Domain-Wall Motion in Barium Ferrite Single Crystals

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Abstract
The 180° domain‐wall motion in barium ferrite single crystals has been studied by the pulsed‐magnetic‐field technique described in a previous article. The domain‐wall velocity has been measured as a function of the internal magnetic field in a range from 50 to several hundred Oe and at temperatures of 80° and 293°K. The rate of increase of the applied magnetic field dHa/dt has no apparent effect if it does not exceed 1.6 kOe/μsec. Reasonable agreement is found between the wall velocities as measured and values foreseen on the basis of the model proposed by Hagedorn and Gyorgy to explain wall mobility in YIG. An accurate analysis of the dependence of the wall velocity on the magnetic‐field intensity suggests the existence of a threshold field Ht, which depends on the value of the damping constant α and defines the point of transition from one motion mechanism to another. We think that Ht may be identified with the critical field H0=2παMs which appears in a solution given by Walker to the domain‐wall equations, and that the model proposed by Hagedorn and Gyorgy simply applies to the case H>Ht. This means that, rather than the damping constant α alone, the quantity k=H/2παMs is to be taken as a suitable parameter to distinguish between different motion mechanisms.