W. Suski

Structure and magnetic properties of UFe10Si2 and UFe10Mo2

Abstract New intermetallic compounds UFe 10 Si 2 and UFe 10 Mo 2 have been obtained. They exhibit the tetragonal ThMn 2 -type crystal structure. Both compounds are ferromagnetic, below about 700 and 250 K for UFe 10 Si 2 and UFe 10 Mo 2 , respectively.

Formation of a heavy fermion phase in UCu4+xAl8−x by variation of stoichiometry

Abstract Progressive substitution of Cu for Al in UCu 4+ x Al 8 −x yields as increasing compression of the unit cell. This results in a reduction of the Neel temperature from ifT N = 42 K for x = 0 to ifT N = 15 K for x = 1.0. No magnetic ordering is found for x ⩾ 1.5. Rather the T -dependence of the resistivity shows a maximum in the range 6 to 15 K and indicates the formation of a Kondo-lattice state. The latter is characterized by heavy fermions (γ( T a0)≅0.8 J/K 2 mol for x = 1.75).

Structural and magnetic properties of Lu2Fe17Hx (x=0; 3) single crystals

Abstract The structural and magnetic characterization of Lu2Fe17Hx (x=0; 3) single crystals is presented. The host alloy crystallizes with a disordered variant of hexagonal (Th2Ni17-type P63/mmc) structure. It is observed that the host alloy symmetry is retained upon hydrogenation. Hydrogen is found to be accommodated in the rare earth-rich octahedral position. The Neel temperature of the hydride Lu2Fe17H3 is increased by 35 K per hydrogen atom. The magnetization and magnetic anisotropy constant remains practically unaffected in the hydride Lu2Fe17Hx at x=3.

Magnetic properties and 57Fe Mössbauer effect investigation in U1−xYxFe10Si2 solid solutions

Abstract The solid solutions U1−xYxFe10Si2 have been studied by means of X-ray diffraction, 57Fe Mossbauer effect and magnetic investigations. In the intermediate concentration range, a redistribution of the iron and silicon atoms over non-equivalent positions was observed despite the fact that both ternaries have similar occupancies in all positions. Such a redistribution could be a reason for the slight non-linearity observed in the concentration dependences of lattice parameters and magnetic properties. The results of a hyperfine field study were used to estimate the uranium magnetic moment in UFe0Si2, which is about 0.5μB and coupled ferromagnetically with the iron sublattice magnetic moment.

Crystal structure and magnetic properties of UFe4Al8

Abstract A new ternary intermetallic compound UFe 4 Al 8 was prepared. X-ray analysis showed that the compound crystallizes in the body-centred tetragonal ThMn 12 -type structure. The space group is I 4/ mmmm and the unit cell contains two formula units. The magnetization was measured in high fields up to 140 kOe and in the temperature range 4.2–300 K, and the magnetic susceptibility was measured in the temperature range 4.2–300 K.

Magnetic properties of UMvAl12−v (M ev Fe, Cu) Intermetallics

Magnetic properties of UFevAl12−v (3.2 ⩽ v ⩽ 4.8) and UCu4.5Al7.5 have been investigated at temperatures from 4.2 to 300 K and in magnetic fields up to 140 kOe. The compounds with iron evhibit a ferromagnetic character, whereas UCu4.5Al7.5 seems to be antiferromagnetic below 30 K. Between 40 and 180 K the susceptibility of this compound follows a Curie-Weiss law with gv = −138 K and μeff = 3.11 μB. We have failed to detect the 63Cu nuclear magnetic resonance. Results are discussed in terms of the possible contribution of the uranium atom to magnetic order.

Neutron diffraction studies of the structural and magnetic properties of AnFe4Al8 (An Th, U, Np) intermetallic compounds

Abstract AnFe4Al8 intermetallic compounds crystallize isostructurally in the tetragonal space group I4/mmm. Lattice parameters, atomic positions and bond distances have been determined by powder neutron diffraction for An  Th, U, Np. At low temperatures, the iron sublattices are antiferro-magnetically ordered in identical G-type spin configurations with spin orientations along the c axis and moment values of 0.7, 1.0 and 1.1 μ b for the thorium, uranium and neptunium compounds respectively. In UFe4Al8 and NpFe4Al8 there is an additional ferromagnetic order of the An sublattices with moment values of 0.8 and 0.6 μ b for the uranium and neptunium ions respectively. Al(3p)-Fe(3d) band hybridization is concluded to play a dominant role in establishing the magnetic structure.

Magnetic properties of the UFenAl12−n (n=4, 5 or 6) and ThFe4Al8 intermetallic compounds

Abstract Magnetic behaviour of the ThFe4Al8 and UFe4Al8 intermetallic compounds has been discussed in comparison with that of isomorphous rare earth RFe4Al8 compounds. Magnetic properties of new uranium intermetallics UFe5Al7 and UFe6Al6 have been presented, as well.

57Fe Mössbauer effect in UFexAl12−x system

Abstract 57 Fe Mossbauer effect examinations were carried out on UFe x Al 12− x alloys with x = 4, 5 and 6 in the temperature range 14–370 K. The spectra for x =5 and 6 can be fitted with the Fe atoms distributed over the 8( f ), 8( j ) and 8( i ) positions, whereas for x =4 the Fe atoms are located at the 8( f ) sites only, in agreement with earlier results. The hyperfine fields corresponding to the three sites ( f, j, i ) are 54%, 43% and 3% for x =5 and 58%, 35% and 7% for x =6 respectively. The Curie points determined from H hf ( T ) plots are 162, 265 and 350 K for x =4, 5 and 6 respectively, in fair agreement with the results of magnetic examinations.

The discovery of the ferromagnetism in U(H, D)3: 40 years later

Abstract A historical view of the discovery of the ferromagnetism in U(H, D) 3 , the results of more than 40 years of studies of these compounds and the consequences of this discovery on the development of the investigations of other actinide compounds are presented.