The physical properties of many of the rare-earth intermetallic compounds have been collected together. They are discussed in terms of the role that the magnetic exchange and crystal field interactions play in determining these properties. It is pointed out that in this vast number of materials there is an ideal chance of establishing which of several second-order terms are effective in determining structural stability.

Intermetallic rare-earth compounds.

A review is given of the magnetic properties of metallic actinides, and of the relationship between their properties and their electronic structures. It is shown that the 5f electrons of light actinides often form into bands, rather than exist as localised electrons as is usually the case for the 4f electrons of metallic rare earths. The 5f bands form due to 5f-5f wavefunction overlap or to hybridisation with s, p or d electrons. As a result of the band formation, a wide variety of magnetic phenomena may occur. These range from non-magnetic transition-metal behaviour, to spin fluctuations and itinerant magnetism, as well as localised 5f electron magnetism.

https://iopscience.iop.org/article/10.1088/0034-4885/41/10/001/pdf

Magnetic properties of the actinide elements and their metallic compounds

Magnetization study of UFe2

The authors report self-consistent energy band calculations for UFe2 and UCo2 in four approximations: both semi-relativistic and fully relativistic for the paramagnetic ground states; both spin-polarised and spin-polarised with spin-orbit coupling included self consistently for the ferromagnetic ground state of UFe2. They compare ab initio calculated and measured lattice constants, bulk moduli, linear specific heat coefficients, pressure dependence of the magnetic moment and magnetic form factor. UCo2 is found to be an enhanced paramagnet and UFe2 an itinerant ferromagnet with a magnetic moment due mainly to the iron moments. However, the magnetism on the uranium sites is unusual in that they calculate both spin and orbital contributions to the moment that are large, antiparallel and almost equal.

Chemical bonding and magnetism in 3d-5f intermetallics

The spin density distributions in two alloys of iron and silicon (approximate compositions Fe3Si and Fe4Si) have been determined by polarized neutron diffraction. The observed data have been corrected for the effects of extinction and have been analysed by the standard Fourier method and also by expressing the density distribution in terms of spherical harmonics. The latter method of analysis indicated a non-centrosymmetric density around one of the iron sites and an explanation for this has been suggested in terms of a change of sign with distance for the s-d exchange interaction.

http://iopscience.iop.org/article/10.1088/0305-4608/2/2/026/pdf

Spin density distribution in iron-silicon alloys

A study has been made by the diffraction of polarized neutrons of a single crystal of the ferromagnetic compound UFe2 at 84°K (T/TC = 0.49). The flipping ratios of all reflections out to a sinθ/λ value of 0.41 A−1 have been measured. These measurements show that, at this temperature, the Fe atom has a magnetic moment of 0.38 μB and that there is a small but significant moment of the U atom, parallel to the Fe moment, of about 0.03 μB. The spin density distribution at the U atom position is very nearly spherically symmetric, but the spin density at the Fe site is seen to have large deviations from spherical symmetry, being elongated in the direction of the cube edges and contracted along the nearest‐neighbor connecting line. Good agreement between observed and calculated structure factors is obtained by using a shallow form factor of the 5f3 type for the U moment, and by using an Fe form factor calculated on the basis of 65% of the magnetic electrons having Eg symmetry and 35% T2g symmetry.

M. Yessik

Papers

Magnetic Structure and Spin‐Density Distribution in UFe2