LADDER ISING SPIN CONFIGURATIONS .1. HEAT-CAPACITY

We consider a ladder Ising spin model (with two coupled Ising spin cha ins), characterized by two couplings (interchain and intrachain coupli ngs), to study in detail, in an analytical way, its thermal behaviour and particularly the variation of the specific heat versus temperature , the ratio of interaction constants, and the magnetic field. It is in teresting that when the competition between interchain and intrachain interactions is strong the specific heat exhibits a double peak and wh en the competition is not so strong the specific heat has a single pea k. Further, without entering into details, we give, in a numerical way , some similar results for more complicated ladder configurations (wit h more than two linear Lsing chains). The spin-1/2 ladders or systems of spin chains may be realized in nature by vanadyl pyrophosphate ((VO )(2)P2O7) or similar materials. All these intermediate systems are tod ay important to gain further insight into the physics of one-dimension al spin chains and two-dimensional high-T-c spin systems, both of whic h have shown interesting and unusual magnetic and superconducting prop erties. It is plausible that experimental and theoretical studies of l adders may lead to other interesting physical phenomena.