Magnetic properties and resonance studies of some pseudobinary gadolinium or yttrium compounds

The magnetic measurements and resonance studies on pseudobinary cubic compounds suggest that the 3d electrons of transition metal atoms do not share a common 3d band. Although the magnetic properties of pseudobinary rare-earth (yttrium)-transition metal (T) compounds of R@kTT -3,-type have been studied generally [l] we have no information on the individual magnetic behaviour of T' and T atoms. In order to obtain further data on this matter we have investigated Gd(CoxNil -3, and R(Fe,T, -,), compounds, where R = Gd or Y and T = Co, Ni, Mn or Al. To determine the separate magnetic contributions from the transition metal atoms, we make two assumptions : (a) The Mossbauer effect measurements can indirectly supply information on the iron magnetic contribution. This can be justified analysing the data plotted in figure 1. The hyperfine field per unit spin (H,,/MFe) is the same for a wide range of MFe values and also for various types of crystalline structures. (b) Nickel has no magnetic moment in system as in case of RNi, compounds. The magnetic measurements, ferromagnetic and electron paramagnetic resonance studies, in a large temperature range show some interesting features : $ 1 . 2 5 1 ~ ~ ~ ~ 2 --AI I 200 250 300 3 50 Mean hyperfine f~eld (kGs) Fig. 1. The relationship between FeS7 hyperfine field values and the iron moments. Fig. 2. The composition dependence of the Co and Fe moment per atom in R(Fe,Co,-,), compounds and Fe,Co, -, solid solutions. (I) The composition dependence of the magnetic moment of T' and T atoms behave in a different manner. We present in figure 2 as an example the magnetic moment of Fe and Co atoms in R(F~,CO,-~), compounds, as well as in Fe,Co, -x solid solutions [2]. The composition dependence of mean cobalt moment in R(FexCol-,), compounds can be analysed in the local environment model, considering the interactions with the next neighbours (NN) iron atoms. The results of experimental data are well described if we suppose that cobalt has a magnetic moment Mco (x = 1 ) if there are at least n, = 2 iron atoms as NN in 3m site or Mco ( x = 0) if n, < 2. These data suggest that the magnetic interactions involving cobalt atoms are essentially of short-range. The observed peak in the composition dependence of the transition metal sublattice is attributed only to the magnetic behaviour of iron. The composition dependence of Fe moment in R(FexT; -3, where T' = Al, Ni, Mn, can be justified only if we consider the magnetic interactions with the atoms of more than one coordination shell, these interactions being also dependent on the distances between atoms. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979567 MAGNETIC PROPERTIES AND RESONANCE STUDIES OF GADOLINIUM OR YTTRIUM COMPOUNDS C5-185 (11) The reciprocal susceptibility for T > Tc in case of ferromagnetic compounds follows a Curie Weiss behaviour, while in case of ferrimagnetic compounds a hyperbolic variation is observed figure 3. The ratio between the number of spins determined from the Curie constant and that obtained from saturation measurements is dependent on the Curie temperature following the trend reported previously [3].