Structural Characterization and Evolution of the Electronic Behavior of New Sr2−xGdxMnTiO6 (0≤x≤1) Perovskites


  • A. Feteira—contributing editor

  • Authors acknowledge the CAI (XRD and electron microscopy) centers of UCM and financial support from Spanish Ministerio de Ciencia e Innovación, Research Projects MAT2006-10021 and MAT2010-20117 (CICYT, Spain).

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The structural and magnetic characterization of microcrystalline powders of new Ti manganites Sr2−xGdxMnTiO6 (0≤x≤ 1) are reported. Compositional characterization by means of thermogravimetric analysis, EDS, and XPS indicates the stoichiometry of all samples to be practically equal to the nominal one. A diminution in symmetry from cubic to orthorhombic has been detected as a function of x, being the critical composition x=0.75. Microstuctural aspects are deeply discussed from high-resolution transmission electron microscopy data and they confirm that for x≤0.5 a cubic symmetry is adopted, whereas for x≥0.75 the samples become orthorhombic, with space group Pbnm. The complex magnetic response of the title materials is explained considering magnetic frustration derived from the presence of two magnetic sublattices (Gd and Mn), which could interact as a function of temperature and magnetic field. The existence of antiferromagnetic interactions is especially clear for low values of x, but even in these cases, hysteresis loops in the M versus H variation are obtained at 4.2 K. The global magnetic response can be understood taking into account weak ferromagnetic (FM) interactions at the Mn sublattice (Mn4+ and Mn3+ cations) together with the greater magnetic contribution of paramagnetic Gd sublattice at low temperature. No spin reversal behavior has been detected in any case. For the most doped samples, x=0.75 and 1, a predominant FM contribution of Gd sublattice seems to be operative.