M. Orendac et al., ON THE MAGNETIC-PROPERTIES OF THE LOW-DIMENSIONAL MAGNET CU(C2H8N2)(2)NI(CN)(4), Journal of magnetism and magnetic materials, 140, 1995, pp. 1645-1646
Specific heat measurements performed from 80 mK to 2 K have revealed t
hat Cu(C2H8N2)(2)Ni(CN)(4) behaves as a S = 1/2 2D AF Heisenberg syste
m. A transition to the magnetic ordered state was observed at (128 +/-
2) mK. The ESR measurements at 4.2 K support the assumption that the
low-temperature properties are influenced by the Jahn-Teller effect.