Perovskites with general formula A2B‘B‘‘O6 (where A= La; Pr; Sr; Ba and etc.; B‘ and B‘‘ = W; Co; Mn; Fe; Mo and etc.) and their solid solutions attract attention because of possibility to create half-metallic ferromagnets that was first introduced by de Groot et al. [1]. The influence of spin effect in these materials depends from degree of polarization and density of states at Fermi level which depends from both the valence state and the average size of B‘ and B‘‘ cations. Exactly the density of state at the Fermi level defines the existance of spin up or spin down channel that have metallic behavior or insulator behavior. Also these materials have unique physical properties: high Fig.1. Diffraction patterns of perovskite measured at the HRFD and treated with Rietveld method. spin polarization of electron conducting and high tunnel magnetoresistance effect in low magnetic fields at room temperatures [2, 3] and high values of the Curie temperature. All this physical properties are useful for practical using in spin devices (spintronic) for creating of spin valve and magnetic fields detectors. The main aim of the work is definition of temperature influence and substitution of barium by strontium ions to structural features and magnetic properties of double perovskites: Sr2-xBaxFeMoO6 (x = 2; 0.5; 1). All samples were prepared by solid state method at temperature 12000С in a continuous stream H2/Ar during 10 h. The crystal and magnetic structures were investigated at the High Resolution Fourier Diffractometer HRFD) [4] at the IBR-2 pulsed nuclear reactor in Dubna in a wide temperature range (20 – 300 K). The Curie temperature was defined by ponderomotive method. According to neutron diffraction all investigated samples are homogeneous. The substitution of Ba by Sr ions leads to changes of crystal structure: cubic (Fm-3m)→ orthorhombic (Fmmm)→ tetragonal (I4/m). The volume of unit cell (see Fig.1) and the Curie temperature decreases as the concentration of strontium ions are increased.