The crystallographic and magnetic structures of Ca 3 Mn 2 O 7 Ruddlesden-Popper phase have been determined by a combination of neutron and synchrotron x-ray diffraction. Two-phase behaviour observed at room temperature is attributed to an incomplete structural phase transition. The magnetic structure was solved in the Cm c2 1 Shubnikov group with dominant G-type antiferromagnetic order in the perovskite bilayers. The temperature evolution of the structural and magnetic parameters is presented.

The magnetic susceptibility, crystal and magnetic structures, and electronic structure of double perovskite Sr2ScOsO6 are reported. Using both neutron and x-ray powder diffraction we find that the crystal structure is monoclinic P21/n from 3.5 to 300 K. Magnetization measurements indicate an antiferromagnetic transition at T N = 92 K, one of the highest transition temperatures of any double perovskite hosting only one magnetic ion. Type I antiferromagnetic order is determined by neutron powder diffraction, with an Os moment of only 1.6(1) µ B , close to half the spin-only value for a crystal field split 5d electron state with t2g 3 ground state. Density functional calculations show that this reduction is largely the result of strong Os-O hybridization, with spin-orbit coupling responsible for only a ∼ 0.1 µ B reduction in the moment. PACS numbers: 75.25.-j, 71.15.Mb, 71.70.Ej It is important to understand the nature of the d 3 electronic state, as it appears to produce the highest magnetic transition temperatures found in perovskite systems [1]. Perovskites NaOsO 3 , 5d 3 , and SrTcO 3 , 4d 3 , have T N = 411 K and T N ≈ 1000 K, respectively [2-5]. In the double perovskite Sr 2 CrOsO 6 two d 3 ions are present, Cr 3+ 3d 3 and Os 5+ 5d 3 , and a ferrimagnetic transition with T C = 725 K is found, the highest known transition temperature in any double perovskite [6]. However, the presence of two magnetic ions in Sr 2 CrOsO 6 makes the interactions controlling this high-T C insulator more difficult to unravel [7]. It is clear that the influence of the Os 5d 3 electrons must be understood in order to ultimately understand the high-T C found in Sr 2 CrOsO 6. The d 3 electronic configuration in a perovskite-type structure is, at first sight, an unlikely host of complex magnetic behavior. The octahedral environment splits the d orbitals into t 2g and e g levels, stabilizing a half occupied t 2g 3 configuration. This is normally assumed to be fully orbitally quenched, resulting in a relatively classical S = 3/2 moment behavior [8]. However, many investigations in 4d 3 and 5d 3 compounds have found that the ordered magnetic moment measured by neutron diffrac-tion is significantly reduced from the spin only value of µ = 3 µ B [3, 9-14]. Explanations of this reduced moment have centered on covalency and frustration. It has recently been suggested, however, that the effect of spin-orbit coupling (SOC) cannot be ignored in 4d 3 and 5d 3 systems [15]. In Ref. [15] they find that the electronic state may lie between L-S and J-J coupling regimes, and therefore the t 2g 3 assumption is invalid. Recent experimental investigations have therefore discussed the role of SOC in 4d 3 and 5d 3 double perovskites [9, 16-19]. Here we investigate the magnetic insulator Sr 2 ScOsO 6 , which has one of the highest known magnetic transition temperatures in double perovskites hosting only one magnetic ion [20, 21]. It is the 3d 0 −5d 3 analogue of 3d 3 −5d 3 Sr 2 CrOsO 6 , and thus serves as a model system to unravel the behavior of d 3 Os 5+....

Solid solutions of Tb(1-x)Y(x)Co(3)B(2) (x=0.05, 0.1, 0.25, 0.4 and 0.5) were studied by neutron powder diffraction, x-ray diffraction, AC susceptibility and SQUID magnetization measurements. Their magnetic and crystallographic properties were deduced and examined together with those previously published for the end compounds (x=0, 1). These solid solutions have hexagonal symmetry and are paramagnetic at RT, and undergo a magnetic ordering transition of the Co sublattice, with the magnetic moments along the hexagonal axis, at T(Co)∼150(15) K, independent of Y concentration. A second magnetic ordering transition of the Tb sublattice T(Tb)≤30 K accompanied by the rotation of the magnetic moments towards the basal plane, was observed for solid solutions with Y concentration x≤0.25. This transition was also found to be accompanied by a crystallographic symmetry decrease. Unexpectedly, neutron powder diffraction showed that the magnitude of the ordered magnetic moment of the Tb ion decreases with Tb concentration.