Schottky specific heat of the lightly Mn-substituted electron-doped SrTiO3

Large changes in the low-temperature specific heat (low-T C) by applying magnetic fields up to 9 Tesla were found in the lightly Mn-substituted electron-doped perovskites Sr1−xLaxTiO3. The changes in the low-T C are qualitatively well explained by the Schottky specific heat (CSch) of localized spins of the Mn 3d electrons in weak internal magnetic fields via itinerant electrons. According to the analysis by using the conventional model, the doped Mn ions are apparently not Mn4+ (S = 3/2) ions, but are Jahn-Teller active Mn3+ (S = 2) ions or mixtures of Mn3+ and Mn2+ ions. However, the actual numbers of localized spins estimated from CSch are about 30% smaller than the expected values. Part of the localized spins of the Mn 3d electrons may disappear due to Kondo coupling with the itinerant electrons, leading to the observed enhancement of the electronic specific heat coefficients.