Low-temperature properties of quasione-dimensional magnetic systems

Detailed analysis of low-temperature properties of quasi-one-dimensional magnetic systems with a non-symmetrical half filling of the energetic band ($\mu\neq 0$, $\mu$ being the deviation from the half filling of the band) is carried out. It is shown that in such a system the coexistence of superconductivity (SC) and spin density wave (SDW) is possible. The behaviour of the system essentially depends on the theory parameters $\mu$ and $t=T_{c0}/T_{s0}$. Depending on the values of these parameters the following situations are possible: 1) SC and SDW coexist in a large temperature region $0<T<T_c$ $(T_c\sim T_s)$; 2) SC and SDW coexist in a small temperature region near $T=0$; 3) the appearance of SC in $T=T_{c1}$ and its vanishing in $T=T_{c2}$, i.e. the reentrance of the system in the normal state with a diminishing temperature, is observed.