Persistent Spin Dynamics in the $S=1/2$ V$_{15}$ Molecular Nano-Magnet

TL;DR

This study investigates the persistent spin fluctuations in the V15 molecular nano-magnet at very low temperatures, revealing temperature-independent relaxation rates and spin dynamics driven by nuclear spin interactions.

Contribution

The paper provides the first muon spin relaxation measurements showing persistent spin dynamics in V15 down to 12 mK, highlighting the role of nuclear spin coupling.

Findings

Relaxation rate is temperature independent below 10 K.

Spin fluctuation time saturates at ~6 ns at low temperatures.

Spin dynamics are driven by coupling to nuclear spins.

Abstract

We present muon spin lattice relaxation measurements in the V15 spin 1/2 molecular nano-magnet. We find that the relaxation rate in low magnetic fields (<5 kG) is temperature independent below ~10 K, implying that the molecular spin is dynamically fluctuating down to 12 mK. These measurements show that the fluctuation time increases as the temperature is decreased and saturates at a value of ~6 nsec at low temperatures. The fluctuations are attributed to V15 molecular spin dynamics perpendicular to the applied magnetic field direction, induced by coupling between the molecular spin and nuclear spin bath in the system.