Irreversible processes in Bloch wall motion

Abstract

We report experimental results on the motion of a 180° Bloch wall in a Fe-Si single-crystal frame. Below a critical velocity ẋ1, the irreversible wall motion takes place by a large number of small, independant, thermally activated jumps. The onset of large jumps at the critical velocity has the character of an instability. At intermediate velocities, the wall moves by large, reproducible jumps. At a second threshold velocity ẋ2, those jumps begin to break up into smaller and smaller jumps. The evolution of the Barkhausen noise and its power spectrum suggests an analogy with the onset of a turbulent flow. Those phenomena are discussed in terms of thermally activated magnetization processes.

Experimental Consideration of Conditions for Measuring Residual Stresses of Rails Using Magnetic Barkhausen Noise Method

“…The number of these cycles is determined by a user-selectable measurement time constant. In practice, the system measures the induced voltage generated by Bloch wall jump [ 36 , 37 ], but the last registered amplitude value is the result of the absolute current incorporated into the internal circuit. Therefore, the magnetic Barkhausen noise intensity values are displayed in relative unit (r.u.).…”