Probing the Fluctuating Magnetic Field of Fe-Triazole Spin-Crossover Thin Layers with Nitrogen-Vacancy Centers in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-27 |
| Journal | ACS Nano |
| Authors | Isabel Cardoso Barbosa, Tim Hochdörffer, Juliusz A. Wolny, Dennis Loenard, Stefan Johansson |
| Institutions | University of Koblenz and Landau, Rheinland-PfÀlzische Technische UniversitÀt Kaiserslautern-Landau |
Abstract
Section titled âAbstractâThe magnetic properties of Fe<sup>II</sup> spin-crossover (SCO) complexes can be changed upon temperature variation, often exhibiting thermal hysteresis. Particularly interesting for magnetic-memory applications are thin layers of SCO complexes, where practical magnetic probing techniques are required. While conventional magnetometry on SCO complexes employs cryogenic temperatures, nitrogen-vacancy (NV) centers are quantum magnetometers that can operate at room temperature with high spatial resolution and magnetic-field sensitivity. In this work, we apply thin layers of Fe-triazole SCO complexes onto a single-crystal diamond with shallow NV centers and probe the fluctuating magnetic field. We combine a wide-field technique with temperature-dependent measurements of the NV centersâ longitudinal spin-relaxation time <i>T</i><sub>1</sub> and the decoherence time <i>T</i><sub>2</sub> to find that the complexes are paramagnetic in the investigated temperature range from 20 to 80 °C. We quantitatively describe the <i>T</i><sub>1</sub> time by a model considering the fluctuating magnetic field of the Fe<sup>II</sup> ions. While we see signatures of a local change in spin state in the <i>T</i><sub>1</sub> relaxometry data, apparent structural changes in the SCO material dominate the local magnetic environment of the NV centers. The results for the <i>T</i><sub>2</sub> time contrast the findings of the <i>T</i><sub>1</sub> times for the SCO complexes, which we attribute to different NV detection sensitivities toward Fe<sup>II</sup> and Fe<sup>III</sup> of the protocols. Our results on the magnetic properties of SCO materials highlight the capabilities of the NV center as a susceptible sensor for fluctuating magnetic fields. At the same time, spin switching of the complexes cannot be observed.