J. Phys. IV France 07 (1997) C1-371-C1-372
Electric Properties of a New Ferrite K4Cu2Fe7V7O32 with a Hollandite-Type StructureI. Jacyna-Onyszkiewicz1 and M.A. Obolensky2
1 Institute of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznah, Poland
2 Department of Physics, Kharkov State University, Svobody sq. 4, 310077 Kharkov, Ukraine
Results of investigation of electric transport properties of a new magnetically ordered hollandite compound with a composition K4Cu2Fe7V7O32 will be reported. Resistance versus temperature measurements (78-350 K) on the ceramic samples were carried out by means of four-lead dc, pulse and ac techniques. The temperature coefficient of resistance determined from R(T) measured by dc and pulse techniques has been found to be zero in 78-200 K range and it takes negative values in temperatures above 200 K. Additionally, hysteresis effect was observed in temperature range 200-310 K. Details of relationship between the resistance R and voltage U at different temperatures will be discussed. Surprisingly enough, the R(T) dependence of studied compound bears a characteristic features for amorphous material although the crystallinity of our samples has been confirmed by XRD and Mössbauer spectroscopy.
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