Effect of pressure on the Curie temperature of annealed Fe-Ni-Cr-Mo-Si-B amorphous alloys

Effect of high pressure on the Curie temperature of annealed Fe₃₀Ni3₆Cr₁₂Mo₂Si₅B₁₅ amorphous alloys has been investigated. It has been shown that the annealed samples e hibit a smaller pressure dependence ofT _c than as-quenched one.Dedicated to Dr. S. Krupika on the occasion of his 65th birthday.We would like to thank Dr. P. Duhaj (Institute of Physics, Slovak Academy of Sciences, Bratislava) for the preparation of amorphous samples and Mrs. H. Kuchárska for technical assistance.     

Group extensions and tame pairs

Tame pairs of groups were introduced to study the missing boundary problem for covers of compact 3-manifolds. In this paper we prove that if is an exact sequence of infinite finitely presented groups or if is an ascending HNN-extension with base and is a certain type of finitely presented subgroup of , then the pair is tame.

Also we develop a technique for showing certain groups cannot be the fundamental group of a compact 3-manifold. In particular, we give an elementary proof of the result of R. Bieri, W. Neumann and R. Strebel:

A strictly ascending HNN-extension cannot be the fundamental group of a compact 3-manifold.

     

Ascending Hnn Extensions of Finitely Generated Free Groups Are Hopfian

It is shown that every ascending HNN extension of a finitelygenerated free group is Hopfian. An important ingredient inthe proof is that under certain hypotheses on the group H, ifG is an ascending HNN extension of H, then cd(G) = cd(H) + 1.     

Homotopy of ends and boundaries of CAT(0) groups

For n ≥ 0, we exhibit CAT(0) groups that are n-connected at infinity, and have boundary which is (n − 1)-connected, but this boundary has non-trivial nth-homotopy group. In particular, we construct 1-ended CAT(0) groups that are simply connected at infinity, but have a boundary with non-trivial fundamental group. Our base examples are 1-ended CAT(0) groups that have non-path connected boundaries. In particular, we show all parabolic semidirect products of the free group of rank 2 and have a non-path connected boundary.     

Tame Combings of Groups

In this paper, we introduce the idea of tame combings for finitely presented groups. If is a closed irreducible 3-manifold and is tame combable, then the universal cover of is homeomorphic to . We show that all asynchronously automatic and all semihyperbolic groups are tame combable.

     

Evidence for direct and indirect gap in FeSi from electron tunneling spectroscopy

We report electron tunneling spectroscopy studies on single crystalline FeSi sample performed for the case of homogeneous tunnel junction (TJ) contacts and for the case of counter electrodes made from Pt-Rh alloy. Our results reveal that while the tunneling spectroscopy in the configuration with Pt-Rh tip is preferably sensitive to the d-partial density of states (DOS) and to the indirect energy gap, the FeSi-FeSi type of TJ yields spectroscopic information on the c-partial DOS and on the direct gap in FeSi.     

The Separation of Platinum Group Metals (PGM) in Chloride Media by Isothiouronium Resins

Styrene-divinylbenzene copolymers incorporating isothiourea functional groups show a remarkable affinity for platinum-group-metal (PGM) ions in chloride media, The mode of ion binding to the resin depends on the equilibria between isothiourea (free base) form and isothiouronium (conjugated acid) form, This in return is related to matrix structure, A. resin, Monivex, which shows high binding capacities for PGM ions in high acidities (2–6M HC1) is described. Equilibrium, rate and selectivity data, as well as process application data is presented and discussed, Electron microprobe studies are used to follow chemical changes in resin beads and ion regeneration patterns.     

Exchange bias in bulk layered hydroxylammonium fluorocobaltate (NH?OH)?CoF?

The magnetic properties of layered hydroxylammonium fluorocobaltate (NH(3)OH)(2)CoF(4) were investigated by measuring its dc magnetic susceptibility in zero-field-cooled (ZFC) and field-cooled (FC) regimes, its frequency dependent ac susceptibility, its isothermal magnetization curves after ZFC and FC regimes, and its heat capacity. Effects of pressure and magnetic field on magnetic phase transitions were studied by susceptibility and heat capacity measurements, respectively. The system undergoes a magnetic phase transition from a paramagnetic state to a canted antiferromagnetic state exhibiting a weak ferromagnetic behavior at T(C) = 46.5 K and an antiferromagnetic transition at T(N) = 2.9 K. The most spectacular manifestation of the complex magnetic behavior in this system is a shift of the isothermal magnetization hysteresis loop in a temperature range below 20 K after the FC regime-an exchange bias phenomenon. We investigated the exchange bias as a function of the magnetic field during cooling and as a function of temperature. The observed exchange bias was attributed to the large exchange anisotropy which exists due to the quasi-2D structure of the layered (NH(3)OH)(2)CoF(4) material.