REMANENCE COERCIVITY OF RECORDING MEDIA IN THE HIGH-SPEED REGIME

New measurements of the switching characteristics in short pulse field s of CrO2 particulate tape and CoNi metal evaporated tape are reported which complete a survey of materials used in flexible media. An unamb iguous measure of the is the remanence coercivity H-CR results which i ncreases as the pulse width tau decreases. Three mechanisms which coul d contribute to the increase are thermally assisted switching, damping limited switching and changes in the reversal process. In samples wit h high viscosity, the results are in excellent agreement over 12 decad es with the simple thermal model proposed by Sharrock within the appli cable range of tau > 1/f(0), where f(0) is the attempt frequency equal to 10(9) Hz. For tau < 1/f(0), H-CR continues to increase; for exampl e, in CrO2 at tau = 0.6 ns, it reaches 1.8 times the value for tau sim ilar to 1.0 s. In samples with low viscosity, the rapid increase in H- CR for 2 > 1/f(0) in some materials confirms that other mechanisms are dominant in these materials.