Magnetic tunnel junctions thermally stable to above 300 °C

Magnetic tunnel junctions formed from sandwiches of magnetically hard Co75Pt12Cr13 and magnetically soft Co88Pt12 ferromagnetic layers separated by thin alumina tunnel barriers are shown to be thermally stable to temperatures in excess of 300 degrees C. A comparison of cross-section transmission electron micrographs of an untreated sample and a similar one annealed at 350 degrees C indicates that the thickness of the amorphous tunnel barrier is slightly decreased after annealing. The resistance and magnetoresistance are only slightly affected by annealing at temperatures of up to similar to 300 degrees C but then decrease monotonically at higher annealing temperatures. Interaction of the alumina layer with the adjacent ferromagnetic layers is the likely cause of this decrease. (C) 1999 American Institute of Physics. [S0003-6951(99)01229-2].