Three kinds of cupric spin ladder compounds, SrCu203(2-1eg), Sr2Cu3Os(3-1eg), and LaCuOzs(2-1eg), have been discovered in the course of studies of high-pressure chemistry carried out at 6 GPa and 1200 K, typically. Structures, electrical and magnetic properties of these intriguing compounds, which exemplify the initial stage of the transition from one-to two-dimensionality, will be summarized.
High-pressure synthesis at 1 ~ 10 GPa is a rather classical but still promising way to discover new compounds. Using a cubic anvil type apparatus mainly, the author's group has carried out for about eight years a systematic research at 6 GPa and 1200 K, typically, and it has been shown that various new complex cupric oxides crystallizing in low-dimensional structures can be obtained by quenching. The densities of these compounds are, as a matter of course, higher than those of the corresponding ambient-pressure phases or phase mixtures. These are metastable (therefore difficult to obtain with the usual preparative methods) mainly because of an energy increase at the counter:cation site as will be suggested below, but in fact we have had little problems with storage and handling for structural and physical measurements. This paper will first describe a typical high-pressure effect on the phase formation and next structural and physical properties of three "spin ladder" compounds discovered relatively recently.