Spin gap of a pressure-induced superconductor Sr2Ca12Cu24O41 at an optimum pressure of 3.8 GPa Original Research Article

Nuclear magnetic resonance (NMR) on 63Cu nuclei was performed in a pressure-induced superconductor Sr2Ca12Cu24O41 at an optimum pressure of 3.8 GPa. A pressure of 3.8 GPa was achieved by improving a piston-cylinder-type pressure cell and developing a NMR probe with a steady-load control system. We found that the spin gap still exists even at the optimum pressure. The spin gap was almost the same at pressures below 3.5 GPa on the pressure–temperature phase diagram, whereas it decreased rather drastically above 3.5 GPa.