An active field of research of our group is that related to the double perovskites of general formula A2(BB’)O6, where A stands for an alkali-earth metal and B, B’ are transition metals of the first and second (or third) rows. The most representative example is Sr2FeMoO6, ferrimagnetic and half-metallic, which is considered, at present, among the most promising MR materials, given their high TC and MR at low field.
Recently, we demonstrated that high pressure is a powerful tool to minimize the unwanted antisite Fe/Mo disordering: degrees of ordering close to 100% can be obtained by pressure treatments starting from partially disordered perovskites (70% order). Additionally, we have prepared, also under pressure, the perovskite Sr2FeReO6 and, adequately tuning the oxidizing/reducing conditions, a large number of novel oxides like Sr2BUO6 (B= Mn, Fe, Ni, Zn), A2CrSbO6 (A= Ca, Sr), Ba2BSbO6 (B= Fe, Co), Sr2MReO6 (M= Ni, Co, Zn), etc…
Besides the currently exploited ideas to improve the properties of interest, based upon cationic substitutions, we aim to develop more original ideas based upon changing the anionic sublattice, enhancing the covalence of the chemical bonds, through nitridation or flourination of the previously formed oxide, thus favouring the first-neighbour magnetic interactions and enhancing ferromagnetism.
High-pressure synthesis of the double perovskite Sr2FeMoO6: increment of the cationic ordering and enhanced magnetic properties . Retuerto, M.; Martinez-Lope, M. J.; Garcia-Hernandez, M.; Alonso, J. A. JOURNAL OF PHYSICS-CONDENSED MATTER 21, 186003 (2009)
A Structural and Magnetic Study of the Series of Double Perovskites Ca2Fe1+xW1-xO6, Retuerto, M, Alonso, JA, Martinez-Lope, MJ, Garcia-Hernandez, M, Lopez, CA, Viola, MD, Pedregosa, JC, Fernandez-Diaz, MT, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 25, 3750- 3757 (2009)
Study of the valence state and electronic structure in Sr2FeMO6 (M = W, Mo, Re and Sb) double perovskites, Retuerto, M, Jimenez-Villacorta, F, Martinez-Lope, MJ, Huttel, Y, Roman, E, Fernandez-Diaz, MT, Alonso, JA, PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12, 13616-13625 (2010).
Raman and infrared spectroscopy of Sr2B’UO6 (B ‘ = Ni; Co) double perovskites, Moreira, A. F. L.; Garcia-Flores, A. F.; Granado, E.; Massa, N. E.; Pinacca, R. M.; Pedregosa, J. C.; Carbonio, R. E.; Munoz, A.; Martinez-Lope, M. J.; Alonso, J. A.; del Campo, L.; Meneses, D. De Sousa; Echegut, P.,VIBRATIONAL SPECTROSCOPY 54, 142-147 (2010)
Enhancing Magnetic and Magnetotransport Properties by Topotactic Reduction of the Sr2Fe1.33Mo0.66O6 Double Perovskite, Lopez, CA, Viola, MD, Pedregosa, JC, Alonso, JA, Fernandez-Diaz, MT, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 26, 4110- 4120 (2010)
Crystallo-chemical evolution of the La2ZnTiO6 double perovskite upon reduction: A structural study, Aguadero, A.; Alonso, J. A.; Martinez-Lope, M. J.; Fernandez-Diaz, M. T., SOLID STATE SCIENCES 13, 13-18 (2011)