Probing the Nuclear Spin-Lattice Relaxation Time at the Nanoscale

Abstract

Nuclear spin-lattice relaxation times are measured on copper using magnetic resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxide interfaces, topological insulators and other strongly correlated electron systems such as high-Tc superconductors.Comment: We revised the manuscript by including the supplemental material. The manuscript is changed from a Letter to a Research Article after change of journa

Mechanical Generation of Radio-Frequency Fields in Nuclear-Magnetic-Resonance Force Microscopy

“…For copper, the relaxation time follows the Korringa relation [21] TT 1 ¼ 1.2 sK, which is confirmed in the experiments with the rf wire as the rf source [11]. After a saturation pulse ending at t ¼ 0, the frequency shift evolves as a function of time ΔfðtÞ according to…”

“…The dashed vertical lines are the indicated positions of the 8th and 9th mode of the cantilever. Visible in blue is that we obtain a much larger signal when the radio frequency applied corresponds to the 8th mode, which we attribute to a much larger B rf field, since the resonant slice thickness grows at sufficiently large rf field strengths [11].…”

“…(7), after applying a 1-s pulse with the rf wire [11], at a temperature of 42 mK. We use a current of I ¼ 0.2 mA, resulting in an alternating rf field of B rf ¼ ðμ 0 I=2πrÞ≈ 5.8 μT.…”

“…A detailed description of the setup can be found in Refs. [8,11]. Here, we will only give a short summary.…”

“…Our experimental setup and sample have been used recently to show that the nuclear spin-lattice relaxation time (T 1 ) of a copper sample can be probed at a nanoscopic scale [11] at spin temperatures as low as 42 mK. We used a superconducting rf wire to saturate 63 Cu and 65 Cu spins, causing a detectable frequency shift on the magnetic cantilever.…”