Determination of the Distributions of the Spin-Hamiltonian Parameters in Spin Triangles: A Combined Magnetic Susceptometry and Electron Paramagnetic Resonance Spectroscopic Study of the Highly Symmetric [Cr3O(PhCOO)6(py)3](ClO4)·0.5py

Matrix effects on the magnetic properties of a molecular spin triangle embedded in a polymeric film

Molecular triangles with competing Heisenberg interactions and significant Dzyaloshinskii-Moriya interactions (DMI) exhibit high environmental sensitivity, making them potential candidates for active elements for quantum sensing. Additionally, these triangles exhibit magnetoelectric coupling, allowing their properties to be controlled using electric fields. However, the manipulation and deposition of such complexes pose significant challenges. This work explores a solution by embedding iron-based molecular triangles in a polymer matrix, a strategy that offers various deposition methods. We investigate how the host matrix alters the magnetic properties of the molecular triangle, with specific focus on the magnetic anisotropy, aiming to advance its practical applications as quantum sensors.

Search for Toroidal Ground State and Magnetoelectric Effects in Molecular Spin Triangles with Antiferromagnetic Exchange

Using first-principles methods and spin models, we investigate the magnetic properties of transition-metal trimers Cr₃ and Cu₃. We calculate exchange coupling constants and zero-field splitting parameters using density functional theory and, with these parameters, determine the ground spin state as well as thermodynamic properties via spin models. Results for Cr₃ indicate uniaxial magnetic anisotropy with a magnetic easy axis aligned along the 3-fold rotational symmetry axis and a mostly isotropic exchange interaction. The Cu₃ molecule lacks rotational symmetry and our results show strong antisymmetric interactions for three distinct exchange couplings within the molecule. We are able to reproduce experimental findings on magnetic susceptibility and magnetization of Cr₃ with the first-principles spin-Hamiltonian parameters. Our results show no presence of a toroidal ordering of spins for Cr₃ and a finite toroidal moment for Cu₃ in the ground state. We apply an external electric field up to 0.08 V/Å to each system to reveal the field dependence of exchange coupling as magnetoelectric effects. Finally, we scan the parameter space of a spin Hamiltonian to gain insights into which parameters would lead to a sizable toroidal moment in such systems.

Observation and deconvolution of a unique EPR signal from two cocrystallized spin triangles

A 16-line pattern has been theoretically predicted, but hitherto not reported, for the Electron Paramagnetic Resonance (EPR) spectrum of antiferromagnetically coupled CuII triangles experiencing isotropic exchange of isosceles magnetic symmetry. Now, the crystallization of such a triangular species and its X-ray structure determination in a polar space group, R3 (No. 146), has enabled its single crystal EPR study. Its detailed magnetic susceptibility, and X- and Q-band, powder and single crystal EPR spectroscopic study reveals the effect of molecular structure and of Dzyaloshinskii-Moriya interactions (DMI) on the g‖, g⊥ and A‖ parameters of the spectrum; DMI is considered for the first time in such a context. Moreover, careful analysis of the spectrum allows the deconvolution of two slightly different cocrystallized magnetic species.

Structural and Magnetical Studies of Mixed-Valence Hexavanadate Hybrids: How Organic Ligands Affect the Magnetism of Polyoxometalates?

In this Communication, we illustrate the influence of organic ligands on magnetic structure and behavior by employing a mixed-valence Lindqvist-type hexavanadate as a research platform. Through covalently attaching to different halogen-containing organic ligands, the derived hybrid materials have different magnetism compared to their parent structure. Single-crystal X-ray analyses show that the introduction of organic ligands can modify the crystal packing manners of the derivatives, leading to further changes of the interaction between magnetic units. This work demonstrates that organic functionalization can remarkably affect the magnetism of polyoxometalates by adjusting the distance and location of the magnetic fractions.

Half-Integer Spin Triangles: Old Dogs, New Tricks

Spin triangles, that is, triangular complexes of half-integer spins, are the oldest molecular nanomagnets (MNMs). Their magnetic properties have been studied long before molecular magnetism was delineated as a research field. This Review presents the history of their study, with references to the parallel development of new experimental investigations and new theoretical ideas used for their interpretation. It then presents an indicative list of spin-triangle families to illustrate their chemical diversity. Finally, it makes reference to recent developments in terms of theoretical ideas and new phenomena, as well as to the relevance of spin triangles to spintronic devices and new physics.

Supramolecular Assemblies of Trinuclear Copper(II)-Pyrazolato Units: A Structural, Magnetic and EPR Study

Two anionic complexes, {[Cu3(µ3-OH)(µ-4-Ph-pz)3Cl3]2[Cu(4-Ph-pzH)4](µ-Cl)2}2− (1) and [Cu3(µ3-OH)(µ-pz)3(µ1,1-N3)2(N3)]− (2), crystallize as one-dimensional polymers, held together by weak Cu-(µ-Cl) and Cu-(µ-N3) interactions, respectively. Variable temperature magnetic susceptibility analyses determined the dominant antiferromagnetic intra-Cu3 exchange parameters in the solid state for both complexes, whereas the weak ferromagnetic inter-Cu3 interactions manifested also in the solid state EPR spectra, are absent in the corresponding frozen solution spectra. DFT calculations were employed to support the results of the magnetic susceptibility analyses.

Relevance of Dzyaloshinskii–Moriya spectral broadenings in promoting spin decoherence: a comparative pulsed-EPR study of two structurally related iron(iii) and chromium(iii) spin-triangle molecular qubits

Two related iron(iii) and chromium(iii) spin-triangle molecular qubits show coherent driving of their spins, and decoherence that is not significantly affected by Dzyaloshikskii–Moriya spectral broadenings.