Pressure dependence of the magnetoresistance oscillations spectrum of beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF

The pressure dependence of the interlayer magnetoresistance of the quasi-two dimensional organic metal beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF has been investigated up to 1 GPa in pulsed magnetic fields up to 55 T. The Shubnikov-de Haas oscillations spectra can be interpreted on the basis of three compensated orbits in all the pressure range studied, suggesting that the Fermi surface topology remains qualitatively the same as the applied pressure varies. In addition, all the observed frequencies, normalized to their value at ambient pressure, exhibit the same sizeable pressure dependence. Despite this behavior, which is at variance with that of numerous charge transfer salts based on the BEDT-TTF molecule, non-monotonous pressure-induced variations of parameters such as the scattering rate linked to the various detected orbits are observed.Comment: accepted for publication in Phys. Rev.

De Haas-van Alphen oscillations in the compensated organic metal alpha-'pseudo-kappa'-(ET)4H3O[Fe(C2O4)3].(C6H4Br2)

Field-, temperature- and angle-dependent Fourier amplitude of de Haas-van Alphen (dHvA) oscillations are calculated for compensated two-dimensional (2D) metals with textbook Fermi surface (FS) composed of one hole and two electron orbits connected by magnetic breakdown. It is demonstrated that, taking into account the opposite sign of electron and hole orbits, a given Fourier component involves combination of several orbits, the contribution of which must be included in the calculations. Such FS is observed in the strongly 2D organic metal alpha-'pseudo-kappa'-(ET)4H3O[Fe(C2O4)3].(C6H4Br2), dHvA oscillations of which have been studied up to 55 T for various directions of the magnetic field with respect to the conducting plane. Calculations are in good quantitative agreement with the data.Comment: European Physical Journal B (2014

Multi-Magnetic Properties of a Novel SCO [Fe(3-OMe-Sal2trien)]-[Fe(tdas)2]·CH3CN Salt

The multi‐magnetic salt [Fe(3‐OMe‐Sal2trien)][Fe(tdas)2]·CH3CN (1) has been prepared and fully characterized by a variety of methods. The crystal structure of 1, determined at 150, 297 and 350 K, consists of alternating layers composed by a parallel arrangement of the chains of isolated π–π coupled cation pairs of [Fe(3‐OMe‐Sal2trien)]+ and anion pairs of [Fe(tdas)2]–. The complex magnetic behavior of this salt is consistent with the sum of the contributions from spin‐crossover (SCO) cations and strong antiferromagnetically (AFM) coupled dimeric [Fe(tdas)2]22– anions. The observed gradual thermally induced spin transition (T1/2 = 195 K) is relatable to the cation exhibiting disordering of ethylene (–CH2–CH2–) groups between two conformers with a narrow thermal hysteresis of 6 K. The dc magnetization measurements and 57Fe Mössbauer spectroscopy at room temperature are in excellent agreement between γHS(%) value and ratio of disordering of ethylene groups obtained from X‐ray analysis. Mössbauer spectra at 80 K and 296 K indicate a spin transition between S = 1/2 and S = 5/2 for the iron(III) saltrien‐cation and confirms S = 3/2 for the [FeIII(tdas)2]– anion. The experimental results are supplemented with a theoretical Density Functional Theory (DFT) analysis

Cyano-Bridged Dy(III) and Ho(III) Complexes with Square-Wave Structure of the Chains

Four new cyano-bridged DyIII-CrIII, DyIII-FeIII, HoIII-CrIII and HoIII-FeIII bimetallic coordination polymers were synthesized by the reaction of [Ln(H2dapsc)(H2O)4](NO3)3 (Ln = Dy, Ho); H2dapsc = 2,6-diacetylpyridinebis(semicarbazone)) with K3[M(CN)6] (M = Cr, Fe) in H2O, resulting in the substitution of two water molecules in the coordination sphere of rare earth by paramagnetic tricharged hexacyanides of Fe and Cr. The complexes are isostructural and consist of alternating [Ln(H2dapsc)(H2O)2]3+ and [M(CN)6]3− units linked by bridges of two cis-cyano ligands of the anion to form square-wave chains. The ac magnetic measurements revealed that the DyCr and DyFe complexes are field-induced single molecule magnets, while their Ho analogs do not exhibit slow magnetic relaxation

A Series of Field-Induced Single-Ion Magnets Based on the Seven-Coordinate Co(II) Complexes with the Pentadentate (N3O2) H2dapsc Ligand

A series of five new mononuclear pentagonal bipyramidal Co(II) complexes with the equatorial 2,6-diacetylpyridine bis(semicarbazone) ligand (H2dapsc) and various axial pseudohalide ligands (SCN, SeCN, N(CN)2, C(CN)3, and N3) was prepared and structurally characterizated: [Co(H2dapsc)(SCN)2]∙0.5C2H5OH (1), [Co(H2dapsc)(SeCN)2]∙0.5C2H5OH (2), [Co(H2dapsc)(N(CN)2)2]∙2H2O (3), [Co(H2dapsc)(C(CN)3)(H2O)](NO3)∙1.16H2O (4), and {[Co(H2dapsc)(H2O)(N3)][Co(H2dapsc)(N3)2]}N3∙4H2O (5). The combined analyses of the experimental DC and AC magnetic data of the complexes (1–5) and two other earlier described those of this family [Co(H2dapsc)(H2O)2)](NO3)2∙2H2O (6) and [Co(H2dapsc)(Cl)(H2O)]Cl∙2H2O (7), their theoretical description and the ab initio CASSCF/NEVPT2 calculations reveal large easy-plane magnetic anisotropies for all complexes (D = + 35 − 40 cm−1). All complexes under consideration demonstrate slow magnetic relaxation with dominant Raman and direct spin–phonon processes at static magnetic field and so they belong to the class of field-induced single-ion magnets (SIMs)

New insights on frequency combinations and 'forbidden frequencies' in de Haas-van Alphen spectrum of κ-(ET) 2 Cu(SCN) 2

Accepted in Journal of Physics: Condensed Matter (2016)De Haas-van Alphen oscillations of the organic metal κ-(ET) 2 Cu(SCN) 2 have been measured up to 55 T at liquid helium temperatures. The Fermi surface of this charge transfer salt is a textbook example of linear chain of orbits coupled by magnetic breakdown. Accordingly, the oscillation spectrum is composed of linear combinations of the frequencies linked to the α and magnetic breakdown-induced β orbits. The field and temperature dependence of all the observed Fourier components, in particular the 'forbidden frequency' β − α which cannot correspond to a classical orbit, are quantitatively accounted for by analytical calculations based on a second order development of the free energy, i.e. beyond the first order Lifshitz-Kosevich formula