Issues in Determining Activation Volume in Magnetic Recording Media

抄録

The field dependence of the activation volume(V_A)is determined for longitudinal recording media by several different methods. For two methods, which use the irreversible magnetisation, V_A is found to increase for larger reversing fields up to the coercivity(H_C). The V_A as determined from the time dependence of the total magnetisation including the reversible magnetisation, yields the opposite behavior : V_A is found to be much larger at low fields and found to decrease for larger reversing fields up to H_C. The difference between the methods is found to be attributed to the large difference between the total magnetisation and irreversible magnetisation, which is particularly large for small reversing fields. Around H_C however, the different methods yield comparable results.