Volume dependence of magnetic hyperfine fields in Eu-intermetallic compounds

Abstract

High-pressure M\"ossbauer studies on $^{151}\mathrm{Eu}$ intermetallics (Eu${\mathrm{Al}}_{2}$, Eu${\mathrm{Al}}_{4}$, Eu${\mathrm{Cu}}_{2}$, Eu${\mathrm{Cu}}_{5}$, Eu${\mathrm{Sn}}_{3}$, ${\mathrm{Eu}}_{0.5}$${\mathrm{Yb}}_{0.5}$${\mathrm{Sn}}_{3}$, Eu${\mathrm{Zn}}_{2}$, and Eu${\mathrm{Pt}}_{2}$) provide information about the volume dependence of the effective hyperfine field ${B}_{\mathrm{eff}}$ at the ${\mathrm{Eu}}^{2+}$ nucleus. These measurements have been performed at 4.2 K and pressures up to 65 kbar. The results show that (i) the volume dependence of the transferred hyperfine field ${B}_{\mathrm{thf}}$ is the dominating contribution to $\frac{\ensuremath{\partial}{B}_{\mathrm{eff}}}{\ensuremath{\partial}\mathrm{ln}V}$; (ii) the magnitude of $\frac{\ensuremath{\partial}{B}_{\mathrm{thf}}}{\ensuremath{\partial}\mathrm{ln}V}$ can be explained only if one assumes the participation of $s$, $p$, and $d$ conduction electrons in the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction responsible for ${B}_{\mathrm{thf}}$; and (iii) the exchange integrals for non-$s$ conduction electrons (${J}_{p,f}$ and/or ${J}_{d,f}$) are more sensitive to volume changes than that for $s$ conduction electrons (${J}_{s,f}$).