A dynamic determination of the anisotropy field and the damping constant of thick magnetic films

A new dynamic method for the measurement of Hkand the damping constantTof thick magnetic films is presented from both the theoretical and practical standpoint. The method is based on a property of the differential equation (1), which has been found to be adequate if applied to the read cycle. It is found that, if the easy-axis sense signals obtained with linearly rising hard-axis fields of different rise times are plotted vs. the respective hard-axis fields, the maxima of the sense signals lie almost precisely on a straight line. This straight line cuts the field axis at Hk. From the slope of this line it is possible to deduceT, which is primarily the eddy-current time constant for thick films. The resistivity of the magnetic material can, in this case, be evaluated directly if the physical dimensions of the film are known. The influence of dispersion and skew is discussed and found to be reasonably small. The further advantages are that no instrumental integration is needed and that the reading is quite precise. Small variations of Hkcan, therefore, be easily recorded. Practical results obtained with thick magnetic films illustrate this method.