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

The mesoporous nanocrystal powders BaF 2 and CaF 2 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) BaF 2 and CaF 2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF 2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF 2 . Produced NP CaF 2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF 2 . 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 BaF 2 and CaF 2 allows drawing conclusions about their connection. © Published under licence by IOP Publishing Ltd.The authors are grateful to Pryanichnikov S.V., a researcher of the shared equipment center “Ural” of the Institute of Metallurgy of the Ural division of RAS, for the X-ray phase analysis; to the researchers of the Institute of Electrophysics of the Ural division of RAS Demina T.M. for the texture analysis, Murzakayev A.M. and Timashenkova O.R. for the microscopic analysis, Spirina A.V. for the PCL analysis. This work has been carried out within the scope of government order No. 0389-2015-0026 and with partial support of RFBR project No. 18-08-00514. The magnetic measurements were carried out within the scope of government order under the topic MAGNIT, state registration No. AAAA-A18-118020290129-5