We present NMR data in the normal and superconducting states of CeCoIn5 for fields close to Hc2(0)= 11.8 T in the ab plane. Recent experiments identified a first-order transition from the normal to superconducting state for H > 10.5 T, and a new thermodynamic phase below 290 mK within the superconducting state. We find that the Knight shifts of the In(1), In(2) and the Co are discontinuous across the first-order transition and the magnetic linewidths increase dramatically. The broadening differs for the three sites, unlike the expectation for an Abrikosov vortex lattice, and suggests the presence of static spin moments in the vortex cores. In the low-temperature and highfield phase the broad NMR lineshapes suggest ordered local moments, rather than a long wavelength quasiparticle spin density modulation expected for an FFLO phase.PACS numbers: 71.27.+a, 74.70.Tx, 75.20.Hr One of the most intriguing properties observed in Kondo lattice systems is the emergence of unconventional superconductivity near a quantum critical point (QCP). By varying some external parameter such as field or pressure, an antiferromagnetic ground state can be tuned such that the transition temperature goes to zero at the QCP. As the tuning parameter increases past the QCP, conventional Fermi-liquid behavior is recovered below a characteristic temperature T FL [1]. Superconductivity often emerges as the ground state of the system for sufficiently low temperatures in the vicinity of the QCP [2]. The heavy-fermion superconductor CeCoIn 5 exhibits many properties typical of a Kondo lattice system at a QCP. In particular, T FL appears to vanish at the superconducting critical field H c2 (T = 0) for fields along the c axis, suggesting the presence of a field-tuned QCP [3,4]. This interpretation has remained contentious because the ordered state associated with the QCP is superconductivity rather than antiferromagnetism. One explanation is that an antiferromagnetic (AFM) phase is hidden within the superconducting phase diagram, which is the genitor of both the QCP and non-Fermi liquid behavior in the vicinity of H c2 (0). However, when the superconductivity is suppressed with Sn doping, the QCP tracks H c2 (0), and no magnetic state emerges in the phase diagram, whereas pressure separates the QCP [5].In fact, there is a field-induced state, which we will refer to as the B phase, in the H − T phase diagram of CeCoIn 5 that exists just below H c2 (0). The order parameter of the B phase could be either (1) a different symmetry of the superconducting order parameter, (2) a fieldinduced magnetic phase, or (3) a Fulde-Ferrell-LarkinOvchinnikov (FFLO) superconducting phase [6,7,8,9]. The normal to superconducting transition in this system has a critical point at (H, T ) ∼ (10.5T, 0.75K), separating a second to first order transition, and the B phase exists below a temperature T 0 (H) ∼ 290 mK and is bounded by T c (H). NMR experiments suggest the presence of excess quasiparticles associated with nodes in the superconducting FFLO wavefunction [10,11,1...

The heavy fermion superconductor CeCoIn 5 can be tuned between superconducting and antiferromagnetic ground states by hole doping with Cd. Nuclear magnetic resonance data indicate that these two orders coexist microscopically with an ordered moment 0:7 B . As the ground state evolves, there is no change in the low-frequency spin dynamics in the disordered state. These results suggest that the magnetism emerges locally in the vicinity of the Cd dopants.

A Raman spectroscopic study of the high-frequency optical phonons in single crystals of the multiferroic system RMn 2 O 5 ͑R = Bi, Eu, Dy͒ was performed. All studied materials show anomalous phonon shifts, below a new characteristic temperature for these materials, T * ϳ 60-65 K. The sign and magnitude of such shifts appear to be correlated with the ionic radius of R, envolving from softenings for R = Bi to hardenings for R = Dy and showing an intermediary behavior for R = Eu. Additional phonon anomalies were identified below ϳT N ϳ 40-43 K, reflecting the onset of long-range ferroelectric and/or magnetic order of the Mn sublattice. Complementary dc-magnetic susceptibility ͓͑T͔͒ measurements for BiMn 2 O 5 up to 800 K yield a Curie-Weiss temperature CW = −253͑3͒ K, revealing a fairly large frustration ratio ͉͑ CW ͉ / T N = 6.3͒. Deviations of ͑T͒ from a Curie-Weiss paramagnetic behavior due to magnetic correlations were observed below temperatures of the order of ͉ CW ͉, with the inverse susceptibility showing inflection points at ϳ160 K and ϳT *. Supported by ͑T͒ data, the anomalous Raman phonon shifts below T * are interpreted in terms of the spinphonon coupling, in a scenario of strong magnetic correlations. Overall, these results support significant magnetic frustration, introduce a new characteristic temperature ͑T * ͒, and suggest a surprisingly rich behavior for the magnetic correlations in the paramagnetic phase of this system.

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