Intracluster interactions in butterfly{Fe3LnO2}molecules with the non-Kramers ions Tb(III) and Ho(III)

Abstract

The intracluster exchange interactions within the "butterfly" [Fe 3 Ln(μ 3 -O) 2 (CCl 3 COO) 8 (H 2 O)(THF) 3 ] molecules, where Ln(III) represents a lanthanide cation, have been determined by a combination of x-ray magnetic circular dichroism (XMCD) and vibrating sample magnetometry (VSM) along with an interaction model. We have studied the compounds with Ln = Tb and Ho, both non-Kramers lanthanides and with high uniaxial anisotropy, and Ln = Lu(III) and Y(III) as pseudolanthanides, which supply nonmagnetic Ln reference cases. At low temperature, the three Fe atoms can be considered as a self-unit with total spin S Fe 3 = 5/2. Using the element selectivity of the XMCD magnetometry, measured at the Ln L 2,3 edges, together with the VSM measurements, the local magnetization of the Ln ion and the Fe 3 subcluster, as a function of the field and low temperature (T ≈ 2.5 K), has been determined separately. These results are described quantitatively in the framework of a theoretical model based on an effective spin Hamiltonian, which considers the competing effects of intracluster interactions and the external applied magnetic field. The Ln-Fe 3 exchange interaction within the {Fe 3 LnO 2 } cluster has been determined to be antiferromagnetic, in both Tb and Ho compounds, with J FeTb /k B = −0.13(1) K and J FeHo /k B = −0.18(1) K, respectively. In both cases, a field-induced reorientation of the Fe 3 and Ln spins from antiparallel to parallel orientation takes place at a threshold field μ 0 H = 1.1 and 2 T, for the {Fe 3 TbO 2 } and {Fe 3 HoO 2 } compounds, respectively. By comparison with other compounds of the series with uniaxial anisotropy, it is concluded that the polarizability of the Fe 3 subcluster magnetic moment decreases in the trend {Fe 3 YO 2 } → {Fe 3 TbO 2 } → {Fe 3 HoO 2 } → {Fe 3 DyO 2 }, because of the increasing opposition of the exchange antiferromagnetic field caused by the Ln ion. In the Ln = Tb, Ho, and Dy, the magnetization of the whole molecule is dominated by the anisotropy of the Ln ion. The intracluster Fe 3 -Ln exchange interactions are very weak compared to the Ln ligand field and Fe-Fe exchange interactions.

A Series of High‐nuclear 3d‐4f (FeIII8LnIII2) Complexes: Syntheses, Structures, and Magnetic Properties

“…The most attentions are focused on [Cu‐Ln], [Mn‐Ln] systems, and [Fe‐Ln] SMMs are less developed. In recent years, although there are a growing number of Fe III ‐Ln III systems have been certificated, comparatively a few of them have been characterized as SMMs . Thus, the design and synthesis of the Fe III ‐Ln III SMMs remains a great challenge.…”

Hard X-ray magnetochiral dichroism in a paramagnetic molecular 4f complex

“…At this edge, absorption of an incident X-ray photon promotes a 2p 3/2 core electron into empty 5d or 6s valence states via the allowed electric dipole transitions (Dl ¼ AE1) or to 6p or 4f states (Dl ¼ 0,+2) via electric quadrupole transitions. Such quadrupolar 2p-4f transitions are easily distinguishable either in X-ray MCD (XMCD) or in resonant inelastic X-ray scattering spectra at the L 3 -edge 64,65 of rare-earths, whereas their contribution at the L 2 -edge is more difficult to disentangle. 66 We used le (L) or right (R) circularly polarised X-rays whose wave vector, k, was parallel (+) or antiparallel (À) to the external magnetic eld, B.…”

A Metal‐Organic Framework Incorporating Eight Different Size Rare‐Earth Metal Elements: Toward Multifunctionality À La Carte

“…The above analysis of mCB-8RE is a beautiful example showing the power of element-selective XMCD technique to investigate the magnetic response of individual ions within a very complex material. In previous works in the literature, XMCD was used to study the magnetism of 2 or 3 three ions in intermetallics, [122,123] 3d-4f [124,125] or 4f-4f [126] clusters. In this work, it was possible to determine the spectroscopic and magnetic properties of up to eight different RE ions in mCB-8RE.…”