title: Structure and Magnetic Properties of KRuO4.
abstract: The crystal structure of KRuO4is refined at both 280 and 3.5 K from neutron powder data, and magnetic properties are reported for the first time. The scheelite structure, I41/a, is confirmed at both temperatures. Atomic positions of greater accuracy than the original 1954 X-ray study are reported. The rare Ru7+ion resides in a site of distorted tetrahedral symmetry with nominal electronic configuration 4d1(e1). 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, J1, and the next-nearest-neighbor, J2, exchange constants are AF and of similar magnitude. A spin dimer analysis finds J1/J2≈ 25, indicating weak frustration, and a (dz2)1ground 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 Ru7+moment is estimated to be 0.57(7) μB, reduced from an expected value near 1 μB. A recent computational study of isostructural, isoelectronic KOsO4predicts a surprisingly large orbital moment due to spin-orbit coupling (SOC). However, the free ion SOC constant for Ru7+is only ∼30% that of Os7+, so it is unclear that this effect can be implicated in the low ordered moment for KRuO4. The origin of the short-range spin correlations is also not understood.
authors.forename: Casey A
authors.initials: CA
authors.lastname: Marjerrison
authors.affiliation: Department of Chemistry, University of Winnipeg , Winnipeg, Manitoba R3B 2E9, Canada.
authors.forename: Cole
authors.initials: C
authors.lastname: Mauws
authors.affiliation: Department of Chemistry, University of Winnipeg , Winnipeg, Manitoba R3B 2E9, Canada.
authors.forename: Arzoo Z
authors.initials: AZ
authors.lastname: Sharma
authors.affiliation: Department of Chemistry, University of Winnipeg , Winnipeg, Manitoba R3B 2E9, Canada.|Canadian Institute for Advanced Research , Toronto, Ontario M5G 1Z8, Canada.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Wiebe
authors.affiliation: Department of Chemistry and Biochemistry, California State University at Long Beach , Long Beach, California 90840-9507, United States.
authors.forename: Shahab
authors.initials: S
authors.lastname: Derakhshan
authors.affiliation: Canadian Neutron Beam Centre, Canadian Nuclear Laboratories , Chalk River, Ontario K0J 1J0, Canada.
authors.forename: Chad
authors.initials: C
authors.lastname: Boyer
authors.affiliation: Canadian Institute for Advanced Research , Toronto, Ontario M5G 1Z8, Canada.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gaulin
authors.forename: John E
authors.identifier: http://orcid.org/0000-0003-1307-8379
authors.initials: JE
authors.lastname: Greedan