EXCHANGE-COUPLED NI-FE FE-MN, NI-FE/NI-MN AND NIO/NI-FE FILMS FOR STABILIZATION OF MAGNETORESISTIVE SENSORS/

We have studied the unidirectional anisotropy field (H-UA) and coerciv ity (H-CE) in exchange-coupled Ni-Fe/Fe-Mn, Ni-Fe/Ni-Mn and NiO/Ni-Fe films as functions of thickness and temperature, and evaluated these f ilms for the stabilization of magnetoresistive (MR) sensors. The as-de posited Ni-Fe/Fe-Mn and NiO/Ni-Fe films exhibit strong exchange coupli ng, while the Ni-Fe/Ni-Mn films require annealing to enhance exchange coupling, Both H-UA and H-CE follow an inverse dependence of the Ni-Fe film thickness in all cases, as expected from the interface nature of exchange coupling. The Fe-Mn film thickness required for the onset of exchange coupling is much smaller than the Ni-Mn and NiO film thickne sses, The thermal stability of the Ni-Fe/Ni-Mn films is superior to th at of the Ni-Fe/Fe-Mn and NiO/Ni-Fe films. To explain annealing effect s on exchange coupling in the Ni-Fe/Ni-Mn films, we propose an exchang e-coupling model consistent with models applied to the Ni-Fe/Fe-Mn and NiO/Ni-Fe films in previous studies. Uniform-field tests of the MR se nsors longitudinally biased by the three types of exchange-coupled fil ms show quiet and stable MR responses in all cases, We evaluate the ex change-coupled films based on desired properties for the sensor stabil ization, and then discuss their merits and deficiencies.