TRULY UNCOUPLED SPIN VALVE MATERIAL

SPIN VALVE MATERIALS HAVE GREAT APPLICATION POTENTIAL IN MAGNETORESISTIVE RANDOM ACCESS MEMORY (MRAM), TAPE OR DISK READ HEADS, AND MAGNETIC FIELD SENSORS. HOWEVER, POSITIVE COUPLING BETWEEN THE TWO MAGNETIC LAYERS IS ALWAYS PRESENT IN SO-CALLED "UNCOUPLED" SPIN VALVE MATERIALS TODAY AND PRESENTS A ROADBLOCK FOR THE WIDESPREAD USE OF THOSE MATERIALS. THIS COUPLING REDUCES THE EFFECTIVE ANISOTROPY FIELD FOR MRAM MEMORY CELLS, REDUCES FIELD SENSITIVITY FOR SENSORS, AND MAY PREVENT "SINGLE DOMAIN" BEHAVIOR IN SPIN VALVE DEVICES. POSITIVE COUPLING IS BELIEVED TO BE CAUSED BY CORRELATED ROUGHNESS OF THE INTERFACES OF THE MAGNETIC LAYERS THROUGH A DIPOLE-TO-DIPOLE COUPLING EFFECT. TO OBTAIN TRULY UNCOUPLED SPIN VALVE MATERIALS, RESEARCHERS ARE DEVELOPING A NUMBER OF APPROACHES TO CONTROL THE INTERFACE QUALITY AND FLATNESS, AND CRYSTAL ORIENTATION OF THE SPIN VALVE MATERIALS USING INDUSTRY-STANDARD EQUIPMENT. SOME OF THE PROPOSED APPROACHES MAY ALSO INDUCE A BENEFICIAL ANTIFERROMAGNETIC EXCHANGE COUPLING.