Phase separation behaviour on κ-(BEDT-TTF)2Cu[N(CN)2]Br

Abstract

The system of the deuterated κ-(BEDT-TTF-d[n,n]) 2 Cu[N(CN) 2 ]Br is situated in the critical region between the superconducting(SC) phase and the antiferromagnetic insulator (AFI) phase, and is just on the Mott type critical boundary of paramagnetic metal (PM) phase and paramagnetic insulator (PI) phase. We perform two single-crystal 13 C-NMR studies on the non and the fully deuterated κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br at low temperature with the applied field 9.4T. We found two new experimental results. One is that the phase separation is found in κ-(BEDT-TTF-d[0,0]) 2 Cu[N(CN) 2 ]Br salt, like partially deuterated κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br salt. The other is that the phase separation is observed at around T* with the applied field parallel to the conducting layer, unlike partially deuterated κ-(BEDT-TTF-d[n,n]) 2 Cu[N(CN) 2 ]Br. The former result suggests the field induces AF transition. the latter result suggests there is the field direction dependence of the M-I phase separation behavior in κ -(BEDT-TTF-d[4,4]) 2 Cu[N(CN) 2 ]Br.