O. P. Matveev, A. M. Shvaika
Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine,
1 Svientsitskii St., UA--79011 Lviv, Ukraine
The Hubbard model for small size clusters is investigated. Using direct diagonalization of the small cluster Hamiltonian, electronic, magnetic and spin susceptibilities are calculated and their behavior at low temperature is investigated. The temperature behavior of susceptibilities for two- and three-site clusters is investigated for both center and edge of the Brillouin zone. If at the given concentration the ground state is polarized, the susceptibilities diverge following the Curie law and the system is transformed into the magnetically ordered state at $T=0$.
PACS number(s): 71.10.Fd, 72.10.Di, 74.25.Kc