Obtaining of thin films Sr₂FeMoO_6-δ
SFMO films and multilayer structures based on the methods of ion-beam and magnetron sputtering.

Experimental parameters:

• Temperature range 2-300 K
• Magnetic field induction – up to 14 T
• Electrical current – up to 250 A
• Measurements of temperature dependences of  electrical resistance for the determination of transition temperature T_c
• Measurements of  current dependences of electrical resistance at T=78 К for a determination of j_c
• R(B) at T=78K for a determination of Вс
• Construction of the triple diagram of critical parameters T_c, j_c and B_c
• Measurements of thermophysical properties of HTSC (heat conduction λ, heat capacity c_p)
• Measurements of thermoelectric power in the temperature range 4-300 K
• Measurements of the Hall effect in magnetic fields up to 14 T

Superstructural ordering of Fe³⁺ and Mo⁵⁺ cations in Sr₂FeMoO_6-δ

The SFMO sample was synthesized from a stoichiometric mixture: (a) MoO₃, Fe₂O₃ and SrCO₃ simple oxides, and (b) SrFeO_3-х and SrMoO₄ precursors.

The use of partially reduced precursors promotes the increase of the rate of SFMO growth in the sample No. 2. The temperature of synthesis lowers as well.  Superstructural ordering of Fe³⁺ and Mo⁵⁺ cations is created. Besides, according to the XRD analysis data, additional (101) and (103) reflexes were determined.

Synthesis of Sr₂FeMoO_6-δ

The synthesis of the Sr₂FeMoO_{6-δ (} (SFMO) is carried out from the basic reagents SrCO₃, Fe₂O₃, MoO₃ in the following way:

1. mixing the initial powder reagents in a stoichiometric ratio
2. pressing of the powder
3. preliminary annealing
4. grinding
5. pressing of the powder
6. final annealing
7. obtaining a predetermined oxygen index of SFMO.

Zero-dimensional  deficiency in Sr₂FeMoO_6-δ structure

One can see from experimental results that magnetic moments of the double perovskite are lower than the theoretically calculated ones. This discrepancy can be explained by the formation of antisite point defects, such as [Fe]_Mo, [Mo]_Fe or of oxygen vacancies (V₀).

Magnetic structure of Sr₂FeMoO_6-δ

The total spin S=2 consist of spins S(Fe³⁺) = 5/2 and S(Mo⁵⁺) = -1/2. Eectronic spins Fe³⁺ and Mo⁵⁺ are placed in Fe/Mo ferrimagnetic plates, which are intercrossed at the angle 120^o. Due to the non-parallel arrangement of spins in the crystal lattice a ferrimagnetic structure is formed.