Sensor properties of a robust giant magnetoresistance material system at elevated temperatures

The temperature dependence of the giant magnetoresistance (GMR) ratio, resi stance and exchange-biasing field for a spin valve comprising an Ir19Mn81-b iased artificial antiferromagnet (AAF) has been studied up to 325 degrees C . Up to 200-250 degrees C the temperature effects are reversible, at higher temperatures gradual irreversible changes are observed, probably due to at omic diffusion. The magnetoresistance effect is even at 200 degrees C still higher than for anisotropic magnetoresistance sensors at room temperature. The resistance of the multilayer shows a maximum around 250 degrees C. We found that this is due to the peculiar behavior of Ir-Mn, which has a negat ive temperature coefficient of the resistance. This provides a possibility to tune the temperature coefficient for the complete multilayer by varying the thickness of the Ir-Mn layer. The relative decrease of the exchange-bia sing field as a function of temperature is much smaller for spin valves wit h AAF than for conventional spin valves (without AAF). Furthermore, it was demonstrated that the GMR ratio can be increased to 12% at room temperature by using a dual spin valve with two AAFs. (C) 2000 American Institute of P hysics. [S0021-8979(00)49008-0].