Soft ferromagnetism in mixed valence Sr1−xLaxTi0.5Mn0.5O3 perovskites

Abstract

The structural, magnetic and electrical properties of the mixed Ti–Mn oxides Sr_1−xLa_xTi_0.5Mn_0.5O₃ (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 Sr_0.6La_0.4Ti_0.5Mn_0.5O₃ 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 (Mn^3+/4+) examples is dominated by ferromagnetic interactions, although cation disorder frustrates long range magnetic ordering.