Crystal structure, magnetic properties and conductivity mechanisms of La_0.7Ca_0.3Mn_0.5Fe_0.5O₃

ABSTRACT

La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ (LCMFO) ceramic samples were prepared by conventional solid-state reaction. X-Ray diffraction investigations show that samples have orthorhombic space group Pnma (a = 5.447(2) Ǻ, b = 7.709(3) Ǻ, c = 5.467(3) Ǻ). During the neutron powder diffraction measurements of LCMFO in the temperature range of 10 ÷ 300 K the antiferromagnetic long-range ordering of G-type was seen. It has been established that 50% substitution of Mn/Fe leads to a complete suppression of the ferromagnetism in LCMFO samples. Investigations of temperature dependence of the magnetization, M(T), suggests the frustration of magnetic ground state and the existence of a spin-glass or a cluster-glass phase below the magnetic transition temperature close to 350 K. The temperature dependences of conductivity for La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ sample investigated in magnetic fields B = 0 and 1 T. According to the research, the mechanisms of hopping conductivity were established. Micro parameters in density of localized states were calculated for LCMFO samples. The width of the Coulomb gap Δ = 0.67 eV, rigid gap δ = 0.324 eV and the localization radii of charge carriers were estimated.

KEYWORDS:

• Manganite perovskites
• neutron diffraction
• hopping conductivity
• antiferromagnetic ordering
• ferromagnetism

Acknowledgments

This work was supported by the Ministry of Education and Science of the Russian Federation: reference number 2014/420-367. Scientific equipment of the Joint Research Centre “Diagnostics of structure and properties of nanomaterials” at the Belgorod State University was partially used to carry out this project.