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We have developed high-pressure NMR technique with an Indenter Cell using NiCrAl alloy. It was designed to set easily into a conventional dilution fridge and/or high field magnet. We have succeeded in 7Li-NMR measurement of a heavy fermion spinel LiV2O4 in T-range between 60 mK and 30 K under pressure up to 4.7 GPa. At ambient pressure, 1/T1 shows a broad maximum around 50 K and is proportional to the temperature below 6 K. This is quite similar to the relaxation behavior in f-electron HF systems. However, 1/T1T becomes larger with applying higher pressure below 10 K and does not obey T1T = constant relation down to 1 K. Knight shift K, meanwhile, is independent of pressure above 2 GPa, indicating that the uniform component of susceptibility χ(0) does not change under high pressure. Some antiferromagnetic fluctuations with wave vector q ≠ 0 dominate relaxation rate in LiV2O4 near the boundary of the pressure induced insulating phase.

Experimental techniques on production of ultra-high pressure at very low temperature, electrical resistance and magnetization measurement are developed for the purpose of searching for pressure-induced superconductivity in some simple systems. Previous results of pressure induced superconductivity of I, Br, Ca, SnI4 and C6I4O2 are reviewed and remaining problems are discussed shortly. Recent findings of metallization and superconductivity of O and S are also reported.