J. Phys. I France
Volume 3, Numéro 5, May 1993
Page(s) 1235 - 1244
DOI: 10.1051/jp1:1993268
J. Phys. I France 3 (1993) 1235-1244

Structural and magnetic investigations of the Peierls transition of $\alpha$-(Per) $_{\rm {2}}$M(mnt) $_{\rm {2}}$ with M = Fe and Co

V. Gama1, R. T. Henriques1, M. Almeida1, C. Bourhonnais2, J. P. Pouget3, D. Jérôme3, P. Auhan-Senzier3 and B. Gotschy3

1  Laboratorio Nacional de Engennaria e technologia Endustrial, Departamento de Quimica, P- 2685 Sacavem, Portugal
2  Dtpartement de physique, Universitt de Sherhrooke, Sherbrooke, Qutbec, JIK 2R1, and Laboratoire de Physique des Solides (CNRS URA 2), Universitt de Paris-Sud, Bstiment 510, Orsay, F-91405, France
3  Laboratoire de Physique des Solides (CNRS URA 2), Universitt de Paris-Sud, Batiment 510, Orsay, F-91405, France

(Received 18 September 1992, revised 7 January 1993, accepted in final form 16 January 1993)

In this work we present and discuss the temperature variation of X-ray, EPR and nuclear spin-lattice relaxation rate measurements for the two quasi-one-dimensional compounds $\alpha$-(Per) $_{\rm {2}}$Fe(mnt) $_{\rm {2}}$ and $\alpha$-(Per) $_{\rm {2}}$Co(mnt) $_{\rm {2}}$. From X-ray and EPR intensity data, a Peierls instability of the Perylene stacks is found to take place at 58 K and 75 K for the Fe and Co derivatives respectively. In contrast to other members of this series of two-chain compounds, the M(mnt) $_{\rm {2}}$, stacks are found to play no role in the Peierls instability. As for diffusive excitations of localized spins in dimerized Fe(mnt) $_{\rm {2}}$, stacks, their influence is shown to dominate the temperature variation of both the spin-lattice nuclear relaxation rate and the previously measured Faraday spin susceptibility.

76.30P - 76.60E - 61.65

© Les Editions de Physique 1993