ABSTRACT
The Ca2MnReO6double perovskite is a spin-orbit-assisted Mott insulator with exotic magnetic properties, including a largely non-collinear Mn2+spin arrangement and nearly orthogonal coupling between such spins and the much smaller Re 5dmagnetic moments. Here, the electron-doped compound Ca1-xYxMnReO6(x= 0.1, 0.2 and 0.3) is reported and a detailed investigation is conducted forx= 0.3. Neutron and x-ray powder diffraction confirm that nearly full chemical order is maintained at the Mn and Re sites under the Y substitution at the Ca site. X-ray absorption measurements and an analysis of the Mn-O/Re-O bond distances show that the Mn oxidation state remains stable at +2 whereas Re is reduced upon doping. The electron doping increases the magnetic ordering temperature fromTc= 121 to 150 K and also enhances significantly the ferromagnetic component of the Mn spins at the expense of the antiferromagnetic component at the base temperature (T= 3 K). The lattice parameter anomalies atTcobserved in the parent compound are suppressed by the electron doping. The possible reasons for the enhanced magnetism and the suppressed magnetoelastic coupling in Ca1.7Y0.3MnReO6are discussed.
ABSTRACT
We report the electronic and magnetic properties of stoichiometric CeAuBi2 single crystals. At ambient pressure, CeAuBi2 orders antiferromagnetically below a Néel temperature (TN ) of 19 K. Neutron diffraction experiments revealed an antiferromagnetic propagation vector τ ^ = [ 0 , 0 , 1 ∕ 2 ] , which doubles the paramagnetic unit cell along the c axis. At low temperatures several metamagnetic transitions are induced by the application of fields parallel to the c axis, suggesting that the magnetic structure of CeAuBi2 changes as a function of field. At low temperatures, a linear positive magnetoresistance may indicate the presence of band crossings near the Fermi level. Finally, the application of external pressure favors the antiferromagnetic state, indicating that the 4f electrons become more localized.