Determining Key Local Vibrations in the Relaxation of Molecular Spin Qubits and Single-Molecule Magnets

Abstract

Herein we develop a simple first-principles methodology to determine the modulation that vibrations exert on spin energy levels, a key for the rational design of high-temperature molecular spin qubits and single-molecule magnets. This methodology is demonstrated by applying it to [Cu(mnt)2] 2-(mnt 2-= 1,2-dicyanoethylene-1,2-dithiolate), a highly coherent complex, using DFT to calculate the normal vibrational modes and wave-function based theory calculations to estimate the spin energy level structure. By theoretically identifying the most relevant vibrational modes, we are able to offer general strategies to chemically design more resilient magnetic molecules, where the qubit energy is not coupled to local vibrations.

Slow Magnetic Relaxation in a Palladium–Gadolinium Complex Induced by Electron Density Donation from the Palladium Ion

“…[25,26] The direct process is favored in the low-T region, whereas the Orbach process is dominant at higher T. This agreesw ith the role of anharmonic phonons described by Sessoli et al, [46] but differs from the source of the phonon-spin interactions. The Pd-Gdv ibrational modes, which represents aunique metal-metal interaction intrinsic to the coordination geometry of 1,i sb elieved to be the origin of the phonon [47] rather than the crystal lattice, which Sessoli and coworkers [20] have reported for potential V-based molecular qubits. Although there are two relaxation peaks for 1,o nly one relaxation peak was observed for 3 and the frozen solutions.…”

First-Principles Investigation of Spin–Phonon Coupling in Vanadium-Based Molecular Spin Quantum Bits

“…[34,36] In order to correctly account for the vibrational properties of solid state systems, where intermolecular interactions become relevant, DFT calculations are performed in the crystal phase, in contrast to previous studies where the gas phase was taken into consideration. [34] The quality of our computed vibrational properties is ascertained by IR vibrational spectroscopy in the THz range. The information extracted from DFT and post Hartee-Fock methods together provide a fingerprint description of the interaction between vibrations and magnetism, and directly correlate to the structure of each compound.…”

Single‐Molecule Magnets DyM2N@C80 and Dy2MN@C80 (M=Sc, Lu): The Impact of Diamagnetic Metals on Dy3+ Magnetic Anisotropy, Dy⋅⋅⋅Dy Coupling, and Mixing of Molecular and Lattice Vibrations

“…They found that spin-phonon relaxationv ia anharmonic phonons may also result in Arrheniusb ehavior,b ut with the U eff corresponding to half of the vibrational frequency.F urthermore, other research teams analyzed the locality of the spin-phonon interaction and concluded that molecular vibrations spatially localized close to the metal center usually have the strongest contribution to the spin relaxation. [17,19] These findings show that the Debye model is oversimplified for the analysiso f spin-phonon relaxation in molecular magnets [20] and an analysis of the real vibrational spectra may give better insighti nto the relaxation mechanism. [21] With this in mind, we decided to analyze the low-frequency part of the vibrational spectra of the NCFs.…”