RT Journal Article
T1 Electric field gradients in the rare earth–aluminium compounds RAl₂ and RAl₃ studied by ^(111)Cd perturbed angular correlations
A1 Forker, F.
A1 Presa Muñoz De Toro, Patricia Marcela De La
AB Perturbed angular correlation (PAC) spectroscopy has been used to investigate the electric field gradient (EFG) at the probe nucleus ^(111)In/^(111)Cd in the paramagnetic phase of the rare earth (R)-aluminium compounds RAl₂ for all R elements and Y and in RAl₃ for R=Gd,Tm,Yb,Lu. The nuclear electric quadrupole interaction (QI) between the EFG and the ^(111)Cd quadrupole moment was measured as a function of temperature in the range T_c < T ≤ 1200 K. In the second half of the RAl₂ series and in the RAl₃ compounds, except for YbAl₃, the quadrupole frequency v_q shows the monotonous decrease with increasing temperature normally observed with closed-shell probe nuclei in metallic systems. In the early members of the RAl₂ series, however, v_q (T) passes through a maximum at T similar to 300 K. It is proposed that this unusual behavior reflects a contribution of the 4f shell of the R constituents to the EFG at the Al site which is quenched at higher temperatures by thermal averaging of the 4f quadrupole moment. In the intermediate-valence compound YbAl₃ the temperature dependence of the QI exhibits a shallow maximum which can be related to the temperature variation of the 4f hole occupation. Furthermore the PAC spectra provide information on the site preference of the ^111In solutes in RAl₂ for different R constituents and temperatures. In two-phase samples containing RAl₂ and RAl₃ with AuCu₃ structure, at T < 900 K the solutes show a very pronounced preference for the Al site of RAl₃, but at higher temperatures they migrate to the Al site of RAl₂. Jumps of the ^(111)In/ ^(111)Cd probes on the Al sublattice of RAl₃ compounds with AuCu₃ structure (R=Tm,Yb,Lu) lead to nuclear spin relaxation of ^(111)Cd. The temperature dependence of the relaxation rates shows an Arrhenius behavior with jump activation enthalpies E_(A)=1.6(1) eV for R=Tm, Lu and E_(A)=1.2(1) eV for R=Yb.
PB American Physical Society
SN 1098-0121
YR 2007
FD 2007-09
LK https://hdl.handle.net/20.500.14352/52150
UL https://hdl.handle.net/20.500.14352/52150
LA eng
NO © 2007 American Physical Society.The authors gratefully acknowledge financial support by Deutscher Akademischer Austauschdienst (DAAD), Germany. The x-ray characterization of the RAl₃ compounds has been carried out by H. Euler at Mineralogisch-Petrologisches Institut, University of Bonn.
NO Deutscher Akademischer Austauschdienst (DAAD), Germany
DS Docta Complutense
RD 5 abr 2025