Itinerant-electron ferromagnetism in W(Nb)O3−δ

Abstract

The crystal structure and the magnetic properties of the W 1-x Nb x O 3-δ , (x<0.03) system have been investigated. In contrast to the orthorhombic diamagnetic WO 3 , the material with x=0.01 is paramagnetic down to 5 K. Introducing of 2.5 at. % of Nb into WO 3 leads to a tetragonal structure and to a weak itinerant ferromagnetic ordering below T C = 225 K. The saturation magnetic moment at 5 K is 1.07*10 -3 µ B , whereas the paramagnetic effective moment is 0.06 µ B per mole. This high ratio indicates itinerant ferromagnetism in W 0.975 Nb 0.025 O 3-δ .

Electronic structure and magnetism in XxW1−xO3 (X=Nb,V,Re) from supercell calculations

“…al. 4 is tetragonal, where the concentration of Nb is lower (x ≈ 0.025) than in the supercell here, and it may have some oxygen deficiency. The goal of the present work is not to study exactly the system used in the experiment, but to find out whether the conditions for weak ferromagnetism can be found in doped oxides as was found in some hexaborides 6 , and if such conditions can be expected to be frequent around impurities in metallic compounds.…”

“…In particular, the quest of finding systems similar to the electron doped WO 3 , where small additions of Na are reported to make the system superconducting 2,3 , suggests that hole doping should work as well. Instead, doping by dilute (2.5 %) Nb substitutions on W sites leads to weak itinerant ferromagnetism 4 , with properties not too different from those of doped hexaboride systems 5 . In this work we study the electronic structure of cubic XW 26 O 81 , with X=Nb, V and Re, in order to see if similar conditions for magnetism are met as in La doped strontium hexaboride 6 .…”

Low-Dimensional Physics of Organic-Inorganic Multilayers

“…Many different layered perovskites have been used as the inorganic layers in organic-inorganic hybrids formed by chimie douce methods. These include the perovskite Ca 2 Nb 3 O 10 and its derivatives [122], the Aurivillius phases Bi 2 W n O 3n+3 [152], the MnO 2 'slab' structures birnessite and buserite [88,175], the layered double hydroxide (LDH) system, based on alumino-silicate clays [131], and even the HTS Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 superconductor series [50,52,53,80,139]. The organic molecules act primarily to separate the inorganic layers, and they may be present as neutral species or positively charged to maintain charge balance.…”