HIGH-SPEED SWITCHING IN PARTICULATE MAGNETIC RECORDING MEDIA

The development of a fast pulsed field magnetometer which can produce pulsed magnetic fields of amplitude up to 450 Oe is described in detai l. The pulse width can be adjusted from 0.8 ns upwards, with rise time s of as little as 105 ps. The system has been used to examine switchin g speed limitations in materials commonly used in particulate recordin g media. Measurements of the remanence coercivity as a function of tim e down to 10(-9) s show that the analysis of magnetization reversal in terms of the high-energy-barrier approximation for the relaxation tim e is still valid. However, ii appears that the limiting factor for thi s analysis is when the product of the effective measurement time and t he attempt frequency (t(eff)f(O)) approaches unity.