Integrated giant magnetoresistance bridge sensors with transverse permanent magnet biasing

Two types of giant magnetoresistance (GMR) multilayer bridge sensors with i ntegrated permanent magnet biasing are demonstrated. These sensors differ f rom previous designs where external permanent magnets were used. The bridge s consist of four active GMR multilayer elements at the first antiferromagn etic coupling peak of a NiFe/[NiFe/CoFe/Cu](10) structure (GMR=18%). Bridge linearization is obtained by creating opposite biasing fields of equal amp litude (+/- 200 Oe) in contiguous GMR elements of the bridge structure. Thi s is achieved either by using pairs of permanent magnets with the same Mrt value (14 memu/cm2) but different coercivities (type I bridge, H-c1=1400 Oe , H-c2=800 Oe), or by using a single type of permanent magnet and placing t he GMR sensor either under the magnet, or on its side (type II bridge). Lin ear ranges of +/- 200 Oe with field sensitivities of 0.3 mV/(VxOe) were obt ained in these bridges. (C) 2000 American Institute of Physics. [S0021-8979 (00)33008-0].