Mössbauer spectroscopy of a monolayer of single molecule magnets

Abstract

The use of single molecule magnets (SMMs) as cornerstone elements in spintronics and quantum computing applications demands that magnetic bistability is retained when molecules are interfaced with solid conducting surfaces. Here, we employ synchrotron Mössbauer spectroscopy to investigate a monolayer of a tetrairon(III) (Fe4) SMM chemically grafted on a gold substrate. At low temperature and zero magnetic field, we observe the magnetic pattern of the Fe4 molecule, indicating slow spin fluctuations compared to the Mössbauer timescale. Significant structural deformations of the magnetic core, induced by the interaction with the substrate, as predicted by ab initio molecular dynamics, are also observed. However, the effects of the modifications occurring at the individual iron sites partially compensate each other, so that slow magnetic relaxation is retained on the surface. Interestingly, these deformations escaped detection by conventional synchrotron-based techniques, like X-ray magnetic circular dichroism, thus highlighting the power of synchrotron Mössbauer spectroscopy for the investigation of hybrid interfaces.

Light-Induced Excited Spin-State Trapping: A Methodological Approach

“…It was shown that this source, obtained by an extreme care in the collimation of the high photon flux of the synchrotron, a multi-step monochromatization and a refinement of the nuclear resonant monochromator obtained with a 57 FeBO3 single crystal combined with a grazing incidence geometry, allows to investigate thin films down to the single molecular layer. 61 Grazing incidence reflection occurs at the substrate surface, and the molecular layer produces absorption lines that can be treated as those obtained in a standard setup in transmission geometry by correcting the effective thickness of the samples to account for the path lengths of both the incident and reflected radiations inside the molecular layer.…”

Propeller‐Shaped Fe4 and Fe3M Molecular Nanomagnets: A Journey from Crystals to Addressable Single Molecules

“…The use of a collimated, highly focused and monochromatic beam generated by a 57 FeBO 3 crystal, acting as a secondary source excited by synchrotron‐radiation γ ‐rays, allowed to perform experiments at grazing incidence with a thousand‐fold increase in sensitivity . Using this exotic technique, the response of a monolayer of 57 Fe‐enriched 3 R chemisorbed on gold was detected [R = (CH 2 ) 5 SAc] . Figure shows the low‐temperature Mössbauer spectra of such a monolayer and of a bulk sample.…”

“…The velocity axis values are relative to the α‐Fe standard. Adapted from ref . Copyright 2018 The Authors.…”

Interplay of Spin and Spatial Anisotropy in Low-Dimensional Quantum Magnets with Spin 1/2

“…Besides bulk materials, the modification of their properties by a deposition of molecular-based magnets on substrates [119,120], growing in the confined geometry [121], etc. opens new possibilities for the experimental and theoretical investigations.…”