Magnetic properties of high entropy compound Ca0.25Sr0.5La0.25Mn0.5Ti0.5O3

Abstract

This work presents the first comprehensive study of the magnetic properties of the novel perovskite-type high-entropy oxide Ca_0.25Sr_0.5La_0.25Mn_0.5Ti_0.5O₃. A polycrystalline powder of the compound was synthesized using the solid-state reaction method. The compound crystallizes in the tetragonal system with space group I4/mcm and lattice parameters a = b = 5.48320 Å, c = 7.74480 Å, and α = β = γ = 90°. The homogeneity and uniform distribution of the constituent elements were confirmed by X-ray fluorescence analysis. The emergence of magnetic ordering at ≈ 40 K is evidenced by a maximum in the temperature-dependent ESR integrated intensity, coinciding with the divergence of the ZFC/FC magnetization curves. The ESR spectrum itself is well fitted by four lines. A second, distinct phase transition is observed at approximately 300 K. Magnetization hysteresis loops measured below room temperature exhibit weak ferromagnetic behavior, with the coercive field increasing to 750 Oe at 5 K. The sign reversal of the Seebeck coefficient at T ≈ 475 K indicates a change in the conductivity type of the compound. The temperature dependence of the sample's conductivity was described within the small polariton hopping model, and the activation energy was 269 meV.