Eur. Phys. J. B 1, 439-452 (1998)
https://doi.org/10.1007/s100510050207

Interplay between chains of S=5/2 localised spins and two-dimensional sheets of organic donors in the synthetically built magnetic multilayer λ-(BETS)₂F_eCl₄

¹ Laboratoire de Physique de la Matière Condensée (UMR CNRS 5830) , SNCMP, INSA, Complexe Scientifique de Rangueil, 31077 Toulouse Cedex, France
² Centre de Recherches Paul Pascal, CNRS, avenue du Dr. Schweitzer, 33600 Pessac, France
³ Electrotechnical Laboratory, Tsukuba, Ibaraki 305, Japan
⁴ Laboratoire de Physique Quantique (UMR CNRS 5626) , IRSAMC, Université P. Sabatier, route de Narbonne, 31062 Toulouse Cedex, and Institut Laue Langevin, BP 156, 38042 Grenoble Cedex 9, France
⁵ Department of Physics, State University of New York, Buffalo, New York 14260, USA
⁶ Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
⁷ Department of Chemistry, Faculty of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan
⁸ Institute for Molecular Science, Nishigo-naka 38, Myodaiji, Okasaki 444, Japan
⁹ Laboratoire de Chimie de Coordination, CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France

Corresponding author: ^a brossard@insa-tlse.fr

Received: 6 August 1997
Accepted: 10 November 1997
Published online: 15 February 1998

Abstract

In order to understand the magnetic field-induced restoration of a highly conductive state in λ-(BETS)₂F_eCl₄, static (SQUID) and dynamic (ESR and AFR) magnetization measurements were performed on polycrystalline samples and single crystals, respectively. In addition, cantilever and resistivity measurements under steady fields were performed. While the metal-insulator transition curve of the (T, B) phase diagram exhibits a first order character, a "spin-flop" transition line divides the insulating state when the magnetic field is applied along the easy axis of magnetization. The effects of a RKKY-type indirect exchange and of applied magnetic field are described within the framework of a generalized Kondo lattice, namely two chains of S=5/2F_e³⁺localised spins coupled through the itinerant spins of the 2D sheets of BETS. The calculations, which can incorporate intramolecular electron correlations within a mean field theory, are in qualitative agreement with the field induced transition from the antiferromagnetic insulating ground state to a canted one, i.e. a not fully oriented paramagnetic, but metallic state.