Infrared Spectroscopy under high magnetic field and its application to molecular conducto

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In this research project, we aim to study optical properties of molecular conductors under high magnetic field. For this purpose, we constructed a new spectrometer and by use of that we have recently succeeded to measure the reflection spectra of a molecular conductor under the magnetic field of 9.6 T in Voigt configuration. This is the first reflectivity measurement under high magnetic field for molecular conductors.The measurements have been done for θ-(BEDT-TTF)_2CsZn (SCN)_4 (the sample size 0.4 mm×2 mm ; platelet). This salt exhibits metal-insulator transition around 20 K.When the magnetic field is not applied, the reflectance spectra at 8 K are almost the same as those at 25 K.Under the magnetic field of 9.6 T, the reflectivity below 2000 cm^<-1> increases at 25 K, while such increase is negligible at 8 K.We concluded that the increase of reflectivity at 25 K is probably due to the suppression of magnetic fluctuation by the magnetic field.In connection with the research project, we have done several studies for molecular conductors. Among those, i) estimation of charge-ordering patterns by use of reflection spectra (θ-ET_2MM' (SCN)_4 ; MM'=RbCo, RbZn, CsZn), ii) findings of giant negative magnetoresistance in phtalocyanine compounds, iii) studies on the mid-infrared band in one-dimensional (Me_2DCNQI)_2Li_<l-x>Cu_x salts, are notable.