Antiferromagnetic exchange coupled and soft adjacent layer biasings for an MR head by triode sputter deposited films

This paper will investigate the effect of grain size on NiFe/FeMn exchange coupled films. This will be done through deposition methods (diode vs triode deposited films) and thermal treatment of films. Longitudinal biasing at the ends of a magnetoresistive (MR) element is required for Barkhausen noise free response. One approach is to pattern the ends of the ferromagnetic NiFe MR element with FeMn antiferromagnetic film. NiFe/FeMn antiferromagnetic exchange coupled films have been studied by Howard et el using a diode sputtering system. Here we investigate such properties on triode deposited films. Plasma is confined only in the target area away from the substrate in the triode system. Therefore, this is a cooler sputtering process as compared to the diode sputtering system. In the diode sputtering system electron bombardment beats up the surface of the substrate. This will affect siren and grain size in the film. Thus a triode deposited film is expected to exhibit different properties from that of the coventionally diode deposited film. Figure 1a shows exchange shift and hysteresis loop of a 200 Å NiFe film etched back to 150Å NiFe/100Å FeMn/50Å Ta triode deposited sheet films. Figure 1b is the loop on corresponding diode sputtered films. They have different exchange shifts and coercivities. Figures 2a and 2b are the TEM micrographs of films deposited in triode and diode sputtering systems respectively, showing their grain sizes. Variation in properties of these films will be associated with the grain size in this paper. Experimental results and physical arguments will be presented to show improvement in ordering temperature due to increased grain size in the antiferromagnetic film either through deposition method or through thermal treatment. Barkhausen noise was studied on triode sputtered films of antiferromagnetic exchange coupled (AEC) MR element in combination with soft adjacent layer (SAL) transverse biasing.