The dependence on pressure (P ) and field (H ) of the magnetic phase diagram of MnSi has been investigated by means of measurements of the AC susceptibility (χ ) up to 16 kbar and 7 T at temperatures down to 30 mK. For ambient pressure, we report on a peak in χ above T c at a characteristic temperature T m that rises quickly with field. The pressure dependence of T m is found to be strongly analogous to that of the zero-field transition to long-range order at T c . Features of χ in the field versus temperature (T ) phase diagram may be viewed as 'fingerprint' evidence of a field-induced crossover at T m of the itinerant magnetism from a non-polarized regime at high T and low H to a polarized regime at low T and high H . The long-wavelength spin spiral, present at low H , appears to be supported only in the polarized regime, so in the immediate vicinity of the critical pressure P c for which T c → 0, a small pocket exists as a re-entrant state.

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We report the novel pressure(P ) -temperature(T ) phase diagram of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3 revealed by the 115 In nuclear-spin-lattice-relaxation (T1) measurement. In the itinerant magnet CeRhIn5, we found that the Néel temperature TN is reduced at P ≥ 1.23 GPa with an emergent pseudogap behavior. In CeIn3, the localized magnetic character is robust against the application of pressure up to P ∼ 1.9 GPa, beyond which the system evolves into an itinerant regime in which the resistive superconducting phase emerges. We discuss the relationship between the phase diagram and the magnetic fluctuations.PACS numbers: PACS: 74.25. Ha, 74.62.Fj, 74.70.Tx, 75.30.Kz, 76.60.Gv It has been reported that a superconducting (SC) order in cerium (Ce)-based heavy-fermion (HF) compounds takes place nearby the border at which an antiferromagnetic (AF) order is suppressed by applying pressure (P ) to the HF-AF compounds CeCu 2 Ge 2 ,[1] CePd 2 Si 2 [2] and CeIn 3 [3]. The superconductivity in these compounds, however, occurs only in extreme conditions where the pressure exceeds ∼ 2 GPa and temperature (T ) is cooled down below ∼ 1 K. Indeed the experiments were restricted mainly to transport measurements. The discovery of P -induced HF superconductors in Ce-based HF-AF compounds has stimulated further experimental works under P [4,5,6,7]. In order to gain profound insight into a relationship between magnetism and superconductivity in HF systems, systematic NMR/NQR experiments under P are important, since they can probe the evolution of the magnetic properties toward the onset of SC phase.Recently, Hegger et al. found that a new HF material CeRhIn 5 consisting of alternating layers of CeIn 3 and RhIn 2 reveals an AF-to-SC transition at a relatively lower critical pressure P c = 1.63 GPa than in all previous examples [1,2,3]. The SC transition temperature T c = 2.2 K is the highest one to date among P -induced superconductors [4]. This finding has opened a way to investigate the P -induced evolution of both magnetic and SC properties over a wide P range. In the previous paper [7], the 115 In NQR study of CeRhIn 5 has clarified the P -induced anomalous magnetism and unconventional superconductivity. In the AF region, the Néel temperature T N exhibits a moderate variation, while the internal field H int at 115 In(1) site in the CeIn 3 plane due to the magnetic ordering is linearly reduced in P = 0 -1.23 GPa, extrapolated to zero at P * = 1.6 ± 0.1 GPa. This P * is comparable to P c = 1.63 GPa at which the SC signature appears [4], which was indicative of a second-order like AF-to-SC transition rather than the first-order one suggested previously [4]. At P = 2.1 GPa, it was found that the nuclear spin-lattice relaxation rate 1/T 1 reveals a T 3 dependence below the SC transition temperature T c , which shows the existence of line-nodes in the gap function [7]. It is, however, not yet clear how the electronic states change with P when the AF phase evolves into the SC phase.On the other hand, CeIn 3 c...