Charge compensation and magnetic properties in Sr and Cu doped La-Fe perovskites

Abstract

Abstract. Orthorhombic lanthanum orthoferrites La 0.8 Sr 0.2 Fe 1-y Cu y O 3-w (y = 0 and 0.10) have been studied using X-rays and neutron powder diffraction (XRPD and NPD), magnetization measurements and 57 Fe Mössbauer spectroscopy. Rietveld refinements on XRPD and NPD data show that they adopt an orthorhombic ABO 3 perovskite symmetry with La/Sr and Fe/Cu atoms randomly distributed on crystal A and B sites, respectively. The magnetic structure at room temperature is antiferromagnetic, with the Fe/Cu magnetic moments aligned along the a axis. Magnetization curves versus temperature show that the compounds exhibit an overall antiferromagnetic and a weak ferromagnetic behaviour in the range 5-298 K. 57 Fe Mössbauer spectroscopy measurements indicate that Fe 3+ and Fe 5+ ions coexist in both compounds, and the relative percentage of Fe 5+ is almost the same at 77 and 170 K, rejecting a charge disproportion mechanism.