Robert Lindsay

Weak ferromagnetism in BaIrO3

Abstract The monoclinic BaIrO 3 phase was characterized from magnetic measurements between the temperatures 78–300 K using the Faraday method. This compound was found to exhibit weak ferromagnetism with a Curie temperature of 180 ± 3 K and remanence in the magnetization below its transition temperature. A model is proposed for the weak ferromagnetism based on the canting of antiferromagnetically coupled spins.

The preparation, structure and properties of Eu2IrH5

Abstract Eu 2 IrH 5 was formed by heating EuH 2 and iridium at 700 °C in a hydrogen atmosphere. The ternary hydride is a black crystalline solid and is unreactive to ambient air. X-ray powder diffraction data were indexed as f.c.c. with a unit cell length of 7.580 A. The positions of the metal atoms conform to a fluorite lattice with the europium atoms occupying the fourfold sites and the iridium atoms the eightfold sites. The crystallinity of Eu 2 IrH 5 vanished after exposure to hydrogen at 646 atm and 250 °C. At high temperatures Eu 2 IrH 5 is paramagnetic; the susceptibility can be fitted to a Weiss-Curie law with θ = 18 K . The effective magnetic moment is 7.4 μ B which is consistent with divalent europium and monovalent iridium. Low temperature data suggest that Eu 2 IrH 5 is a ferromagnet with an ordering temperature of 20 K. The variation of the electrical resistivity with temperature is consistent with semiconductor behavior with an activation energy ΔE of 0.08 eV.

Alkylenebisdithiocarbamates of oxovanadium(IV), chromium(III), and manganese(II)

Abstract The ethylenebisdithiocarbamato and hexamethylenebisdithiocarbamato derivatives of oxovanadium(IV), chromium(III), and manganese(II) were synthesized and characterized using thermal, solubility, i.r., X-ray powder diffraction, and magnetic susceptibility measurements. Ethylenebis(dithiocarbamato)oxovanadium(IV) was a green, crystalline solid. Ethylenebisdithiocarbamatochromium(III) and hexamethylenebisdithiocarbamatochromium(III) were purple solids, insoluble in deionized water and common organic solvents. Ethylenebisdithiocarbamatomanganese(II) and hexamethylenebisdithiocarbamatomanganese(II) were yellow and light pink solids respectively. The magnetic susceptibility data for all five compounds could be fitted to the Weiss-Curie Law and had very small negative φ values suggesting weak antiferromagnetic interactions between the paramagnetic ions.

The magnetic susceptibility of Eu2RuH6 below 77 K

Abstract Magnetic susceptibility measurements for Eu2RuH6 at temperatures as low as 7 K are interpreted as (1) confirming a previous inference of ferromagnetic behavior, (2) indicating a Curie temperature of 29 K and (3) suggesting a reduction in the amount of EuO impurity. Eu2RuH6 remains structurally intact after exposure to hydrogen at 700 atm and 250°C. The amount of EuO observed in the X-ray diffractograms of Eu2RuH6 is substantially less after exposure to a high pressure of hydrogen.

Low temperature magnetic behavior of some quaternary metal hydrides

Abstract The magnetic behavior of the mixed metal quaternary hydrides [Sr2−xEux]RuH6, [Ca2−xEux]RuH6, and [Sr2−xEux]IrH5 where 0⪕x⪕2 has been studied at low temperatures. Susceptibility measurements were made by the Faraday body force method at temperatures from 10 K to room temperature and at magnetic fields from 200 to 8350 Gauss. Ferromagnetic Curie temperatures were observed for all europium containing samples and ranged from 29 K for Eu2RuH6 to less than 10 K for samples in which x = 0.5. Values of the magnetic moments, Weiss-Curie constants and the Curie temperatures for different compositions are reported and discussed.

Magnetic susceptibility of the TaV2/H2 system

Abstract The magnetic susceptibility exhibited by the ordered (C-15) and random bcc allotropes of TaV 2 decreases linearly with increasing hydrogen content. However, the susceptibility exhibited by the (C-15) form is about four times more sensitive to hydrogen than that exhibited by the bcc form. The results are in qualitative accord with the thermodynamics of hydrogen solution.