Pólya urn with memory kernel and asymptotic behaviors of autocorrelation function

Magnetic susceptibility and torque measurements have been performed for neutral BEDT-TTF crystals to investigate the diamagnetic properties. The diamagnetic susceptibility is found to be anisotropic at room temperature, -1.9 × 10^-4 emu=mol for the magnetic field H || [011] and −2.5 × 10−⁴emu=mol for H || [100], comparable to the Langevin diamagnetism estimated from the Pascal constants, −2.04 × 10⁻⁴emu=mol. The diamagnetism for both directions is gradually enhanced with decreasing temperature. Sinusoidal torque curves are clearly observed for two field rotations in the (011) and (100) planes, reflecting the anisotropic diamagnetism of the neutral BEDT-TTF molecule. The results show that careful attention must be paid to quantitative discussion of the torque signals in various organic materials.