The European Physical Journal B (EPJ B)

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Eur. Phys. J. B 7, 9-17

$\mathsf\!Al}$ Nuclear Magnetic Resonance studies of $\mathsf{CeAuAl_$

P. Vonlanthen - J.L. Gavilano - B. Ambrosini - H.R. Ott

Laboratorium für Festkörperphysik, Eidgenössische Technische Hochschule-Hönggerberg, 8093 Zürich, Switzerland
ott@solid.phys.ethz.ch

Received: 5 May 1998 / Received in final form: 16 July 1998 / Accepted: 20 July 1998

Abstract
We report $\rm }\!Al$ Nuclear Magnetic Resonance studies of CeAuAl₃ and LaAuAl₃ at frequencies between 1.30 and 76.91 MHz and at temperatures from $45\;\mathrm{mK}$ up to $320\;\mathrm{K}$ . CeAuAl₃ is a new heavy-electron compound which orders antiferromagnetically at $1.32\;\mathrm{K}$ . For the two inequivalent Al sites of CeAuAl₃, the transferred hyperfine couplings $H_{{hf}}=1.91~\mathrm{kOe}/ \mu_}$ and $H_{{hf}}=2.40~\mathrm{kOe}/ \mu_}$ are relatively small compared to those in other Ce compounds. The nuclear quadrupolar coupling constants e²qQ/h are 2.9 MHz and 7.8 MHz, respectively. We suggest that the magnetic structure of the ordered state below $1.32\;\mathrm{K}$ is of a simple spiral type with the ordered Ce moments arranged ferromagnetically within the (ab) planes of the tetragonal crystal lattice. Based on this magnetic structure we estimate a 25% reduction of the Ce moments, most likely due to Kondo screening. At high temperatures, in the paramagnetic state of CeAuAl₃, the spin-lattice relaxation rate T₁^-1 is dominated by the fluctuations of the localised Ce moments. At $20\;\mathrm{K}$ , T₁^-1 is $96 ~\mathrm{s}^$ , more than two orders of magnitude larger than for the reference compound LaAuAl₃. For temperatures lower than $20\;\mathrm{K}$ T₁^-1 decreases as a function of (T/H) and below $1\;\mathrm{K}$ , displays a linear-in-T behaviour, strongly enhanced compared to the reference compound LaAuAl₃.

PACS
75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions - 75.30.-m Intrinsic properties of magnetically ordered materials - 76.60.-k Nuclear magnetic resonance and relaxation

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