Extended stability range of the non-Fermi liquid phase in UCoAl.

High pressure was used to investigate the stability of the non-Fermi liquid (NFL) state, observed in electrical resistivity of uranium-based band metamagnet UCoAl in a pure form (paramagnet) or with Fe substitution (ferromagnetic ground state), both in a single-crystal form. By combining the pressure variations of magnetization and resitivity in these materials the phase diagram for UCoAl had been constructed. The band metamagnet transforms into the ferromagnetic state as the critical metamagnetic field is reduced to zero by the lattice expansion analogous to the negative pressure. Within the same diagram, the increasing hydrostatic pressure drives the critical metamagnetic field upwards while reducing the magnetization increment at the transition. The NFL state persists to about 4-5 GPa. Although spin fluctuations play an important role in the character of UCoAl, they do not exhibit any criticality in the sense of divergence of parameters describing the resistivity around the Ferro-NFL phase transition, which is of the first order type.

The effect of hydrogenation on magnetic interactions in CeNi.

The crystal structure and magnetic properties of CeNiH(3.7) were studied by means of powder x-ray diffraction, specific heat, and dc and ac magnetization techniques. It was established that hydrogenation stabilizes the 4f(1) state of Ce and turns CeNi-H into a dilute Kondo system with T(K) = 3.7 K. The Kondo screening in CeNiH(3.7) is suppressed by the applied magnetic field, although it still affects the properties of CeNiH(3.7) at 14 T, as indicated by the enhanced γ-coefficient of electronic specific heat, which remains more than twice as large as in the precursor compound CeNi. Its zero-field value is as high as 1890 mJ (mol K(2))(-1). Hydrogenation acts primarily as the negative pressure agent in CeNiH(3.7), while the role of H-metal bonding is secondary.

Disordered states in IPA-Cu(ClxBr1-x)3 induced by bond randomness.

The mixtures of two spin-gap compounds IPA-Cu(ClxBr1-x)3 are studied by electron paramagnetic resonance and magnetization processes [M(H)]. From electron paramagnetic resonance spectra, the symmetry of the spin-gap state breaks down, even for x=0.99. From M(H) curves for x=0.95 and 0.92, however, spin gaps survive below mu0Hc1=10+/-1 T, and the M(H) slopes bend at mu0Hc3=40+/-1 T, below the saturation field Hc2. Such a curvature suggests an exotic phase transition: Bose-Einstein condensation of spin triplets occurs at Hc1