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The dodecaboride LuB12 with cage-glass state and rattling modes has been studied to clarify the nature of the large amplitude vibrations of Lu ions. Discovered anisotropy of charge transport in conjunction with distortions of the conventional fcc symmetry of the crystal lattice may be attributed to coherent motion of Lu ions along singular direction in the lattice. Arguments are presented in favor of cooperative dynamic Jahn-Teller effect in the boron sublattice to be the reason of the rattling mode, lattice distortion and formation of the filamentary structure of the conductive channels. PACS numbers: 61.66.Fn, 72.15.Gd:

The magnetic properties of CoSi single crystals have been measured in a range of temperatures T = 5.5-450 K and magnetic field strengths H ≤ 11 kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility χ(T) = M(T)/H to be determined for a hypothetical "ideal" (free of magnetic impurities and defects) CoSi crystal. The susceptibil ity of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The χ(T) value sig nificantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest tem peratures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been sepa rated and taken into account in the calculations of χ(T).

AC magnetic susceptibility of a single crystal of MnSi was measured along the ferromagnetic phase-transition line up to a pressure of 0.8 GPa created by compressed helium. The results show that the tricritical point is situated at much lower pressure and at significantly higher temperature (P tr ∼ = 0.355 GPa, T tr ∼ = 25.2 K) than was reported previously (∼ 1.2 GPa, ∼ 12 K). These new observations put certain constraints on the origin of the tricritical point in MnSi. PACS numbers: 62.50.+p, 64.60.Kw, 75.30.Kz Recently, there has been a considerable interest in studying the magnetic phase transition in the intermetallic compound MnSi [1,2,3,4,5,6,7,8,9,10,11], which reveals weak ferromagnetic properties slightly below 30 K with spins having been ordered into a long wavelength helical structure [12,13]

High-quality single crystals of LuB are grown using the induction zone melting method. The x-ray data are collected at temperatures 293, 135, 95, 50 K. The crystal structure of LuB can be refined with record low R-factor in the cubic Fm [Formula: see text] m symmetry group despite reiterated observations of the cubic symmetry distortions both in the unit-cell values and in the physical properties. A peculiar computing strategy is developed to resolve this contradiction. True symmetry of the electron-density distribution in LuB is proved to be much lower than cubic as a result, which correlates very accurately with anisotropy of transport properties of LuB.

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Electron spin resonance (ESR) in strongly correlated metals is an exciting phenomenon, as strong spin fluctuations in this class of materials broaden extremely the absorption line below the detection limit. In this respect, ESR observation in CeB6 provides a unique chance to inspect Ce3+ magnetic state in the antiferroquadrupole (AFQ) phase. We apply the original high frequency (60 GHz) experimental technique to extract the temperature and angular dependences of g-factor, line width and oscillating magnetization. Experimental data show unambiguously that the modern ESR theory in the AFQ phase considering the Γ8 ground state of Ce3+ ion completely fails to predict both the g-factor magnitude and its angular dependence. Alignment of the external magnetic field along [100] axis induces a strong (more than twofold) broadening of ESR line width with respect to the other crystallographic directions and results also in the anomalous temperature dependences of the g-factor and oscillating magnetization. In this experimental geometry the latter parameter surprisingly exceeds total static magnetization by 20% at T* ~ 2.5 K. We argue that the unusual physical picture of ESR in CeB6 may be strongly affected by spin fluctuations and dynamic collective effects predominantly pronounced in [100] direction.

Samples of MnGe and CoGe having cubic B20 structure were prepared at high pressure. Magnetic measurements showed that CoGe is a Pauli paramagnet, but MnGe exhibits antiferromagnetic-type ordering below TN = 175 K. The magnetic susceptibility of MnGe follows a Curie-Weiss law above 300 K with an effective magnetic moment µeff = 3.68 µB/f.u. and θp = + 231 K. The large positive value of θp indicates a strong ferromagnetic exchange. The value of the effective moment is close to the free Mn4+ ion (4F3/2) value 3.87 µB/f.u. From measurements of the magnetization of MnGe in fields up to 60 kOe and in the temperature range 2-350 K, we constructed its T-H magnetic phase diagram which is similar to that proposed for MnSi-type compounds with helical magnetic order. Specific heat measurements reveal that the total magnetic entropy of MnGe relative to nonmagnetic CoGe is equal to 3.55 J/mole-K (0.62Rln2).