Persistence of a non-antiphase modulated magnetic structure to in the heavy electron compound

¹ Commissariat à l'Energie Atomique, DRECAM/SPEC 91191 Gif-sur-Yvette, France
² Université de Nancy I - 54506 Vandoeuvre-lès-Nancy, France
³ Commissariat à l'Energie Atomique, DRFMC/SPSMS 38054 Grenoble Cedex 9, France
⁴ II. Physikalisches Institut, Universität zu Köln Zülpicher Str. 77, 50937 Köln, Germany
⁵ Max Planck Institut for Chemical Physics of Solids 1187 Dresden, Germany

Received: 28 March 2000
Accepted: 5 June 2000

Abstract

Measurements by ¹⁷⁰Yb Mössbauer spectroscopy down to 0.025 K and by neutron diffraction down to 1.7 K have been performed in the heavy electron compound YbPtAl (). At 0.025 K, the Mössbauer spectrum evidences a non-square modulation of the magnetic moment, incommensurate with the lattice spacings. This is the first clear example of a Kramers local moment Yb-based system where the Kondo singlet ground state allows a modulated magnetic structure to persist to  K. The 3rd- and 5th-order harmonics of the modulation could be measured, and their thermal variation was followed from 0.025 K to 5 K. An abrupt decrease of both harmonics at 3 K is concomitant with a peak in the specific heat, suggesting a first-order phase transition where the modulation transforms into a pure sine wave.