Antiferromagnetic Ordering in the Spin Singlet State of the Ladder/Chain Material:Sr_<2.5>Ca_<11.5>Cu_<24>O_<41>

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XVe report on specific heat and neutron scattering uneastrrenaents perfornaed forSrtv .Cl.CU24O4] sinule crvstals. The sr>ecific heat data of SI2.5C2l1l.5CLl24O41 showed a sharpphase transition at T?;2.1 K, indicating the possible onset of a lonag-range order. Specific heatrneastrrements under naagnetic fields also revealed that this phase transition is not dtre to chargeordering or structural phase trarusition but to magnetic ordering. In the netttron scattering experiments, we observed sexzeral Bragg peaks, corresponding to the taaagnetic ordering observed inthe specific heat rtaeastrrements. Furthertaaore, we confirnaed frona polarized neutron scatternngnaeasureunents that these Bragg peaks are undoubtedly tnagnetic in origin. Considering both thenuclear magnetic resonance srnd neutron scattering data, a jcossible rnagnetic strtrcttrre on thechain and ladder sites has been proposed. In this system, the singlet state and antiferrornagneticorder induced by appropriate hole-doping coexist at atmbient presstrre and the dissolved holepairs move trnder high presstrre, leading to the occurrence of strpercondtrctivity.
社団法人日本物理学会の論文
1999-07-15