Diverse structures of mixed-metal oxides containing rare earths and their magnetic properties

Abstract

The solid state chemistry of mixed-metal oxides containing rare earths (4f elements) and 4d or 5d transition elements has attracted a great deal of interest, because these materials adopt a diverse range of structures and show a wide range of electronic properties due to 4f and 4d (or 5d) electrons. We have focused our attention on the structural chemistry and magnetic properties of perovskite-type oxides with the general formula A n LnM n¹1 O 3n (A = Ca, Sr, Ba; Ln = rare earths; M = Ru, Ir; n = 14). Their structures are controlled by changing the ratio of the Ln and M ions, and peculiar magnetic properties and magnetic structures have been investigated by magnetic susceptibility, specific heat and neutron diffraction measurements.

Hexagonal Perovskites as Quantum Materials

“…In this series, however, SrIrO3 and BaIrO3 are both monoclinic C2/c distortions of the 6H-BaTiO3 hexagonal (chc)2 structure 39,40 (former: a = 5.604 Å, b = 9.618 Å, c = 14.17 Å, beta = 93.26 o ). These structural distortions have not yet been theoretically modeled to our knowledge, but they may well be related to the influence of the strong spin orbit coupling in Ir, which is widely known to be influential in determining the magnetic and electrical properties of iridium oxide based quantum materials [41][42][43][44][45][46][47] . The monoclinic and cubic crystal structures of SrIrO3 are shown in Figure 3.…”

“…While the M ions form triangular planar lattices of potentially isolated MO6 octahedra, the M' ions form a dimer array on a triangular lattice. When either M or M' has unpaired electrons, the magnetism can make these quite interesting quantum materials due to the triangular lattice and the localized vs. delocalized character of unpaired electrons in the dimers 47 . For consistency with more complex structures, we refer to these materials simply as dimer-based hexagonal perovskites.…”

Quantum materials with strong spin–orbit coupling: challenges and opportunities for materials chemists

“…In other words, the magnetic 'units' of the structure may no longer be the individual MO 6 octahedra but multimer 'molecules'. 91,95,96…”

Magnetocaloric Effect in the Double Perovskites Sr₂RRuO₆ (R = Dy and Tb)

“…interactions between Ru magnetic moments in the ab plane are FM in Sr 2 RRuO 6 (R = Tb, Ho, Er and Tm) 12) . FM interactions have also been reported for other Ru oxides.…”