High field magnetization of (Benzo-TTFVS)2FeBr4and (Benzo-TTFVO)2FeBr4

We performed high field magnetization measurements up to 55 T for newly synthesized antiferromagnetic charge-transfer salts, (Benzo-TTFVS)2FeBr4 with TN = 5.8 K and (Benzo-TTFVO)2FeBr4 with TN = 9.3 K. A spin-flop behavior at 1.8 T and a saturation at 14.8 T were observed in the magnetization curve at 0.5 K for the (Benzo-TTFVS)2FeBr4 salt. For the (Benzo-TTFVO)2FeBr4salt a spin-flop at 6.9 T and a saturation at 36.2 T were observed. We estimate the exchange interaction between d spins and the magnetic anisotropy for both salts from the magnetization data.