Ferromagnetic intermolecular interactions in a series of organic mixed crystals of galvinoxyl radical and its precursory closed shell compound

摘要

The magnetic properties of the 4:1, 6:1, 9:1, and 19:1 mixed crystals of galvinoxyl (4hyphen;lsqb;lsqb;3,5hyphen;bis(1,1hyphen;dimethylethyl)hyphen;4hyphen;oxohyphen;2,5hyphen;cyclohexadienhyphen;1hyphen;ylidenersqb;methylrsqb;hyphen;2,6 hyphen;bis(1,1hyphen;dimethylethyl) phenoxy) radical and its precursory closed shell compound, hydrogalvinoxyl, have been studied. From the measurements of the temperature dependence of the magnetic susceptibility, it is found that the ferromagnetic intermolecular interactions, which are lost below about 85 K in pure galvinoxyl because of the phase transition, are maintained down to 2 K in these mixed crystals, and that the number of galvinoxyl radicals keeping the ferromagnetically coupled structure at low temperature increases as the concentration of hydrogalvinoxyl increases. The magnetic behavior of the mixed crystals at low temperature depends on the thermal history of the sample and is well interpreted by assuming the presence of a glassy state into which the highhyphen;temperature, ferromagnetically coupled phase is quenched. The magnetization curves show the spin multiplicity to be almost in proportion to the radical concentration in the mixed crystal and may be qualitatively understood by assuming that the mixed crystal is an assembly of onehyphen;dimensional chain segments partitioned by hydrogalvinoxyl within which the galvinoxyl radicals are coupled ferromagnetically.