LOOSE SPINS IN FE CU FE(001) STRUCTURES

Slonczewski recently proposed a model for the exchange coupling betwee n ferromagnetic layers separated by a nonferromagnetic spacer based on the concept of ''loose spins'' ''Loose spins'' contribute to the tota l exchange energy. We have studied the role of ''loose spins'' in bcc Fe/Cu/Fe(001) structures. bcc Fe/Cu/Fe(001) trilayers deposited at roo m temperature were investigated extensively in our previous studies. I n our ''loose spin'' studies, the Fe was added inside the Cu interlaye r. Several structures were atomically engineered in order to test the behavior of ''loose spins:'' One additional atomic layer of an (Fe+Cu) alloy were located in appropriate positions in a Cu spacer. The bilin ear and biquadratic exchange coupling in the above structures was quan titatively studied with FMR in the temperature range 77-370 K and with MOKE at RT.