Experimental and theoretical study of extremely dilute Sc and Fe impurities in Gd and Tb

Abstract

We have carried out in-beam time-differential perturbed angular distribution experiments on Fe implanted into single-crystal Gd and Tb hosts, where it is found to occupy both substitutional and interstitial sites. For comparison, the simpler systems Sc in Gd and Tb were also studied. Calculations of the local electronic structure, magnetic moments, and hyperfine fields ${\mathit{B}}_{\mathrm{hf}}$ were performed using the real-space LMTO-ASA method for Fe at both sites in Gd and for Sc in Gd, which implants substitutionally. The results of the experiments and calculations of ${\mathit{B}}_{\mathrm{hf}}$ at 0 K agree well and permit a qualitative explanation of the local magnetism. The calculations show an antiferromagnetic coupling of the local Fe moments to the host moments in Gd which is confirmed by the experiments; it persists to temperatures well above ${\mathit{T}}_{\mathit{C}}$. The temperature dependence of ${\mathit{B}}_{\mathrm{hf}}$ and the damping of the spin-rotation spectra are also discussed.