title: The effect of partial substitution of Ni by Mg on the structural, magnetic and spectroscopic properties of the double perovskite Sr2NiTeO6.
abstract: In this report, the structural, magnetic and spectroscopic properties of the freeze-drying synthesized Sr2Ni1-xMgxTeO6 (x = 0.0, 0.1, 0.2, 0.3 and 0.5) oxides are analyzed by means of X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD), electron paramagnetic resonance, diffuse reflectance and magnetic susceptibility. The XRPD and NPD data analysis using the mode-crystallography approach have revealed that at room temperature (RT), all the compositions are monoclinically distorted with the space group I2/m. The high and low temperature analyses have shown that these materials suffer a series of three structural phase transitions. The EPR results have shown that the spectra of all the compositions are centred at g≈ 2.28, indicating a slightly distorted octahedral environment of Ni(2+), which is in agreement with the crystal structure analysis. The increase of the Mg(2+) content in Sr2Ni1-xMgxTeO6, provokes a decrease of the dipolar interaction effects and thus, the resonance becomes narrower. This resonance does not completely disappear which leads to the idea that the long-range magnetic order is not completely established when x≥ 0.3. The substitution of the Ni(2+) (S = 1) ions by Mg(2+) (S = 0) ions, also induces a weakening of the antiferromagnetic interactions, which is reflected in the diminishing of the absolute value of θ and the Néel temperature TN. The magnetic structure determination revealed the existence of an antiferromagnetic coupling for x- and z-spin components of the nickel atoms.
authors.affiliation: CICenergigune, Albert Einstein 48, 01510 Miñano, Alava, Spain. borayech@cicenergigune.com orayech@gmail.com.
authors.forename: B
authors.initials: B
authors.lastname: Orayech
authors.forename: L
authors.initials: L
authors.lastname: Ortega-San-Martín
authors.forename: I
authors.initials: I
authors.lastname: Urcelay-Olabarria
authors.forename: L
authors.initials: L
authors.lastname: Lezama
authors.forename: T
authors.initials: T
authors.lastname: Rojo
authors.forename: María I
authors.initials: MI
authors.lastname: Arriortua
authors.forename: J M
authors.initials: JM
authors.lastname: Igartua