Structure and properties of nano- and polycrystalline Mn-doped CuCr2Se4 obtained by ceramic method and high-energy ball milling

Chemical compounds with a general formula CuCr2-xMnxSe4 (x = 0.1, 0.2) were successfully synthesized in polycrystalline form, using solid state reaction method, and as nanoparticles, using high-energy ball milling. The influence of manganese and grain size on their structure, magnetic and thermal properties was investigated by Xray Diffraction (XRD), Scanning Electron Microscopy (SEM), magnetic measurements (SQUID, high magnetic fields) and DSC (Differential Scanning Calorimetry). Electronic structures of obtained compounds were determined using XANES (X-ray Near Edge Absorption Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy). Xray studies confirmed that the spinel phase forms only for x = 0.1, 0.2. The obtained compounds crystallize with the space group Fd (3) over barm. The results of magnetic measurements for poly- and nanocrystalline compounds showed that the polycrystalline compounds are ferromagnets with the Curie temperature of T-C = 352 K for x = 0.1 and T-C = 342 K for x = 0.2, and the Curie-Weiss temperature of theta(CW) = 362 K for x = 0.1 and theta(CW) = 354 K for x = 0.2. Whereas the nanoparticles CuCr2-xMnxSe4 (x = 0.1, 0.2) revealed a superparamagnetic character with blocking temperature of T-B approximate to 25 K for both compounds. The XANES and XPS data indicate the Cr ions are trivalent (Cr3+). Mn ions are trivalent and tetravalent (Mn3+ and Mn4+), which implies small amount of the Cu ions change the valency from divalency to monovalency (Cu2+ and Cu1+). DSC/TG analysis indicates that the presence of Mn ions in the CuCr2Se4 crystal lattice affects the stability and resistance of the doped compounds in comparison with the pure CuCr2Se4. Decreasing the grain size leads to a decrease in melting temperature.

Automated summary

Chemical compounds CuCr2-xMnxSe4 (x = 0.1, 0.2) were successfully synthesized in polycrystalline and nanoparticle forms using solid state reaction and high-energy ball milling. The study investigated the influence of grain size and manganese content on the structure, magnetic, and thermal properties of the compounds. Results showed that decreasing grain size leads to a decrease in melting temperature, and the presence of Mn ions affects the stability and resistance of the doped compounds compared to pure CuCr2Se4.