Magnetic Resonance Force Microscopy at milliKelvin Temperatures

Magnetic Resonance Force Microscopy (MRFM) combines the high spatial resolution of scanning probe microscopy with magnetic resonance techniques to measure the magnetic properties of samples using sub-attoNewton tip-sample forces. In contrast to conventional MRFM setups, our MRFM makes use of a SQUID based detection to measure the motion of the magnetically tipped cantilever, and a superconducting NbTiN transmission line to apply the spin-manipulating radio-frequency magnetic field. These innovations significantly reduce the heating of both the cantilever and the sample, and lower the operating temperature of the MRFM setup to only tens of milliKelvins. This feat was demonstrated by measuring the Korringa relation in copper down to 42 mK. The low operating temperatures open up the possibility to study a variety of condensed matter systems, such as LAO-STO, topological insulators, and iron-doped palladium. Furthermore, we have developed a theory describing the spin-induced dissipation of magnetic resonators, allowing us to experimentally determine the density and relaxation time of the dangling bonds on the surfaces of SiO2 and diamond, and to measure the density of electron spins associated to the N-centers in diamond.