Susceptibilities of the vanadium Magnéli phasesVnO2n−1at low temperature

Abstract

The magnetic susceptibilities of the insulating Magneli phases V30~, V407, V60~~, and V80~& have been measured at low temperatures.Due to a short-range-order effect V305 exhibits a broad maximum at 125 K, which is substantially higher than the Neel temperature, 76 K, of this compound. For V407 and V60~~the difference between the Neel temperature and the temperature of the maximum in the susceptibility is small. This excludes the possibility that a linearchain model discussed by Khattak et al. can explain the specific heat of these two compounds.The temperature derivative of the susceptibility for these two compounds has a maximum at the Neel temperature which corresponds to Fisher's relation. The susceptibility for V80~5 is nearly constant between 5.6 and 68 K, and depends on past history below 5.6 K, i.e. , whether the sample is being cooled or heated. However this temperature hysteresis is sample dependent. These experimental data cannot be accounted for by an ordinary antiferromagnetic transition in the insulating state and suggest another type of transition, The possibility of the existence of a mixed charge-density and spin-density wave is discussed, since this can explain qualitatively the experimental features found for V80&5.

Synthesis, characterization, and magnetic susceptibility of the heavy-fermion transition-metal oxideLiV2O4

“…43 V 2Ϫy O 3 (yϷ0.03), on the other hand, sustains its high-T metallic state down to low temperatures, and at its Néel temperature T N ϳ10 K it undergoes a transition to an antiferromagnetic phase with a cusp in (T). 43 V 3 O 5 also orders antiferromagnetically at T N ϭ75.5 K, but (T) shows a broad maximum at a higher Tϭ125 K. 44 Though not detected in our x-ray diffraction measurements, V 4 O 7 , which has the same V oxidation state as in LiV 2 O 4 , also displays a cusp in obs (T) at T N Ϸ33 K and obs (T) follows the Curie-Weiss law for Tտ50 K. 44 The susceptibilities of these V-O phases are all on the order of 10 Ϫ4 -10 Ϫ3 cm 3 /mol at low T. 43,44 Moreover, the T variations of obs (T) in these vana-dium oxides for TՇ10 K are, upon decreasing T, decreasing (V 2Ϫy O 3 ) or nearly T independent (V 3 O 5 and V 4 O 7 ), in contrast to the increasing behavior of our Curie-like impurity susceptibilities. From the above discussion and the very small amounts of V-O impurity phases found from the Rietveld refinements of our x-ray diffraction measurements, we conclude that the V-O impurity phases cannot give rise to the observed Curie-like upturns in our obs (T) data at low T. These Curie-like terms therefore most likely arise from paramagnetic defects in the spinel phase and/or from a very small concentration of an unobserved impurity phase.…”

Vanadium Oxide Compounds: Structure, Properties, and Growth from the Gas Phase

“…Kachi et al have reported on the magnetic susceptibility, and the insulator‐to‐metal transition, in these compounds . Maximal magnetic susceptibility was observed for these compounds near the corresponding Néel temperatures . The insulator‐to‐metal transition is coupled to an anomaly in the magnetic susceptibility without long‐range magnetic order .…”

“…[96] Maximal magnetic susceptibility was observed for these compounds near the corresponding Néel temperatures. [97] The insulator-to-metal transition is coupled to an anomaly in the magnetic susceptibility without long-range magnetic order. [69,96,98] While the insulating phases are dominated by localized charges, itinerant and localized electrons coexist in the metallic phases.…”

Electronic Conduction in Oxides

“…[253,262] References [263][264][265] [244, [266][267][268][269][270][271][272][273][274][275] [276] [276][277][278] [279] [280] [ [281][282][283][284][285][286] [180] [180] [ [286][287][288][289] [281] [283,[290][291][292] x except for a peak at low [309] temp. [253,262] References [263][264][265] [244, [266][267][268][269][270][271][272][273][274][275] [276] …”