Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures

TL;DR

This paper demonstrates Magnetic Resonance Force Microscopy at millikelvin temperatures using a SQUID-based detection method, enabling detection of paramagnetic spins on silicon surfaces and revealing spin diffusion effects at ultra-low temperatures.

Contribution

It introduces a novel MRFM technique operating at 30 mK with SQUID-based cantilever detection, enabling sensitive spin detection without overheating.

Findings

Successful MRFM operation at 30 mK

Detection of paramagnetic centers on silicon surfaces

Evidence of spin diffusion influencing low-temperature spin dynamics

Abstract

Magnetic Resonance Force Microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force-detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here, we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed SQUID-based cantilever detection technique which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centers on a silicon surface down to millikelvin temperatures. Fluctuations of such kind of defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs as well as in several superconducting and single spin qubits. We find evidence that spin diffusion plays a key role in the low temperature spin dynamics.