Thermal stability, sensitivity, and noise characteristics of MgO-based magnetic tunnel junctions (invited)

Thermal stability, sensitivity, and noise of micron-scale magnetic tunnel junctions based on MgO tunnel barriers have been studied for both the memory and sensing configurations. Junctions show solid high-temperature performance with substantial magnetoresistance observed even at 500°C. At temperatures above 375°C, the junctions begin to experience irreversible degradation due to interlayer diffusion. The thermal stability of these devices depends strongly on the exchange bias of the device and hence on the properties of the antiferromagnetic layer. Sensitivities as high as 3.3%∕Oe have been obtained at room temperature for junctions configured as low-field sensors. Sensitivity values are constant up to temperatures of 300°C, above which performance decays due to a loss of exchange bias and overall magnetoresistance. Noise spectra are 1∕f at frequencies up to 51kHz, and sensors have a resultant field noise better than 1nT∕Hz0.5 at 100kHz. A comparison is made with devices fabricated with alumina tunnel barriers.