Magnetic properties of GdMg

The lattice constants at room temperature and the magnetic properties of several members of the series Gd_χLa_{1- χ}Mg were studied in the temperature range 4.2-300 K with applied fields up to 340 kG. Several of the pseudo-binary compounds were found to give rise to antiferromagnetic ordering in low applied fields. In their magnetic isotherms at 4.2 K critical fields occur which are associated with the destruction of the antiferromagnetic ground state. These critical fields were found to increase with La concentration. It is shown that in Gd_χLa_{1- χ}Mg the antiferromagnetic interaction between the Gd spins decreases with increasing χ whereas the ferromagnetic interaction increases in the same sense. In GdMg the antiferromagnetic interaction has almost completely vanished, so that superficially this compound looks like a normal ferromagnet.