Spin-polarized AFM on single spins

ESR-STM is a powerful tool for the quantum coherent control of spins on surfaces. However, for ESR- STM Spins should be isolated from metallic substrate. STM allows tunneling through 1-4 ML of insulating film such as MgO, NaCl, KBr etc. The thickness of decoupled layer and tunneling current determine the quantum coherent times (T1 and T2). On the other hand Spins on Insulators will provide longer quantum coherent times. To measure spins on insulators, ESR-AFM is an alternative tool, because AFM is accessible to spins on insulators, and magnetic exchange force microscopy has spin sensitivity at the atomic scale. To extend the single spin detection capability on insulator surface, we developed the spin-polarized AFM at center for quantum nanoscience (QNS) in south Korea, and it has been used to measure the single spin forces acting on the magnetic tip. STM needs only atomically sharp metal needle to sense the tunneling current but AFM needs more complicated sensor which measures atomics force. We uses a single pronged tuning fork as a force sensor, which vibrates at a given frequency naturally all the time without any interaction. Once the atomic force is applied to the sensor, the natural frequency is changed proportional to the magnitude of the force. When metal needle is used as an AFM tip, we can operate AFM and STM simultaneously. In My Talk I will talk about magnetic exchange force detection of single spin on MgO Surface and the transport measuremnt of Atomic gold wires on Si-553 surface.