Resistance as a reliability indicator in lifetime testing of thin film magnetic recording heads

It is demonstrated that the resistance rise observed during lifetime testin g of magnetoresistive heads is primarily due to interlayer diffusion of Ta into the Au, NiFe, and NiFeRh layers, not electromigration damage to the se nsor. 3.2 Gb/in.(2) production heads which were preannealed at 275 degrees C for 168 h without bias current prior to lifetime testing showed no increa se in resistance, or evidence of electromigration, after 200 h at 150 degre es C with a current density of 7.6x10(7) A/cm(2). In contrast, identical he ads, which were not preannealed, showed an average 14% resistance rise duri ng the same lifetime test. Step annealing of heads and sheet films of Cr/Co CrPt/Ta/Au/Ta and NiFeRh/Ta/NiFe/Ta showed that the resistance rise was lin ear in t(1/2), where t is the annealing time, in the earliest stages of the anneal cycle. This behavior is indicative of diffusion processes in the he ads. (C) 2000 American Institute of Physics. [S0021-8979(00)72608-9].