Torsion studies of relaxation magnetic effects in C₆₀ fullerite in magnetic field

Highly sensitive torsion technique was used in dynamic low-frequency (0.1–1 Hz) oscillatory and static (without oscillations) experiments to study temperature dependences of the magnetic properties of C₆₀ fullerite in the magnetic fields transverse and longitudinal with respect to the oscillation axis. The temperature position of observed oscillation attenuation peaks that are related with phase transitions depends on the direction in which temperature changes (cooling or heating). The most clearly pronounced transitions accompanied by reorientation of magnetic dipole moments have been observed in the region of the structural (Fm3m–Pa3) transition at Т ≈ 260 K and at temperatures Т ≈ 180–200 K. The region of “chaos” has been discovered where magnetic properties and the direction of the “spontaneous” rotation of the fullerite specimen with respect to magnetic field change rapidly. We have shown that under certain conditions the relaxation time of the magnetic moments of molecular rotators, after elapsing of which the fullerite specimen experiences multiple changes in its rotational movement direction, if temperature increases from 77 K to 280 K, coincides with the “magic” time that was observed in static experiments at room temperatures Т = 295 K. An assumption has been made that the phenomena observed are related with relaxation processes in the rotational subsystem of molecular C₆₀ rotators and with the magnetic flux trapped by fullerite.