Magnetic properties of R ions in R${\mathrm{Co}}_5$ compounds (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er)

The values of the R-Co exchange field ${\mathit{H}}_{\mathrm{ex}}$ and the crystalline-electric-field parameters ${\mathit{A}}_{\mathit{n}}^{\mathit{m}}$ at the rare-earth (R) site in R${\mathrm{Co}}_5$ (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er) and ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Nd}}_{\mathit{x}}$${\mathrm{Co}}_5$ (x=0.5, 0.6, 0.8, and 1.0) compounds are evaluated by a comparison of calculations with a series of experiments. The experiments provide the following data: temperature dependence of spontaneous magnetization of the compounds and magnetic moment of the rare-earth ion, magnetization curves along the crystallographic axes, and temperature dependence of the easy direction of magnetization. The anisotropies of the R-Co exchange interaction and the magnetic moment of the Co sublattice are taken into account in the calculation. The R-Co exchange field ${\mathit{H}}_{\mathrm{ex}}$ decreases monotonically across the rare-earth series from Pr to Er. For ${\mathrm{PrCo}}_5$, the value of ${\mathit{A}}_2^0$ is much smaller than those of the other compounds, which suggests valence fluctuations for the Pr ion. For ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Nd}}_{\mathit{x}}$${\mathrm{Co}}_5$ and ${\mathrm{SmCo}}_5$, the absolute value of ${\mathit{A}}_2^0$ decreases with increasing temperature.