Jiakui K. Wang

High hardness in the biocompatible intermetallic compound β-Ti3Au

A remarkable fourfold increase in hardness of titanium is achieved by the addition of gold, yielding a novel biocompatible material. The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.

Discovery of Spin Glass Behavior in Ln2Fe4Sb5 (Ln = La–Nd and Sm)

Single crystals of Ln(2)Fe(4)Sb(5) (Ln = La-Nd and Sm) were grown from an inert Bi flux. Measurements of the single crystal X-ray diffraction revealed that these compounds crystallize in the tetragonal space group I4/mmm with lattice parameters of a ≈ 4 Å, c ≈ 26 Å, V ≈ 500 Å(3), and Z = 2. This crystal structure consists of alternating LnSb(8) square antiprisms and Fe-sublattices composed of nearly equilateral triangles of bonded Fe atoms. These compounds are metallic and display spin glass behavior, which originates from the magnetic interactions within the Fe-sublattice. Specific heat measurements are void of any sharp features that can be interpreted as contributions from phase transitions as is typical for spin glass systems. A large, approximately linear in temperature, contribution to the specific heat of La(2)Fe(4)Sb(5) is observed at low temperatures that we interpret as having a magnetic origin. Herein, we report the synthesis, structure, and physical properties of Ln(2)Fe(4)Sb(5) (Ln = La-Nd and Sm).

An itinerant antiferromagnetic metal without magnetic constituents.

E. Svanidze, Jiakui K. Wang, T. Besara, L. Liu, Q. Huang, T. Siegrist, B. Frandsen, J. W. Lynn, Andriy H. Nevidomskyy, Monika Barbara Gamża, M. C. Aronson, Y. J. Uemura and E. Morosan 1 Department of Physics and Astronomy, Rice University, Houston, TX, 77005 USA 2 National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32306 USA 3 Department of Physics, Columbia University, New York, New York 10027, USA 4 NIST Center for Neutron Research, National Institute of Standards and Technology, MD 20899, USA 5 Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973 USA 6 Department of Physics, Royal Holloway, University of London, Egham, TW20 0EX, UK and 7 Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794 USA

Topological metal behavior in GeBi2Te4 single crystals

The metallic character of the GeBi2Te4 single crystals is probed using a combination of structural and physical properties measurements, together with density functional theory (DFT) calculations. The structural study shows distorted Ge coordination polyhedra, mainly of the Ge octahedra. This has a major impact on the band structure, resulting in bulk metallic behavior of GeBi2Te4, as indicated by DFT calculations. Such calculations place GeBi2Te4 in a class of a few known nontrivial topological metals, and explains why an observed Dirac point lies below the Fermi energy at about -0.12 eV. A topological picture of GeBi2Te4 is confirmed by the observation of surface state modulations by scanning tunneling microscopy.

Crystal growth, structure, and physical properties of LnCu2(Al,Si)5 (Ln = La and Ce).

LnCu(2)(Al,Si)(5) (Ln = La and Ce) were synthesized and characterized. These compounds adopt the SrAu(2)Ga(5) structure type and crystallize in the tetragonal space group P4/mmm with unit cell dimensions of a ≈ 4.2 Å and c ≈ 7.9 Å. Herein, we report the structure as obtained from single crystal X-ray diffraction. Additionally, we report the magnetic susceptibility, magnetization, resistivity, and specific heat capacity data obtained for polycrystalline samples of LnCu(2)(Al,Si)(5) (Ln = La and Ce).