NMR/NQR Study of pressure-induced superconductor CePt2In7

Zero-field In-115-nuclear magnetic resonance (NMR) has been used to study single crystals of CePt2In7, which is a heavy-fermion antiferromagnet with a Neel temperature (T-N) of 5.2 K at ambient pressure. The NMR spectra under zero field near the 3 nu(Q) line of the orthorhombic In(3) sites are taken at 1.6 K under hydrostatic conditions at ambient pressure and 2.4 GPa. These data reveal the coexistence of commensurate and incommensurate antiferromagnetic (AFM) orders at ambient pressure and that the commensurate ordering is stabilized by increasing pressures. The nuclear spin-lattice relaxation rates (1/T-1) for In(3) sites indicate the localized nature of f electrons far above T-N. The values of 1/T-1 in the paramagnetic state decrease by applying pressure. In contrast, the residual values of 1/T-1 much below T-N increase by pressure.