New magnetic phase in rb3c60 fullerene in normal state observed in torque experiments

For the first time, magnetic properties of fullerides have been studied using a torque technique. Rb3C60 single crystal has been investigated in these experiments. It was shown that this method is sensitive to the structural phase transition from s.c. to f.c.c. structure. A rearrangement of magnetic system in this material was observed at temperature T ~ 200 - 250 K. Our results clearly show, that this effect is a crossover to an ordered magnetic phase related to interaction of magnetic dipoles and is related to the distorted T' site. The effect is discussed in terms of cooperative Jahn-Teller effect.