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A numerical approach is introduced to study the motion of a single bowed domain wall in an isotropic ferromagnetic lamination under general conditions of time dependence of the exciting magnetic field. A large set of numerical results concerning the behavior of Bloch walls in a magnetostrictive amorphous ribbon (Allied Signal Metglas 2605 SC), submitted to a sinusoidal field of varying amplitude and frequency is reported and discussed. The results are compared with the ones reported in the literature and obtained through different methods of calculation. The present approach allows one to get valuable information on the effect of wall bowing on the magnetic permeability, the so-called magnetic skin effect and the critical field which corresponds to a domain-wall instability resulting in wall multiplication. The peculiar behavior of the phase shift between wall oscillations at the lamination surface and within the lamination bulk appears to be very sensitive to the value of the wall’s surface energy density σw, at least within an appropriate frequency domain, thereby suggesting a reliable method of measuring this quantity. Actual measurements performed on a Metglas 2605 SC ribbon by using a Kerr-effect optical technique are reported and compared with the theoretical predictions. When a tensile stress of about 500 MPa is applied to this highly magnetostrictive material to provide a regular pattern of straight domain walls aligned along the ribbon axis, a value of σw=1.7×10−3 J/m2 is found. This value is consistent with the one calculated from the magnetostriction and the exchange energy coefficient of Metglas 2605 SC, which is between 1.4×10−3 and 1.8×10−3 J/m2. Measurements of the behavior of the wall oscillation amplitude as a function of the field intensity are also reported and discussed.