The compound, Nd 7 Rh 3 , crystallizing in Th 7 Fe 3 -type hexagonal structure, was previously known to exhibit two magnetic transitions, one at 32 and the other at 10 K (in zero magnetic field).Here, we report the existence of a field-induced first-order antiferromagnetic-to-ferromagnetic transition at 1.8 K in this compound. On the basis of the measurements of isothermal magnetization and magnetoresistance, we provide evidence for the occurrence of "kinetic hindrance", proposed in the recent literature, resulting in phase-coexistence ("super-cooled" ferromagnetic + antiferromagnetic) and percolative electrical conduction in this stoichiometric intermetallic compound. A point of emphasis, as inferred from ac susceptibility data, is that such a co-existing phase is different from spin-glasses, thereby clarifying a question raised in the field of 'phase-separation'. PACS numbers:75.30. Kz, 64.60.My, 75.90.+w 1

The first heavy fermion superconductor CeCu 2 Si 2 has not revealed all its striking mysteries yet. At high pressures, superconductivity is supposed to be mediated by valence fluctuations, in contrast to ambient pressure, where spin fluctuations most likely act as pairing glue. We have carried out a multiprobe (electric transport, thermopower, ac specific heat, Hall and Nernst effects) experiment up to 7 GPa on a high-quality CeCu 2 Si 2 single crystal. For the first time, the resistivity data make it possible quantitatively to draw the valence crossover line within the p-T plane and to locate the critical end point at 4.5 ± 0.2 GPa and a slightly negative temperature. In the same pressure region, remarkable features have also been detected in the other physical properties, presumably acting as further signatures of the Ce valence crossover and the associated critical fluctuations: We observe maxima in the Hall and Nernst effects and a sign change and a strong sensitivity on magnetic field in the thermopower signal.

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The temperature dependent ac and dc magnetization and heat capacity data of Ca3CoIrO6, a spin-chain compound crystallizing in a K4CdCl6-derived rhombohedral structure, show the features due to magnetic ordering of a frustratedtype below about 30 K, however without exhibiting the signatures of the so-called "partially disordered antiferromagnetic structure" encountered in the isostructural compounds, Ca3Co2O6 and Ca3CoRhO6. This class of compounds thus provides a variety for probing the consequences of magnetic frustration due to topological reasons in stoichiometric spinchain materials, presumably arising from subtle differences in the interchain and intrachain magnetic coupling strengths. This compound presents additional interesting situations in the sense that, ac susceptibility exhibits a large frequency dependence in the vicinity of 30 K uncharacteristic of conventional spin-glasses, with this frustrated magnetic state being robust to the application of external magnetic fields.

We report an unusual temperature (T) dependent electrical resistivity (rho) behavior in a class of ternary intermetallic compounds of the type RCuAs2 (R=rare earths). For some rare earths (Sm, Gd, Tb, and Dy) with negligible 4f hybridization, there is a pronounced minimum in rho(T) far above respective Néel temperatures (T(N)). However, for the rare earths which are more prone to exhibit such a rho(T) minimum due to 4f-covalent mixing and the Kondo effect, this minimum is depressed. These findings, difficult to explain within the hitherto-known concepts, present an interesting scenario in magnetism.