Magnetic and other studies of ruthenium dioxide and its hydrate

Abstract

The magnetic behaviour of ruthenium dioxide up to 1000°K is interpreted in terms of J being ca. -3000 cm.-l in dioxo-bridged chains of ruthenium atoms. The high electrical conductivity as well as certain structural features imply that the average oxidation state of the ruthenium atoms is substantially greater than +4.The oxide hydrate has a high surface area ; it is formulated as Ru02+,, yH,O since there can be an excess (chemisorbed) of oxygen particularly after removal of some of the water. Values of x up to 0.1 2 have been found whereas y is often 1 to 1.3. The susceptibility, though generally similar to that of RuO,, varies from sample to sample: its behaviour is discussed in relation both to the influence of adsorbed groups and also to some terminal ruthenium atoms behaving as mononuclear Ru(V), i.e., being in the d3 state. Expected spectral bands in the infrared have not been detected owing to the presence of electronic conductance bands. Solid State Physics Divisions, A.E.R.E., Harwell. Berkshire IN a recent note,l Cotton and Mague conclude that ruthenium dioxide has the rutile structure ; however, they point out that the closest Ru-Ru distance (3.107 A) excludes metal-metal coupling as the cause of the very of this second term and certain other properties to strong super-exchange, via the dioxo-bridges, in the chains (A) which exist in the c direction. Strong bondlow magnetic susceptibility. In this paper we report \RU/O\ /OARL,/ magnetic susceptibility measurements from 1.3 to from 298-673"~ together with other properties of the / \o/Ru\o/ \ 1033"~, supplementing previously available values (A) dioxide. The susceptibility per g.-atom of ruthenium, defined as XA-Xdia, has a temperature independent term ( N a ) which is relatively large, about 185 x lo* e.m.u. ; the temperature dependent term is small, about 20 x e.m.u. at room temperature and about 85x lo4 e.m.u. at 1000"~. We attribute the smallness ing within the chains is also indicated by the contraction along the c axis with increase of temperature that we have observed.The shape of the susceptibility-temperature curve is completely different from that predicted3 for a mononuclear 4d4 svstem in an octahedral environment but 1 F.

Itinerant Antiferromagnetism in RuO2

“…2(d). The value of 1.7 × 10 −4 emu/mol (300 K) is in good agreement with previous reports [8,17,18]. The 30% rise of the magnetic susceptibility with increased temperature from 300 K to 1000 K is also in excellent agreement with Fletcher et al [18], the only study that measured up to 1000 K. Our measurements, however, either produce a clear, broad maximum in the susceptibility or a significant leveling at the highest temperature, consistent with the presence of short-range ordering.…”

“…The value of 1.7 × 10 −4 emu/mol (300 K) is in good agreement with previous reports [8,17,18]. The 30% rise of the magnetic susceptibility with increased temperature from 300 K to 1000 K is also in excellent agreement with Fletcher et al [18], the only study that measured up to 1000 K. Our measurements, however, either produce a clear, broad maximum in the susceptibility or a significant leveling at the highest temperature, consistent with the presence of short-range ordering. Due to the extreme difficulty in measuring small magnetic signals at such high temperature, which is near the limit of our instrument capability, as well as the possible loss of oxygen, different crystals produce slightly different behavior above 850 K. It is possible that this changing magnetic behavior above 900 K is related to the vanishing of the (100) peak and its underlying magnetic and/or structural order.…”

“…This general belief probably stems from the early work by Ryden et al [8] that concluded Pauli paramagnetism from the quadratic temperature dependence of the magnetic susceptibility within 4-300 K. However, older measurements of the magnetic susceptibility [17,18] were performed for much larger temperature ranges up to 1000 K and demonstrated instead a linear increase as a function of temperature. We repeated those measurements while ramping the temperature continuously from 4 K to 300 K and from 300 K to 1000 K. The results are presented in Fig.…”

Correlation of the Charge Storage and Magnetic Susceptibility of Hydrous RuO2

“…As shown in Fig 3a, the Curie-Weiss parameter decreases as the samples are heated at higher temperatures, supporting previous indications that that electron delocalization or metallicity increases with decreasing water in the structure [3]. The TIP confirms that portions of the materials are metallic, or have delocalized electrons.…”

Instability of Amorphous Ru‐Si‐O Thin Films under Thermal Oxidation

“…A main absorption maximum at 310 nm for RuO 4 (oxidation state d 0 ) 17 has been published by Wells et al, 18 while the reflectance spectrum for RuO 2 (oxidation state d 4 ) 17 is reported to exhibit a broad band from 430 to 700 nm, centered at 585 nm. 19 Accounting for the width of the peak and the resolution of the spectrometer, our result clearly proves the presence of RuO 4 on the walls of the test-tube and thus the loss of ruthenium from the film during annealing in dry oxygen at 600ЊC.…”