Tri-arc Czochralski Research Articles

Absence of Kondo resonance in high-resolution photoemission spectra of monocrystallineFe1−xCoxSi

${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{Si}$ single crystals with different Co concentrations were grown using the tri-arc Czochralski technique. Samples with 0, 5, and $20\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ of Co were studied with photon energies of 21.2 and $40.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ with spectral resolutions as high as $8\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ at the Fermi level. For FeSi, a full gap of $28\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ has been found, which closes with 5% of Co. In the range between 20 and $150\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, energy dependent angle-resolved measurements in the [111] direction were made for FeSi. Through a comparison with theoretical calculations, the states at the Fermi energy can be directly assigned to $\mathrm{Fe}\phantom{\rule{0.2em}{0ex}}3d$ states. No sign of Kondo resonance is found.

Ultraviolet photoemission spectroscopic and magnetic properties of Fe 1− xCo xSi single crystals

We have grown Fe 1− x Co x Si single crystals with different Co concentration using the tri-arc Czochralski technique. Ultraviolet photoemission spectra reveal a sharp valence band maximum shifting towards the Fermi energy with increasing Co concentration. The magnetic characterization has been performed with a commercial SQUID magnetometer. The samples show paramagnetic behavior up to x=0.05 and ferromagnetism for higher Co content. The experimental results are discussed within existing and spd-hybridization models.

Growth and magnetic properties of single crystal Co/sub 2/MnX (X=Si,Ge) Heusler alloys

Half-metallic (HM) ferromagnetic materials have recently drawn intense interests due to their potential use in magnetoelectronic devices. Co-based Heusler alloys of the type CO/sub 2/MnX (X=Si,Ge), predicted to be HM by first principles band structure calculations, are of particular interest since they alone possess Curie temperatures in excess of 900 K. Since the spin polarization (P) is believed to be sensitive to antisite defects that are likely to occur in vapor-quenched thin film synthesis, single crystals of Co/sub 2/MnX (X=Si, Ge) were prepared using the tri-arc Czochralski method. X-ray diffraction, including Laue backscattering, was employed to determine the high crystalline quality of these crystals. SQUID magnetometry measured a magnetic moment per formular unit that is close to the calculated value indicating that these alloys may in fact be HM. However, point contact Andreev reflection, a technique that has reliably measured high P in CrO/sub 2/, measures P values for these crystals of 50-60%, well below their theoretical values. The reduced spin polarization may be due to the effects of crystal symmetry breaking at the surface or the presence of anti-site defects, or that these materials are not truly half-metallic.

A tri-arc system for growing high-purity crystals of metallic materials

A tri-arc Czochralski crystal growth system, for preparing high-purity crystals of metallic materials, is described. To improve the environmental cleanliness within the chamber beyond that found in conventional tri-arc systems, the equipment is built to ultra-high-vacuum standards (although actual operation in vacuum is not possible) so that leaks into the system and degassing of contaminating gases from the chamber walls during growth are minimized. Crystal growths of the intermetallic compounds TiAl and HoCo 2 are illustrated.

Tri-arc Czochralski growth of single crystal molybdenum disilicide

A tri-arc Czochralski apparatus and procedure used to grow MoSi 2 crystals is detailed. Problems with Si evaporation and compositional banding are described. Growth orientations and other microstructural features of the crystals are discussed.

Single Crystal Growth and Electrical Properties of CeRh2and CeIr2

We have grown single crystals of CeRh 2 and CeIr 2 by a tri-arc Czochralski pulling method. Electrical properties including the de Haas-van Alphen effect are presented.

Single crystal growth and electrical properties of CeRh2 and CeIr2

Abstract We have succeeded in growing single crystals of CeRh 2 and CeIr 2 by a tri-arc Czochralski pulling method. Electrical properties including the de Haas-van Alphen effect are presented.

Crystal growth and characterization of UxCe1− xRu2Si2 pseudo-ternary system

Single crystals of the pseudo-ternary intermetallic compounds U x Ce 1− x Ru 2 Si 2 ( x ≤ 0.15 and x ≥ 0.95) have been grown by a modified tri-arc Czochralski method and characterized by means of X-ray, electron-probe microanalysis, electrical-resistivity and heat-capacity measurements. The electron-probe microanalysis revealed oscillations in the U/Ce ratio and formation of “stripes” which are perpendicular to the crystal growth direction. A small value of the linear specific-heat coefficient λ = 33 mJ/ mol· K 2 x = 0.99) indicates suppression of the heavy-fermion behaviour by alloying of URu 2Si 2 with Ce. On the other hand, the coefficient λ = 260 and 290 mJ/ mol· K 2 ( x = 0.10, 0.05) is quite large, confirming the heavy Fermi-liquid nature of the Ce-rich compounds.

High field and temperature dependent magnetisation measurements on some RE/sub 2/Co/sub 17/ single crystals

Single crystals of Pr/sub 2/CO/sub 17/ and Nd/sub 2/Co/sub 17/ have been grown using a tri-arc Czochralski method. High-field magnetization measurements up to 35 T have been performed on Pr/sub 2/Co/sub 17/ and Nd/sub 2/Co/sub 17/ at 4.2 K. The experimental curves show very large anisotropy; for fields along the c axis in Pr/sub 2/Co/sub 17/ and along the a axis in Nd/sub 2/Co/sub 17/ the magnetization does not reach the saturation value within this field range. Furthermore, the hard axis shows in both compounds a nonzero spontaneous magnetization indicating a cone structure with cone angles of about 26 degrees and 7 degrees for Pr/sub 2/Co/sub 17/ and Nd/sub 2/Co/sub 17/, respectively. Low-field (up to 6 T) temperature-dependent magnetization measurements (4.2-300 K) show that in both compounds the cone angle remains visible up to 300 K, but for Pr/sub 2/Co/sub 17/ the cone angle is drastically reduced above 150 K. These two RE/sub 2/TM/sub 17/ compounds (RE stands for a rare-earth metal and TM stands for a transition metal) with a cone structure are compared with other RE-TM compounds with a cone structure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The crystal growth of uranium tetraboride UB 4 from the melt

A bulk single crystal of UB 4 (tetragonal ThB 4-type of structure, melting temperature of 2500°C, approximately) with dimensions of 5 mm diameter and 40 mm length has been grown by a modified tri-arc Czochralski method in a continuously Ti-gettered atmosphere. The lattice parameters measured on the as-grown bulk single crystal are: a = 7.0764 Å and c = 3.9811 Å. The experimentally determined density of 9.46 g/cm 3 coincides within the experimental error with the density value of 9.38 g/cm 3 calculated from the lattice parameter data. The magnetic susceptibility measured along the a- and c-axis reveals a strong anisotropy. No evidence for superconductivity was found down to 0.3 K. In addition, specific heat data on a polycrystalline UB 4 sample are given.

Growth of crystals of V 2O 3 and (V 1−xCr x) 2O 3 by the tri-arc czochralski method

(V 1−xCr x) 2O 3 for x = 0.0 to 0.018 crystals were grown by the tri-arc Czochralski technique. They were of good chemical purity and were found to have negligible solubility. For 0.010 ≲ x ≲ 0.015 there is evidence for the coexistence of both the paramagnetic insulating and the paramagnetic metallic phases.