Steady - state thermal characteristics of AMR

Tape storage drives use lithographically deposited anisotropic magnetoresistive (AMR) sensors to read magnetic transitions written on tape. The read-back signal and the reliability of an AMR sensor are both affected by sensor temperature. Because current passes through the sensor, it is subject to joule heating, dependent on both the geometry of the sensor and the thermal conductivities of its material. Because of the resources required to build new sensors, the ability to predict the effects of dimensional changes on sensor temperature is important. This paper describes an analytical model and a three-dimensional finite element analysis (FEA) of the heat transfer for a shielded rectangular-sheet AMR sensor under joule heating over a range of sensor dimensions. The novel analysis consolidates the experimental and FEA data into a few parameters that make it possible to calculate the sensor temperature as a function of power for a wide range of geometries, thus assisting designers who need to set current limitations on the read elements of extant drives and to extrapolate to next-generation drives. We also evaluate the temperature of a sensor and the substrate in a drive, combining the heating from writers and readers. Heat flow away from the head substrate was found to be significantly higher when the tape is moving than when it is stationary, and a simple model is developed to describe the heat dissipation of the substrate as a function of tape velocity.