title: Complex magnetic behaviour of Sr2CoNb1-xTixO6 (0 ≤ x ≤ 0.5) as a result of a flexible microstructure.
abstract: We report the rich magnetic behaviour of Sr2CoNb1-xTixO6 (0 ≤ x ≤ 0.5) oxides as a result of their complex microstructure. Although these oxides show an average simple-cubic perovskite structure, they present a flexible microstructure due to short-range ordering between Co/Ti and Nb cations in the perovskite B-sites. The microstructure consists of double-cubic perovskite domains grown in a simple-cubic perovskite matrix. The size and number of the double-cubic perovskite domains decrease as the Ti content increases. As a result of aliovalent substitution of Nb(5+) by Ti(4+) in the parent Sr2CoNbO6 mixed-valence Co(3+)/Co(4+) oxides are obtained. A spin glass-like state has been observed at low temperatures for all the series, with freezing temperatures increasing with the Ti-content in the range 22 to 33 K. Furthermore, the x = 0.3 and x = 0.5 samples show non-interacting superparamagnetic particle-like dynamics associated with relatively high amounts of Co(4+), with "blocking temperatures" of 13 and ∼16 K, respectively. The complex magnetic behaviour of the title oxides seems to be connected with the clustering of magnetic Co(3+) and the distribution of Co(4+) as a result of the microstructure.
authors.affiliation: Departamento de Química, Facultad de Farmacia, Universidad CEU San Pablo, Urb. Montepríncipe, Boadilla del Monte, E-28668, Madrid, Spain. azcondo@ceu.es.
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Azcondo
authors.forename: Julio
authors.initials: J
authors.lastname: Romero de Paz
authors.forename: Khalid
authors.initials: K
authors.lastname: Boulahya
authors.forename: Clemens
authors.initials: C
authors.lastname: Ritter
authors.forename: Flaviano
authors.initials: F
authors.lastname: García-Alvarado
authors.forename: Ulises
authors.initials: U
authors.lastname: Amador