Magnetic properties of rare--Earth--Iron intermetallic compounds

Curie points, the temperature dependence of the high-field magnetization below room temperature, saturation moments, and densities are reported for the most iron-rich compounds in the rare earth-iron systems. The heavy rare earth compounds have the composition A
2
Fe
14
and the hexagonal Th
2
Ni
17
-type structure, while the light rare earths have the stoichiometry AFe
7
and a modified rhombohedral Th
2
Zn
17
structure. From the saturation of Y
2
Fe
17
and Lu
2
Fe
17
, an iron moment of
2.0\mu_{B}
is calculated. In these two compounds and in CeFe
7
, PrFe
7
, and, perhaps, NdFe
7
, all atomic moments couple ferromagnetically, while for Gd
2
Fe
17
through Tm
2
-Fe
17
the magnetizations of the rare earth and iron sublattices subtract. Curie temperatures range from -180°C (CeFe
7
) through a peak of +186°C (Gd
2
Fe
17
) to -41°C (Tm
2
Fe
17
). This suggests that two exchange mechanisms are active which make comparable contributions to the interaction energy: direct exchange between Fe atoms and indirect coupling via conduction electrons between iron and the rare earth atoms.