Etching Effect on Exchange Anisotropy in NiFe/Cu/NiFe/IrMn Spin-valve Structure for an Array of PHR Sensor Element

Ar ion beam etching was carried out on NiFe(6)/Cu(1.5)/NiFe(4)/IrMn(20) multilayer spin-valve structure with three different beam voltages in order to optimize the effective beam voltage for patterned planar Hall device fabrication. VSM characterizations were done on the multilayer structure before and after etching for verification of necessary exchange bias and influence of etching. The multilayer spin-valve structure exhibits exchange bias of 202 Oe for as deposited sample whereas it enhances to 314 Oe after etching for the etching beam voltage of 800 V. Similarly, the corresponding coercivity of the spin-valve structure before etchings is 113 Oe while it is increased to 179 Oe after ion beam etching. Ar ion beam etching was done for subsequent fabrication of patterned junctions of different dimensions of 50times50 mum², 20times20 mum² and 5times5 mum² using lithography. The PHE measurements were made on all three junctions. Sensitivity has bee found to be more as the size of the patterned junction becomes smaller and smaller.