A Reversible Magnetic Switch by Minute Adsorption of Cu on Co Films

Adsorption of minute amounts of Cu onto Co films leads to unexpected magnetic phenomena: Cu coverages as small as three hundredths of an atomic layer are sufficient to rotate the magnetization direction by 90 deg. in Co films up to 20 atomic layers thick. In other words, per single Cu atom, on average, the spins of more than 500 Co atoms switch. Additional Cu coverage, however, rotates the magnetization back to its original direction. As the magnetization changes discontinuously between two discrete states, a Cu-covered Co film can be regarded as a local magnetic switch. We demonstrate the feasibility of magnetic microstructuring by manipulating structural and magnetic properties locally.