Spin orders and lattice distortions of geometrically frustrated 6H-perovskites Ba3B′Ru2O

Abstract

The magnetic and crystal structures of the title materials have been investigated using high-resolution neutron and synchrotron x-ray powder diffraction. Ferromagnetic Ru dimers are observed in the spin-ordered ground states of all three materials, evidencing an intradimer double exchange interaction. Antiferromagnetic order between dimers breaks the degeneracy of the triangular lattice but no distortion of the B = La and Y structures is observed. The magnetic ordering transition temperature increases with the radius of the B cation. An anomalous 120 K structural transition in Ba 3 NdRu 2 O 9 is attributed to Jahn-Teller distortion, evidenced by large-amplitude 6 deformations of the NdO 6 octahedra. Further lattice anomalies accompany magnetic ordering transitions at 24 and 18 K in Ba 3 NdRu 2 O 9 . Nd spins order ferromagnetically and a substantial magnetic anisotropy leads to large coercivity and 1 3 -magnetization steps in the magnetic hysteresis loop.

Frustrated spin- 12 molecular magnetism in the mixed-valence antiferromagnets Ba3MRu2O9Ziat1, Aczel2, Sinclair3 et al. 2017Phys. Rev. B314303View full textAdd to dashboardCite

“…3(b). This also explains the much larger magnetic moment observed in neutron diffraction experiments [18]. It is natural to ask what structural parameter gives rise to this dramatic difference between the La sample and the In, Y, and Lu analogs studied here.…”

“…We note that our O 2 z parameter for the Y system is significantly different from the value reported in Ref. [18]. Upon careful inspection their value appears to be somewhat unphysical [20] IV.…”

“…Even if that were possible, the model would imply S = 5/2 dimers in the La compound which would lead to much larger values of susceptibility than are measured. Furthermore, subsequent neutron diffraction measurements of the Y system found no evidence for the required charge ordering within the dimers down to 2 K [18]. For these reasons, the magnetic ground state of the Ru dimers has also been discussed more recently in the context of molecular double exchange [18], but this simple model cannot explain the non-monotonic T -dependence of the magnetic susceptibility, the low-T entropy release in the specific heat data, and the small ordered moment sizes for the Y and La systems found in neutron diffraction.…”

Electronic structure and spin-orbit driven magnetism ind4.5insulatorBa3YIr2O9

“…Calculations revealed an environment of Ir-Ir dimer to be unaffected ruling out the possibility of a CO state very similar to Ba 3 M 3+ Ru 2 O 9 systems [37].…”

Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

“…Sharp steps in magnetic hysteresis below 8 K are observed in this compound which can be related to the antisite disorder. Field-induced steps in magnetization have been observed in several classes of materials like the geometrically frustrated magnets, 18 magnetic cluster materials, 19 spin chain compounds, 20 intermetallics, 21,22 and in manganites. 23 In the case of intermetallics, as the applied magnetic field is varied the elastic strain at the domain boundaries acts against the antiferromagnetic-ferromagnetic transformation and leads to the steps in magnetization.…”