A. Blaise

Iridium(VI) stabilized in a perovskite-type lattice: Ba2CalrO6

Abstract For the first time iridium(VI) was stabilized in an octahedral site of the perovskite lattice Ba2CaIrO6 using optimized structural and chemical bonding factors and oxygen pressure. The stabilization of this unusual oxidation state was inferred from chemical analysis, structural and magnetic measurements and from 193Ir Mossbauer study.

Magnetic properties of ErRu2Si2, ErOs2Si2 and DyRu2Si2

Abstract ErRu 2 Si 2 , ErOs 2 Si 2 and DyRu 2 Si 2 have been investigated by magnetization, neutron diffraction and Mossbauer measurements. These intermetallics were shown to order magnetically at low temperature and to exhibit metamagnetic-like behaviour. ErRu 2 Si 2 if T N = 5.7 K and ErOs 2 Si 2 ( T N = 4.7 K ) present sine-modulated magnetic structures characterized by a wavevector Q = ( q x , 0, 0) with q x = 1 5 (Ru) and 5 17 (Os). In both compounds the moments are aligned along the b -axis and a partial squaring of the modulation was inferred from Mossbauer and neutron diffraction measurements performed at 1.6 K. DyRu 2 Si 2 orders at T N = 29 K with a sine-wave modulation, Q = ( 2 9 , 0, 0) , of the moments parallel to the c -axis. A squaring up of the magnetic occurs at about 19 K it is complete at 1.6 K where μ Dy = 10 μ B , in agreement with the Mossbauer data.

Magnetic properties of ErPd2Si2 from magnetization Mössbauer and neutron diffraction measurements

Abstract Magnetization, neutron diffraction and 166 Er Mossbauer measurements on ErPd 2 Si 2 are reported. Below 4.8 K ErPd 2 Si 2 orders AF with complex modulated magnetic structures, where the Er moments are aligned along the c -axis. At 1.5 K a squared structure with μ Er ≈ 7.8(1)μ B is found while a saturation Er moment of 8.2(2)μ B is inferred from the hyperfine field data. The temperature dependence of the Mossbauer spectra in the paramagnetic region is explained in the framework of a relaxation model implying excited crystal field levels. Its analysis is used to estimate the B m n CEF parameters.

Magnetic properties of DyIr2Si2 and ErIr2Si2

Abstract DyIr 2 Si 2 and ErIr 2 Si 2 (ThCr 2 Si 2 structure type) have been investigated by magnetization, neutron diffraction and Mossbauer measurements with the 166 Er and 193 Ir resonances. These intermetallics were shown to order antiferromagnetically at 40 K (Dy) and 10 K (Er) and to exhibit metamagnetic behaviour. The AF order is of type I for both compounds, with the Dy moments (10μ B ) pointing along the c -axis and the Er moments (8.76μ B ) in the basal plane.

Magnetic susceptibility of α-plutonium

Abstract We have measured the magnetic susceptibility of very pure α-plutonium metal between 4.6 and 300 K. At temperatures higher than 80 K, χ is found to be constant. But at lower temperatures, χ goes through a minimum near 40 K. Below 40 K, the data are used to fit a model. χ = χ o + C T - θ p In view of the results we can say that an electronic transition occurs around 60 K, and describe it as follows: 5f electrons are condensed and this gives rise to localized moments. But they appear to be disordered down to 4.6 K.

Magnetic properties of DyIr2Si2(I) from Mössbauer spectroscopy and magnetisation measurements

Abstract DyIr 2 Si 2 (ThCr 2 Si 2 structure type) has been investigated by magnetisation measurements and by Mossbauer spectroscopy with the 161 Dy and 193 Ir resonances. The compound was shown to order antiferromagnetically at 40 K and to exhibit metamagnetic-like behaviour. The analysis of the 161 Dy hyperfine interaction data allowed to estimate the crystal ( B 0 2 , B 0 4 ) and molecular field parameters. The Dy moments of 10μ B were shown to point along the tetragonal c -axis. From the absence of any transferred field at the 193 Ir nuclei it was anticipated that DyIr 2 Si 2 orders with a type I antiferromagnetic structure.

Magnetic properties of ErPt2Si2

Abstract ErPt2Si2(CaBe2Ge2 structure type) has been shown to remain paramagnetic down to 1.5 K. From the analysis of the slow relaxing Mossbauer spectra observed in the paramagnetic state it was concluded that the Er moment associated with the ground state amounts to 8.25(20)μB. This value is very close to the full moment of 9μB for Er3+ ions.