%0 Journal Article
%T Paramagnetic Metal¡ªAntiferromagnetic Insulator Transition in ¦Ð-d System ¦Ë-BETS2FeCl4, BETS = Bis(ethylenedithio)tetraselenafulvalene
%A Hiroshi Akiba
%A Kazuo Shimada
%A Naoya Tajima
%A Koji Kajita
%A Yutaka Nishio
%J Crystals
%D 2012
%I MDPI AG
%R 10.3390/cryst2030984
%X Quasi-two-dimensional organic conductor ¦Ë-BETS 2FeCl 4 (BETS = bis(ethylenedithio)tetraselenafulvalene) transforms from a paramagnetic metal (PM) to an antiferromagnetic insulator (AFI) at a transition temperature, T MI, of 8.3 K under zero magnetic field. To understand the mechanism of this PM-AFI phase transition, we studied the thermodynamic properties of ¦Ë-BETS 2FeCl 4. We observed, below T MI, a six-level Schottky hump in its specific heat and a broad shoulder in its magnetic susceptibility. Just below the transition temperature T MI, about 80% of 3 d spin degree of freedom is sustained. These temperature dependences clarify that ¦Ð and 3 d spins do not cooperatively form the AF order at T MI. In ¦Ë-BETS 2Fe xGa 1£¿xCl 4 system, the increasing Fe 3 d spin density enhances the internal magnetic field caused by ¦Ð spin antiferromagnetic (AF) ordering, although the 3 d spin itself maintains large entropy against the AF ordering. It was confirmed that the Fe 3 d spin provided favorable conditions for this mysterious PM-AFI phase transition in the ¦Ð electron system. We propose that this phase transition originates from the magnetic anisotropy introduced by the ¦Ð- d interaction, which suppressed the low dimensional fluctuation in the ¦Ð spin system.
%K organic conductor
%K ¦Ð-d interaction
%K PM-AFI phase transition
%K specific heat
%K magnetic susceptibility
%U http://www.mdpi.com/2073-4352/2/3/984