Sensitivity of an Active Head Using NiFe/Al2O3 Multilayered Films

The sensitivity of a magnetic readout head employing induced RF permeability changes in NiFe/Al2 O3 multilayered films (an active head) has been investigated by measuring the output voltage response to magnetic fields, taking the film thickness and width as parameters. All thick multilayered films had low coercivity and high permeability at frequencies of less than 50 MHz, though they exhibited a small decrease in induced RF permeability around 600 MHz, even when the film width was reduced to 10 µm. The sensitivity of all thick films rose by more than ten times compared with NiFe single-layered films, due to improvements in the soft magnetic properties and reduced eddy currents.