Studies on magnetic and calorimetric properties of double perovskites Ba2HoRuO6 and Ba2HoIrO6

Giant magneto optical properties in the double perovskites Ba2B'RuO6(B' = Er, Tm)

This study aimed to investigate new double perovskite oxides in search of new promising functional material with properties of interest for high density storage applications. The crystal structure, magnetic, electronic and magneto-optical properties of the rare-earth-based double perovskites Ba₂B'RuO₆(B' = Er, Tm) were investigated through full-potential linearized augmented plane wave method within the context of density functional theory (DFT) in Wien2k code. We used generalized gradient approximation (GGA) and GGA + U approaches to calculate magneto-optical properties, including spin-orbit coupling due to 4f and 4d-electrons. The obtained DFT-optimized structures was cubic (space group: Fm = 3m), and the calculations (GGA + U) showed that the compounds Ba₂ErRuO₆is semiconductor and the Ba₂TmRuO₆is half-metal. The magneto-optical Kerr effect showed pronounced peaks at angles of 17.7^∘and 5.6^∘for an energy around 0.2 eV for both compounds, which could potentially have important applications in the infrared region or for blue and violet radiation.

Dielectric relaxation of the double perovskite oxide Ba2PrRuO6

Samples of Ba₂PrRuO₆ were prepared by the solid state reaction method and the structure was characterized by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and dielectric measurements were performed in order to investigate the morphology and electric properties of the ceramics. X-ray diffraction data reveal that the Ba₂PrRuO₆ samples are of the cubic crystal structure with the space group Fm3̄m at room temperature. The dielectric properties were studied in the range of 20 Hz to 1 MHz in the temperature range from 10 K to 300 K. Strong dispersion in frequency and a rapid increase in ε′ are observed when T > 150 K. The observed steps of the ε′(T) curves are correlated with the peaks of the tan δ(T) curves, with the peak temperature shifting to higher values as the frequency increases. Impedance spectroscopy studies indicate the presence of grain and grain boundary relaxations in the sample at high temperatures, while at low temperatures only grain relaxation can be observed. Both grain and grain boundary relaxation times follow the Arrhenius law with activation energies of 0.16 eV and 0.17 eV, respectively.

Complex plane impedance plots for Ba₂PrRuO₆ sample at different temperatures. The solid lines represent the fitting from the equivalent circuits.

Rare earth double perovskites: a fertile soil in the field of perovskite oxides

This review summarizes the compositions, syntheses, and applications of rare earth A₂B′B′′O₆ double perovskites.

Time–temperature superposition in the grain and grain boundary response regime of A2HoRuO6(A = Ba, Sr, Ca) double perovskite ceramics: a conductivity spectroscopic analysis

The realisation of a universal scaling parameter accounting for the time–temperature superposition principle in different electroactive microstructural domains seems improbable.

Magnetic and thermal responses triggered by structural changes in the double perovskite Sr2YRuO6

Among double perovskites, the interpretation of the magnetic, thermal and transport properties of Sr(2)YRuO(6) remains a challenge. Characterization using different techniques reveals a variety of features that are not understood, described as anomalous, and yields contradictory values for several relevant parameters. We solved this situation through detailed susceptibility, specific heat, thermal expansion and x-ray diffraction measurements, including a quantitative correlation of the parameters characterizing the so-called anomalies. The emergence of short-range magnetic correlations, surviving well above the long-range transition, naturally accounts for the observed unconventional behavior of this compound. High resolution x-ray powder diffraction and thermal expansion results conclusively show that the magnetic and thermal responses are driven by lattice changes, providing a comprehensive scenario in which the interplay between the spin and structural degrees of freedom plays a relevant role.