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The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1). [ABSTRACT FROM AUTHOR]

The spin dynamics of Cr8Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities. [ABSTRACT FROM AUTHOR]

A magnetic Co‐production: The complex [Co(μ‐L)(μ‐OAc)Y(NO3)2] (see structure O red, N blue, C gray), in which the CoII ion exhibits a D value of approximately +45 cm−1, as determined by magnetic and inelastic neutron scattering experiments, exhibits slow magnetic relaxation and single‐ion magnet behavior. [ABSTRACT FROM AUTHOR]

The molecular wheel [Cr 10 (OMe) 20 (O 2 CCMe 3 ) 10 ], abbreviated {Cr 10 }, with an unusual intermediate total spin S = 9 and non-negligible cluster anisotropy, D / k B = -0.045(2) K, is a rare case among wheels based on an even number of 3d-metals, which usually present an antiferromagnetic (AF) ground state ( S = 0). Herein, we unveil the origin of such a behavior. Angular magnetometry measurements performed on a single crystal confirmed the axial anisotropic behavior of {Cr 10 }. For powder samples, the temperature dependence of the susceptibility plotted as χ T ( T ) showed an overall ferromagnetic (FM) behavior down to 1.8 K, whereas the magnetization curve M ( H ) did not saturate at the expected 30 μ B /fu for 10 FM coupled 3/2 spin Cr 3+ ions, but to a much lower value, corresponding to S = 9. In addition, the X-ray magnetic circular dichroism (XMCD) measured at high magnetic field (170 kOe) and 7.5 K showed the polarization of the cluster moment up to 23 μ B /fu. The magnetic results can be rationalized within a model, including the cluster anisotropy, in which the {Cr 10 } wheel is formed by two semiwheels, each with four Cr 3+ spins FM coupled ( J FM / k B = 2.0 K), separated by two Cr 3+ ions AF coupled asymmetrically ( J 23 / k B = J 78 / k B = -2.0 K; J 34 / k B = J 89 / k B = -0.25 K). Inelastic neutron scattering and heat capacity allowed us to confirm this model leading to the S = 9 ground state and first excited S = 8. Single-molecule magnet behavior with an activation energy of U / k B = 4.0(5) K in the absence of applied field was observed through ac susceptibility measurements down to 0.1 K. The intriguing magnetic behavior of {Cr 10 } arises from the detailed asymmetry in the molecule interactions produced by small-angle distortions in the angles of the Cr-O-Cr alkoxy bridges coupling the Cr 3+ ions, as demonstrated by ab initio and density functional theory calculations, while the cluster anisotropy can be correlated to the single-ion anisotropies calculated for each Cr 3+ ion in the wheel.

[This corrects the article DOI: 10.1039/C8SC00163D.].

The Cr 7 Co ring represents a model system to understand how the anisotropy of a Co II ion is transferred to the effective anisotropy of a polymetallic cluster by strong exchange interactions. Combining sizeable anisotropy with exchange interactions is an important point in the understanding and design of new anisotropic molecular nanomagnets addressing fundamental and applicative issues. By combining electron paramagnetic resonance and inelastic neutron scattering measurements with spin Hamiltonian and ab initio calculations, we have investigated in detail the anisotropy of the Co II ion embedded in the antiferromagnetic ring. Our results demonstrate a strong and anisotropic exchange interaction between the Co and the neighbouring Cr ions, which effectively transmits the anisotropy to the whole molecule.

CeCuAl 3 crystallizing in the tetragonal BaNiSn 3 -type structure and CeCu x Al 4-x solid solutions were investigated by means of elastic and inelastic neutron scattering. Powder neutron diffraction brought information on both temperature evolution of crystallographic parameters and magnetic order at low temperatures. No structural change was observed in the investigated temperature range from 1.5 to 300 K. Weak magnetic peaks outside nuclear Bragg positions observed in solid solutions with 0.90 ≤ x ≤ 1.10 were described by the propagation vector k = (0.40 + δ x , 0.60 + δ y , 0), where δ x ≈ 0.02 and δ y ≈ 0.01. The magnetic structure of CeCu 0.75 Al 3.25 consists of two components: an anti-ferromagnetic one described by the same k and a ferromagnetic one with k 0 = (0, 0, 0) and magnetic moments lying within the tetragonal basal plane. The evolution of magnetic excitations as a function of Cu-Al concentration in CeCu x Al 4-x was studied by inelastic neutron scattering. The measured spectra of CeCuAl 3 and the solution with x = 0.95 point to a three-magnetic-peak energy scheme, while only two excitations are expected from the local symmetry conditions on Ce atoms. The standard two-peak spectrum of crystal electric field excitations was observed for Cu-Al substitutions further from the 1:1:3 stoichiometry (x = 0.75 and 1.10). The intermediate concentrations (x = 0.90 and 1.05) exhibit spectra on the border between the former cases with a less clear pronounced first inelastic magnetic peak. The observed behavior is discussed considering the evolution of structural parameters in the CeCu x Al 4-x system and the coupling between the lattice vibrations and the crystal electric field excitations.