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 $T=0$.
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机译：研究了小型集群的Hubbard模型。利用小簇哈密顿量的直接对角线化，计算了电，磁和自旋磁化率，并研究了它们在低温下的行为。对于布里渊区的中心和边缘，研究了两点和三点簇的磁化率温度行为。如果在给定的浓度下基态是极化的，则磁化率遵循居里定律发散，并且系统在$ T = 0 $时转变为磁有序状态。
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