Study of the local field distribution on a single-molecule magnet-by a single paramagnetic crystal; a DPPH crystal on the surface of an Mn12-acetate crystal

TL;DR

This study investigates the local magnetic field distribution on a single-molecule magnet surface using EPR spectroscopy with a DPPH probe, revealing temperature-dependent broadening effects related to spin interactions.

Contribution

It introduces a simple EPR-based method to analyze local magnetic fields on SMM surfaces using a DPPH probe, providing new insights into spin interactions at various temperatures.

Findings

DPPH EPR spectra show broadening and shifting due to the SMM surface.

Broadening attributed to dipolar and exchange interactions.

Temperature dependence of local magnetic field distribution was characterized.

Abstract

The local magnetic field distribution on the subsurface of a single-molecule magnet crystal, SMM, above blocking temperature (T >> Tb) detected for a very short time interval (~ 10-10 s), has been investigated. Electron Paramagnetic Resonance (EPR) spectroscopy using a local paramagnetic probe was employed as a simple alternative detection method. An SMM crystal of [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O (Mn12-acetate) and a crystal of 2,2- diphenyl-1-picrylhydrazyl (DPPH) as the paramagnetic probe were chosen for this study. The EPR spectra of DPPH deposited on Mn12-acetate show additional broadening and shifting in the magnetic field in comparison to the spectra of the DPPH in the absence of the SMM crystal. The additional broadening of the DPPH linewidth was considered in terms of the two dominant electron spin interactions (dipolar and exchange) and the local magnetic field distribution on the crystal surface. The temperature dependence of the linewidth of the Gaussian distribution of local fields at the SMM surface was extrapolated for the low temperature interval (70-5 K).