Method and test structure for determining magnetic domain switching field when fabricating patterned exchange biased magnetoresistive (MR) head

A method for determining a magnetic domain switching field comprising:

• providing a substrate;
• forming upon the substrate a patterned magnetoresistive (MR) layer, the patterned magnetoresistive (MR) layer having a projected length of the patterned magnetoresistive (MR) layer upon the substrate and a projected width of the patterned magnetoresistive (MR) layer upon the substrate;
• forming at a pair of separated locations over the patterned magnetoresistive (MR) layer a pair of patterned conductor lead layers, the pair of patterned conductor lead layers defining a track width of the patterned magnetoresistive (MR) layer, the track width of the patterned magnetoresistive (MR) layer being smaller than the projected width of the patterned magnetoresistive (MR) layer;
• forming upon the track width of the patterned magnetoresistive (MR) layer a minimum of one patterned anti-ferromagnetic layer separated from each patterned conductor lead layer within the pair of patterned conductor lead layers by a minimum of one unpinned width of the patterned magnetoresistive (MR) layer, the patterned magnetoresistive (MR) layer also having a minimum of one pinned width of the patterned magnetoresistive (MR) layer beneath the minimum of one patterned anti-ferromagnetic layer, where the pinned width of the patterned magnetoresistive (MR) layer and the unpinned width of the patterned magnetoresistive (MR) layer each have their magnetic domains ordered in a first direction absent an external magnetic field, and where the projected length of the patterned magnetoresistive (MR) layer, the unpinned width of the patterned magnetoresistive (MR) layer and the pinned width of the patterned magnetoresistive (MR) layer are chosen such that the magnetic domains within the unpinned width of the patterned magnetoresistive (MR) layer and the pinned width of the patterned magnetoresistive (MR) layer are coupled such that they switch jointly in an externally applied magnetic field gradient;
• exposing the substrate to an externally applied negative magnetic field gradient opposite the first direction of the magnetic domains within the pinned width of the patterned magnetoresistive (MR) layer and the unpinned width of the patterned magnetoresistive (MR) layer while measuring a first resistance change through the pair of patterned conductor lead layers to determine a first magnetic field strength at which the magnetic domains within the pinned width of the patterned magnetoresistive (MR) layer and the unpinned width of the patterned magnetoresistive (MR) layer switch jointly to a second direction opposite the first direction;
• and
• exposing the substrate to a positive magnetic field gradient opposite the second direction of the magnetic domains within the pinned width of the patterned magnetoresistive (MR) layer and the unpinned width of the patterned magnetoresistive (MR) layer while measuring a second resistance change through the pair of patterned conductor lead layers to determine a second magnetic field strength at which the magnetic domains within the pinned width of the patterned magnetoresistive (MR) layer and the unpinned width of the patterned magnetoresistive (MR) layer switch jointly to return to the first direction opposite the second direction.