In present investigation exchange interactions of Pr<sub>n+1</sub>Co<sub>3n+5</sub>B<sub>2n</sub>-type compounds have been evalu-ated in the light of molecular-
The procedure of preparing specimens of ultrafine particles (UFP) Fe<sub>3</sub>O<sub>4</sub> was studied and themeasurement and analysis of the Mssbauer spectra