Tuning the Magnetic Properties of the High-Spin Molecular Cluster Fe8

Detailed single-crystal EPR line shape measurements for the single-molecule magnetsFe8BrandMnHill1, Maccagnano2, Park3 et al. 2002Phys. Rev. B1188771View full textAdd to dashboardCite

“…refs [8,31,32,33,34]). Careful consideration concerning the coupling of radiation to and from the cavity (via waveguide), combined with the ability to study very small samples, eliminates problems associated with standing waves in the sample probe [52].…”

“…Several EPR (and INS) experiments have indicated the presence of significant fourth order single-ion transverse anisotropies for both Mn 12 − ac [16,26,32,35] and Fe 8 Br [33,35]. Nevertheless, fourth order anisotropy cannot fully explain the observed spacing in magnetic field of magnetization steps observed in low temperature hysteresis experiments [49], and there remains considerable disagreement as to the magnitude of the fourth order terms [16,26,32,33,34,35,51]. Consequently, higher resolution EPR measurements are neces-sary in order to refine estimates of the Hamiltonian parameters, and to determine whether EPR lineshapes contain additional information concerning the MQT phenomenon.…”

“…In particular, this technique leads to at least a three orders of magnitude improvement in detection sensitivity [28] relative to conventional single-pass multi-high-frequency EPR techniques [8,31,32,33,34,35,36], which opens up many new avenues for probing SMMs. To date, our single crystal investigations have focused primarily on the energy dependence of the positions in magnetic field of EPR absorptions corresponding to transitions between different spin quantum levels [26,27,28,29].…”

“…It is commonly stated that observed EPR lineshapes cannot be analyzed because they contain uncontrollable distortions due to instrumental artifacts resulting from standing waves in the sample probe, which cause a mixing of the dissipative and reactive sample response [32,33,38]. This is most pronounced in the case of the high magnetic field studies of Barra et al [8,32,33,34]; asymmetric lineshapes are generally observed, making it extremely difficult to evaluate the true resonance positions. Indeed, even for aligned polycrystals, significant discrepancies can be noted between the observed and calculated EPR transitions, with respect to both the peak positions and intensities, as well as the line shapes and widths [33].…”

Hexacyanometalate molecular chemistry: trinuclear CrNi 2 complexes; micro-SQUID magnetisation studies of intermolecular interactions

“…The search for new polynuclear molecules displaying high spin ground state and anisotropy raises the interest of synthetic chemists [1,2,3,4,5,6] and physicists [7,8,9] involved in the field of molecular magnetism [10,11]. These anisotropic high spin molecules exhibit original magnetic properties such as single molecule magnet behaviour [12,13,14,15,16,17] (long relaxation time for the magnetisation below a so-called blocking temperature, T B ) or magnetic quantum tunnelling effect [18,19].…”