SPIN VALVES USING AMORPHOUS MAGNETIC LAYERS

The giant magnetoresistance (GMR) effect is reported for spin valves u sing very thin amorphous (a-) magnetic layers. Two kinds of spin valve structures have been examined, one an a-CoFeB/Cu/Co sandwich and the other an a-CoFeB/Cu/a-CoFeB/NiO spin valve. In the Co/Cu/a-CoFeB sandw ich, the maximum MR ratio was obtained at the thickness of the amorpho us layer of 2 nm. In a-CoFeB/Cu/a-CoFeB/NiO spin valves, the maximum M R ratio was also obtained at the thickness of the free amorphous layer of 2 nm, slightly decreasing at a thickness of 6 nm, although the ant iparallel magnetization configuration was still satisfied. This demons trates that amorphous magnetic alloys are favorable for making very th in spin valves in spite of the short mean free path of the conduction electrons.