Soft ferromagnetism in mixed valence Sr1_ xLa xTi0.5Mn0.5O3 perovskites

Abstract

The structural, magnetic and electrical properties of the mixed Ti–Mn oxides Sr1−xLaxTi0.5Mn0.5O3 (0 ≤ x ≤ 0.5) are reported. At room temperature the oxides have a cubic structure in space group Pmm for x ≤ 0.25 and rhombohedral in Rc for 0.3 ≤ x ≤ 0.50. X-ray absorption spectroscopic measurements demonstrate the addition of La3+ is compensated by the partial reduction of Mn4+ to Mn3+. Variable temperature neutron diffraction measurements show that cooling Sr0.6La0.4Ti0.5Mn0.5O3 results in a first order transition from rhombohedra to an orthorhombic structure in Imma. Complex magnetic behaviour is observed. The magnetic behaviour of the mixed valent (Mn3+/4+) examples is dominated by ferromagnetic interactions, although cation disorder frustrates long range magnetic ordering