OXYGEN AS A SURFACTANT IN THE GROWTH OF GIANT MAGNETORESISTANCE SPIN VALVES

We have found a novel method for increasing the giant magnetoresistanc e (GMR) of Co/Cu spin valves with the use of oxygen. Surprisingly, spi n valves with the largest GMR are not produced in the best vacuum. Int roducing 5x10(-9) Ton (7x10(-7) Pa) into our ultrahigh vacuum depositi on chamber during spin-valve growth increases the GMR, decreases the f erromagnetic coupling between magnetic layers, and decreases the sheet resistance of the spin valves. It appears that the oxygen may act as a surfactant during film growth to suppress defects and to create a su rface which scatters electrons more specularly. Using this technique, bottom spin valves and symmetric spin valves with GMR values of 19.0% and 24.8%, respectively, have been produced. These are the largest val ues ever reported for such structures. (C) 1997 American Institute of Physics.