A COUPLED METAL-INSULATOR AND ANTIFERROMAGNETIC TRANSITION OF LAMBDA-(BETS)(2)FECL4 UNDER HIGH-PRESSURE AND MAGNETIC-FIELD [BETS = BIS(ETHYLENEDITHIO)TETRASELENAFULVALENE]

The magnetoresistance of lambda-(BETS)(2)FeCl4 was measured along the needle axis of the crystal to determine the pressure and magnetic held dependences of the coupled metal-insulator and antiferromagnetic tran sition temperature (T-MI, T-N) T-MI decreases when applying pressure a nd/or magnetic field. The T-MI vs H curve shows an inflection point (H -1). The anomaly observed around 1 T (H-1) corresponds to the spin-flo p transition observed by the SQUID measurements. The magnetization (M) of the oriented polycrystalline sample of lambda-(BETS)(2)FeCl4 was m easured at 2-15 K in a magnetic field of 0.01-7 T. The magnitude of th e characteristic drop of M observed for the field parallel to the c ax is (Delta M-parallel to) becomes small above 1.2 T but remains almost constant above 4.5 T. (C) 1998 Elsevier Science Ltd.