Bloch wall motion along the hard direction of Permalloy films due to fast-rising hard-axis pulses is studied. Experimentally, it is found that for a given value of ḣ⊥, the time rate of change of the applied field, wall motion occurs only for fields in excess of a certain minimum or threshold value hth. Two distinct regions exist in this characteristic threshold curve. When ḣ⊥ is large h th is constant and when ḣ⊥ is small h th is a linear function of ḣ⊥. Above h th the wall displacement or movement per pulse increases linearly with driving field until this field approaches the value where the effect of Néel lines becomes important. A theoretical model taking account of both Bloch-Néel wall transitions and the gyromagnetic effect of the spins in the walls and in the surrounding domains is proposed to account for the experimental results. The calculation assumes a reasonable wall structure and that Bloch walls are allowed to move freely except for a coercive force, i.e., a possibly more complicated interaction between the Bloch walls and Néel lines is neglected. With appropriate values of the constants and film parameters, the computation gives very good agreement with experimental results. © 1969 The American Institute of Physics.
