Magnetic properties of very dilute Pd(Gd) alloys

Abstract

Measurements of the magnetic moment $\ensuremath{\sigma}(H, T)$ of ${\mathrm{Pd}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}$ alloys were made for $0.0003\ensuremath{\le}x\ensuremath{\le}0.02$ in applied fields $H$ up to 215 kG and for $1.3\ensuremath{\le}T\ensuremath{\le}4.2$ K. The data were analyzed using four different formulas which permitted extrapolation of $\ensuremath{\sigma}$ to very large fields so that the saturation moment ${\ensuremath{\mu}}_{s}$ and matrix susceptibility ${\ensuremath{\chi}}_{\mathrm{mat}}$ could be determined. Detailed data analysis shows that: (a)${\ensuremath{\mu}}_{s}\ensuremath{\simeq}\frac{7{\ensuremath{\mu}}_{B}}{(\mathrm{Gd} \mathrm{atom})}$ for all the alloys studied, (b) ${\ensuremath{\chi}}_{\mathrm{mat}}\ensuremath{\le}{\ensuremath{\chi}}_{\mathrm{Pd}}$ for all the alloys and (c) the Gd moment is more difficult to saturate at large $x$. The most satisfactory fits to the data were obtained with the expression $\ensuremath{\sigma}={\frac{\ensuremath{\alpha}H}{{[H(H+{H}_{0})]}^{\frac{1}{2}}}}{B}_{\frac{7}{2}}(J\ensuremath{\beta}{[H(H+{H}_{0})]}^{\frac{1}{2}})+{\ensuremath{\chi}}_{\mathrm{mat}}H$, where $\ensuremath{\alpha}$, $\ensuremath{\beta}$, ${H}_{0}$, and ${\ensuremath{\chi}}_{\mathrm{mat}}$ are fitted parameters and ${B}_{\frac{7}{2}}(y)$ is the Brillouin function for $J=\frac{7}{2}$. A model is presented in which ${(H{H}_{0})}^{\frac{1}{2}}$ is associated with an average anisotropy-like field transverse to the applied field. A paramagnetic Curie temperature is extracted from the parameter $\ensuremath{\beta}$, which also includes $s\ensuremath{-}f$ exchange effects. Some discrepancies with previously published results are discussed.