Physical properties of fluorides barium and calcium nanopowders produced by the pulsed electron beam evaporation method

The mesoporous nanocrystal powders BaF2 and CaF2 with a specific surface up to 34.8 and 88.7 sq.m/g, respectively, are produced by the pulsed electron beam evaporation method in vacuum. The influence of thermal annealing of nanoparticles on air in the range of temperature from 200 to 900°C on the size, morphology of particles and change of their magnetic and luminescent properties investigated have been investigared. The essential stoichiometric impurity (overage of metals) and significant growth in a specific surface of nanopowders (NP) BaF2 and CaF2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF2. Produced NP CaF2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF2. Appearance of the ferromagnetic response can be explained with formation of structural and radiation defects (F-centers, etc.). The analysis of PCL and magnetization curves of samples BaF2 and CaF2 allows drawing conclusions about their connection.