Crystal structure and the magnetic properties of the 5d transition metal oxide AOsO4 (A = K, Rb, Cs)

Abstract

We synthesized the 5d1-transition metal oxides AOsO4 (A = K, Rb, Cs) by solid-state reaction, and performed structure determination and magnetic and heat capacity measurements. It was found that they crystallize in a scheelite (A = K and Rb) or a quasi-scheelite structure (A = Cs) comprising of distorted diamond lattices of septivalent Os (d1) ions tetrahedrally coordinated by four oxide ions without local inversion symmetry; hence an antisymmetric spin-orbit coupling is expected in the crystals. The K and Rb compounds have Weiss temperatures of theta = -66 and -18 K, effective magnetic moments of mu_eff = 1.44 and 1.45 mu_B/Os, and antiferromagnetic transition temperatures of T_N = 36.9 and 21.0 K, respectively. In contrast, the Cs compound has theta = 12 K and mu_eff = 0.8 mu_B/Os without magnetic transition above 2 K, instead exhibiting a first-order structural transition at T_s = 152.5 K. The decline of the Os moment from 1.73 mu_B/Os for the simple d1 spin, particularly for Cs, is likely to originate from the antiparallel orbital moment, although the spin-orbit coupling is generally quenched in the low-lying e orbitals.

21 pages, 7 figures

References in corpus (9)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Ferromagnetism in the Mott insulator Ba2NaOsO6
• Tetrahedral Magnetic Order and the Metal-Insulator Transition in the Pyrochlore Lattice of Cd2Os2O7
• Cooperative Effect of Electron Correlation and Spin-Orbit Coupling on the Electronic and Magnetic Properties of Ba2NaOsO6
• Pyrochlore Oxide Superconductor Cd2Re2O7 Revisited
• Orbital-quenching-induced magnetism in Ba_2NaOsO_6
• Emergent odd-parity multipoles and magnetoelectric effects on a diamond structure: implication to 5$d$ transition metal oxides $A$OsO${}_4$ ($A=$ K, Rb, and Cs)
• Successive spatial symmetry breaking under high pressure in the spin-orbit-coupled metal Cd2Re2O7
• Unquenched $e_g^1$ orbital moment in the Mott insulating antiferromagnet KOsO4

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