Structure and Magnetic Properties of KRuO₄

Abstract

The crystal structure of KRuO is refined at both 280 and 3.5 K from neutron powder data, and magnetic properties are reported for the first time. The scheelite structure, I4/a, is confirmed at both temperatures. Atomic positions of greater accuracy than the original 1954 X-ray study are reported. The rare Ru ion resides in a site of distorted tetrahedral symmetry with nominal electronic configuration 4d(e). Curie-Weiss parameters are near free ion values for the effective moment and θ = -77 K, indicating dominant antiferromagnetic (AF) correlations. A broad susceptibility maximum occurs near 34 K, but long-range AF order sets in only below 22.4 K as determined by magnetization and heat capacity data. The entropy loss below 50 K is only 44% of the expected R ln 2, indicating the presence of short-range spin correlations over a wide temperature range. The Ru sublattice consists of centered, corner-sharing tetrahedra which can lead to geometric frustration if both the nearest-neighbor, J, and the next-nearest-neighbor, J, exchange constants are AF and of similar magnitude. A spin dimer analysis finds J/J ≈ 25, indicating weak frustration, and a (d) ground state. A single, weak magnetic reflection was indexed as (110). The absence of the (002) magnetic reflection places the Ru moments parallel to the c axis. The Ru moment is estimated to be 0.57(7) μ, reduced from an expected value near 1 μ. A recent computational study of isostructural, isoelectronic KOsO predicts a surprisingly large orbital moment due to spin-orbit coupling (SOC). However, the free ion SOC constant for Ru is only ∼30% that of Os, so it is unclear that this effect can be implicated in the low ordered moment for KRuO. The origin of the short-range spin correlations is also not understood.

Magnetic and Structural Studies of G-Phase Compound Mn6Ni16Si7

“…To obtain the magnetic contribution to the heat capacity of Mn 6 Ni 16 Si 7 one needs to subtract that of a suitable lattice match, normally a paramagnetic iso-structural compound. 38 A previous study of the magnetic properties of Ti 6 Ni 16 Si 7 showed a Pauli paramagnetic like behaviour, 25 which was also observed in our measurements of magnetic susceptibility of the compound under an applied magnetic field of 1000 Oe (SI-3).…”

Synthesis and Electrochemical Activity of Some Na(Li)‐Rich Ruthenium Oxides with the Feasibility to Stabilize Ru6+

“…We found this new phase to be isostructural to KRuO 4 , as determined from Rietveld refinements (Figure d), hence called hereafter Td‐NaRuO 4 . It crystallizes in I 4 1 / a space group, with however smaller cell parameters ( a = 5.24501(3) Å, c = 12.11654(13) Å for NaRuO 4 compared to KRuO 4 ( a = 5.6105(5) Å, c = 12.959(1) Å) . Akin in KRuO 4 , Ru, and Na are in tetrahedral and sevenfold coordination, (Figure e; Table S9, Supporting Information).…”

“…We have reported the synthesis of two new phases, namely, Li 2 RuO 4 and Td-NaRuO 4 which is isostructural to KRuO [21,23] From the compilation of the aforementioned Li(Na)(K) x RuO 4 phase diagrams, a trend seems to emerge; the smaller is the alkali, i) the higher is the coordination of Ru and ii) the lower is the oxidation state of Ru.…”

“…It crystallizes in I 4 1 /a space group, with however smaller cell parameters (a = 5.24501(3) Å, c = 12.11654(13) Å for NaRuO 4 compared to KRuO 4 (a = 5.6105(5) Å, c = 12.959(1) Å). [21] Akin in KRuO 4 , Ru, and Na are in tetrahedral and sevenfold coordination, (Figure 7e; Table S9, Supporting Information). Interestingly, we could never isolate Td-NaRuO 4 , and the highest fraction of Td-NaRuO 4 over CER-Na 2 RuO 4 was found to be 30(3)% after the removal of 1 Na from CER-Na 2 RuO 4 .…”

Emergent odd-parity multipoles and magnetoelectric effects on a diamond structure: Implication for the 5d transition metal oxides AOsO4(A=Hayami1, Kusunose2, Motome3 2018Phys. Rev. B410120View full textAdd to dashboardCite

“…There are other candidate materials with the diamond structure that possess such odd-parity multipoles. For example, KRuO 4 , whose crystal structure is similar to AOsO 4 , shows a staggered magnetic order along the z direction 48,49 , which implies the emergence of magnetic quadrupoles. Spinels AB 2 O 4 are another candidates, as the A sites comprise the diamond structure.…”