The intermetallic compounds of rare earths with non-magnetic metals exhibit
a large variety of magnetic behaviours arising from the competition of Ion
a-range exchange interactions between 4f ions in the presence of magnetocry
stalline anisotropy. This competition results in frustrated magnetic states
such as collinear incommensurate, helimagnetic, fan, long-period commensur
ate or antiphase structures. The anisotropy plays a crucial role in the exi
stence and temperature dependence of these structures, according to the uni
axial (Ising-like) or planar (XY) character of the compounds, as well as to
the Kramers or non-Kramers type of the rare earth. In some peculiar situat
ions, mixed magnetic structures may even occur at low temperature, where tw
o kinds of equivalent magnetic sites coexist, with a high- and a low-moment
state, respectively. The addition of antiferroquadrupolar coupling may als
o favour multiaxial, multi-Q antiferromagnetic structures, in particular in
cubic systems. In all these cases, applying a magnetic field results in ma
gnetization processes showing a metamagnetic behaviour, with the presence o
f one or several well-defined plateaus separated by more or less sharp tran
sitions. A thorough microscopic analysis of all these phenomena can be carr
ied out by using an appropriate model, such as the self-consistent periodic
field model. A few examples will illustrate the various effects of frustra
tion in these intermetallic magnetic systems. (C) 2001 Elsevier Science BY
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