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Abstract For the dinuclear spin crossover [Fe(qsal)₂][Ni(dmit)₂] (where qsal N(8quinolyl) salicylaldimine and1,3-dithiol-2-thione-4,5-dithiolato) complex, elemental X-ray magnetic circular dichroism (XMCD) measurements at the Fe and NiX-ray absorption edges indicate anti-ferromagnetic alignment of the Fe and Ni. This anti-ferromagnetic alignment is consistent with theab initiocalculations performed using the DFT+Umethod. The DFT+Ucalculations indicate that while the moments residing in the Fe cation are localized on the metal, there is a significant delocalization of the spin density on the Ni(dmit)₂moiety, with considerable magnetic moment associated with the ligand. This placement of some moment on the dmit ligand explains the XMCD signal at photon energies well above the metal absorption edge. This dmit ligand moment is consistent with the large inverse photoemission signal that is most sensitive to the surface layer dmit, the known surface termination of [Fe(qsal)₂][Ni(dmit)₂]. The organic ligand clearly can mediate antiferromagnetic coupling between metal centers with significant separation. 

To investigate the paramagnetic correlation lengths by XMCD, in a polyaniline plus a spin crossover molecular complex, dilute concentrations of magnetic nickel cobaltite (NiCo₂O₄) nanoparticles were added to the bimolecular mixture. 

Adding Fe₃O₄nanoparticles to composites of [Fe(Htrz)₂(trz)](BF₄) spin-crossover polymer and polyaniline (PANI) drives a phase separation of both and restores the molecular structure and cooperative effects of the spin-crossover polymer without compromising the increased conductivity gained through the addition of PANI. We observe an increased on-off ratio for the DC conductivity owing to an enlarged off state resistivity and a 20 times larger AC conductivity of the on state compared with DC values. The Fe₃O₄nanoparticles, primarily confined to the [Fe(Htrz)₂(trz)](BF₄) phase, are ferromagnetically coupled to the local moment of the spin-crossover molecule suggesting the existence of an exchange interaction between both components. 

The example of spin crossover molecule [Fe(Htrz)2(trz)](BF4) (where Htrz = 1H-1,2,4-triazole) plus polyaniline composite thin films is used to illustrate the rapid improvement in transport properties signaling that competitive molecular devices for back end of the line (BEOL) silicon compatible nonvolatile memory arrays are increasing realistic. 

Abstract In this work, we provide clear evidence of magnetic anisotropy in the local orbital moment of a molecular thin film based on the SCO complex [Fe(H 2 B(pz) 2 ) 2 (bipy)] (pz = pyrazol−1−yl, bipy = 2,2′−bipyridine). Field dependent x-ray magnetic circular dichroism measurements indicate that the magnetic easy axis for the orbital moment is along the surface normal direction. Along with the presence of a critical field, our observation points to the existence of an anisotropic energy barrier in the high-spin state. The estimated nonzero coupling constant of ∼2.47 × 10 −5 eV molecule −1 indicates that the observed magnetocrystalline anisotropy is mostly due to spin–orbit coupling. The spin- and orbital-component anisotropies are determined to be 30.9 and 5.04 meV molecule −1 , respectively. Furthermore, the estimated g factor in the range of 2.2–2.45 is consistent with the expected values. This work has paved the way for an understanding of the spin-state-switching mechanism in the presence of magnetic perturbations. 

Abstract Using optical characterization, it is evident that the spin state of the spin crossover molecular complex [Fe{H 2 B(pz) 2 } 2 (bipy)] (pz = tris(pyrazol-1-1y)-borohydride, bipy = 2,2ʹ-bipyridine) depends on the electric polarization of the adjacent polymer ferroelectric polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) thin film. The role of the PVDF-HFP thin film is significant but complex. The UV–Vis spectroscopy measurements reveals that room temperature switching of the electronic structure of [Fe{H 2 B(pz) 2 } 2 (bipy)] molecules in bilayers of PVDF-HFP/[Fe{H 2 B(pz) 2 } 2 (bipy)] occurs as a function of ferroelectric polarization. The retention of voltage-controlled nonvolatile changes to the electronic structure in bilayers of PVDF-HFP/[Fe{H 2 B(pz) 2 } 2 (bipy)] strongly depends on the thickness of the PVDF-HFP layer. The PVDF-HFP/[Fe{H 2 B(pz) 2 } 2 (bipy)] interface may affect PVDF-HFP ferroelectric polarization retention in the thin film limit. 

Spin crossover complexes are a route toward designing molecular devices with a facile readout due to the change in conductance that accompanies the change in spin state. Because substrate effects are important for any molecular device, there are increased efforts to characterize the influence of the substrate on the spin state transition. Several classes of spin crossover molecules deposited on different types of surface, including metallic and non-metallic substrates, are comprehensively reviewed here. While some non-metallic substrates like graphite seem to be promising from experimental measurements, theoretical and experimental studies indicate that 2D semiconductor surfaces will have minimum interaction with spin crossover molecules. Most metallic substrates, such as Au and Cu, tend to suppress changes in spin state and affect the spin state switching process due to the interaction at the molecule–substrate interface that lock spin crossover molecules in a particular spin state or mixed spin state. Of course, the influence of the substrate on a spin crossover thin film depends on the molecular film thickness and perhaps the method used to deposit the molecular film. 

A chiral 3D coordination compound, [Gd 2 (L) 2 (ox) 2 (H 2 O) 2 ], arranged around a dinuclear Gd unit has been characterized by X-ray photoemission and X-ray absorption measurements in the context of density functional theory studies. Core level photoemission of the Gd 5p multiplet splittings indicates that spin orbit coupling dominates over j–J coupling evident in the 5p core level spectra of Gd metal. Indications of spin–orbit coupling are consistent with the absence of inversion symmetry due to the ligand field. Density functional theory predicts antiferromagnet alignment of the Gd 2 dimers and a band gap of the compound consistent with optical absorption.