Detailed single crystal EPR lineshape measurements for the single molecule magnets Fe8Br and Mn12-ac

Abstract

It is shown that our multi-high-frequency (40-200 GHz) resonant cavity technique yields distortion-free high field EPR spectra for single crystal samples of the uniaxial and biaxial spin S = 10 single molecule magnets (SMMs) [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O and [Fe8O2(OH)12(tacn)6]Br8.9H2O. The observed lineshapes exhibit a pronounced dependence on temperature, magnetic field, and the spin quantum numbers (Ms values) associated with the levels involved in the transitions. Measurements at many frequencies allow us to separate various contributions to the EPR linewidths, including significant D-strain, g-strain and broadening due to the random dipolar fields of neighboring molecules. We also identify asymmetry in some of the EPR lineshapes for Fe8, and a previously unobserved fine structure to some of the EPR lines for both the Fe8 and Mn12 systems. These findings prove relevant to the mechanism of quantum tunneling of magnetization in these SMMs.

Phys. Rev. B, accepted with minor revisions

References in corpus (4)

• Effects of D-strain, g-strain, and dipolar interactions on EPR linewidths of the molecular magnets Fe8 and Mn12
• Spin tunneling via dislocations in Mn-12 acetate crystals
• Dislocation-induced spin tunneling in Mn-12 acetate
• Linewidth of single photon transitions in Mn${}_{12}$-acetate

Cited by in corpus (25)

• Definitive spectroscopic determination of the transverse interactions responsible for the magnetic quantum tunneling in Mn12-acetate
• S-mixing and quantum tunneling of the magnetization in molecular nanomagnets
• A rotating cavity for high-field angle-dependent microwave spectroscopy of low-dimensional conductors and magnets
• Exchange Interactions and High-Energy Spin States in Mn_12-acetate
• Photon-assisted tunneling in a Fe8 Single-Molecule Magnet
• Role of dipolar and exchange interactions in the positions and widths of EPR transitions for the single-molecule magnets Fe8 and Mn12
• Effect of extra electrons on the exchange and magnetic anisotropy in the anionic single-molecule magnet Mn12
• Evidence for the S=9 excited state in Mn12-bromoacetate measured by electron paramagnetic resonance
• Magnetization dynamics in the single-molecule magnet Fe8 under pulsed microwave irradiation
• Characterization of the S = 9 excited state in Fe8Br8 by Electron Paramagnetic Resonance
• Photon-Induced Magnetization Reversal in Single-Molecule Magnets
• Crystal lattice desolvation effects on the magnetic quantum tunneling of single-molecule magnets
• Collective coupling of a macroscopic number of single-molecule magnets with a microwave cavity mode
• Tunneling Splittings in Mn12-Acetate Single Crystals
• Second-order transverse magnetic anisotropy induced by disorders in the single-molecule magnet Mn12
• Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn${}_{12}$-Acetate and Fe${}_8$Br${}_8$
• Observation of a Distribution of Internal Transverse Magnetic Fields in a Mn12-Based Single Molecule Magnet
• Spin anisotropy effects in dimer single molecule magnets
• High frequency EPR on dilute solutions of the single molecule magnet Ni${}_4$
• Asymmetric Lineshape due to Inhomogeneous Broadening of the Crystal-Field Transitions in Mn12ac Single Crystals
• Phonon bottleneck in the low-excitation limit
• Spin-Orbit Coupling Fluctuations as a Mechanism of Spin Decoherence
• Order-of-Magnitude SNR Improvement for High-Field EPR Spectrometers via 3D-Printed Quasioptical Sample Holders
• EPR spectrum via entangled states for an Exchange-Coupled Dimer of Single-Molecule Magnets
• Effect of Defects on the Line shape of Electron Paramagnetic Resonance Signals from the Single-Molecule Magnet Mn12: A Theoretical Study