STUDY OF THE TEMPERATURE DEPENDENCES OF HEAT CAPACITY OF SOLID SOLUTIONS BASED ON HEXAGONAL STRONTIUM FERRITES SUBSTITUTED WITH GALLIUM

Zhivulina N.A.⁽¹⁾, Zhivulin V.E.⁽¹⁾, Vinnik D.A.^(1,2,3)

⁽¹⁾ South Ural State University

454080, Chelyabinsk, Lenina pr., 76

⁽²⁾ Moscow Institute of Physics and Technology

1173031, Moscow, Kerchenskaya st., 1A

⁽³⁾ St. Petersburg State University

199034, Saint Petersburg, Universitetskaya emb., 7–9

Synthesis of samples of the composition SrFe₁₂₋ₓGaₓO₁₉ was carried out using the solid-phase reaction method, with iron oxide (Fe₂O₃), gallium oxide (Ga₂O₃), and strontium carbonate (SrCO₃) as starting components. Sintering of the stoichiometric mixture was performed at a temperature of 1400 °C for 5 hours. X-ray phase analysis showed that the samples have a single crystalline phase belonging to the magnetoplumbite structure. Electron microscopy and EDS analysis confirmed the homogeneous distribution of elements throughout the sample volume.

Temperature dependences of heat capacity

Measurements of the temperature dependence of heat capacity (Cₚ) were carried out using a Netzsch differential scanning calorimeter, model STA 449 C. The heat capacity was calculated by comparison with a standard (single-crystal Al₂O₃). From Figure 1, it can be seen that for the SrFe₁₂O₁₉ sample, two thermal effects are observed. The exothermic effect is associated with the ferrimagnet–paramagnet transition (denoted as Tс). For the SrFe₉Ga₃O₁₉ and SrFe₆Ga₆O₁₉ samples, no thermal effect associated with the magnetic phase transition is observed; however, these samples are ferrimagnets and have Curie temperatures above room temperature (indicated by arrows in Figure). The nature of the second thermal effect (endothermic), observed for all samples except SrGa₁₂O₁₉, is unknown. It has been suggested that it is related to the redistribution of Fe³⁺ cations over crystallographic positions.

The study was carried out with financial support from the Ministry of Education and Science of the Chelyabinsk Region through a grant in the form of a subsidy № 184/3 dated December 25, 2024, for the establishment of a regional youth laboratory.