Domain wall mass in permalloy films

A new type of nonlinear dependence of wall displacement on applied pulse width is studied by the interrupted pulse method in Permalloy films. The phenomenon is attributable to the acceleration and deacceleration of the wall under the applied pulse field and coercive force. The wall relaxation time and wall mass are determined as a function of film thickness. The relaxation time in films thicker than about 700 Å is about 50 ns, which is about thirty times larger than that expected for bulk Permalloy, and decreases rapidly with decreasing film thickness. The measured wall mass is also two to three orders larger than that expected for bulk material. It is found that qualitative agreement is fair between the measured mass and the Schlömann´s recent calculation.