An Improved Method for Obtaining Single-Phase Sr2MoO4 under Controlled Ultra-low Oxygen Partial Pressure

We investigated a method for obtaining a sintered bulk sample of single-phase Sr2MoO4, which has recently increased in importance due to its similarities to superconducting Sr2RuO4. We discovered that with the aid of Ti2O3 as a p(O2) buffer, high-purity Sr2MoO4 is successfully synthesized in a sealed tube. We confirmed the space group and determined the exact elemental composition of the compound in order to establish its stoichiometry. The guideline for the rational choice of a p(O2)-buffer material is discussed.Comment: 4 pages, 4 figure

Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCo2_2O4_4

Ultrasound velocity measurements of the orbitally-frustrated GeCo$_2$O$_4$ reveal unusual elastic instabilities due to the phonon-spin coupling within the antiferromagnetic phase. Shear moduli exhibit anomalies arising from the coupling to short-range ferromagnetic excitations. Diplike anomalies in the magnetic-field dependence of elastic moduli reveal magnetic-field-induced orbital order-order transitions. These results strongly suggest the presence of geometrical orbital frustration which causes novel orbital phenomena within the antiferromagnetic phase.Comment: 5 pages, 3 figure

Silicon Epitaxial Reactor for Minimal Fab

Cost-effective and mass production of size-controlled wafers becomes one of the future trends for electronic devices. Herein, we design a Minimal Fab system for the growth of half-inch-diameter silicon wafer devices. Different from the conventional chemical vapour deposition (CVD) systems, a new-type of CVD reactor was designed and developed for the Minimal Fab. The minimal CVD reactor has a small reaction chamber for rapid growth processes. It employed (i) a vertical gas flow, (ii) heating modules using concentrated infrared light, (iii) chlorine trifluoride gas for quick reactor cleaning and (iv) optimized epitaxial growth conditions so that the reactor cleaning is not necessary. Reducing the total gas flow rate is an effective way to increase the wafer temperature. The heating process was further assisted by the absorption of infrared light by the precursor trichlorosilane. The slimly designed reflector could help in improving the heating speed

Spin-orbit coupling inactivity of Co2+^{2+} ion in geometrically frustrated magnet GeCo2_2O4_4

We report single-crystal neutron diffraction studies on a spinel antiferromagnet GeCo$_2$O$_4$, which exhibits magnetic order with a trigonal propagation vector and tetragonal lattice expansion ($c/a\simeq1.001$) below $T_{\rm N}=21$ K. For this inconsistency between spin and lattice in symmetry, magnetic Bragg reflections with a tetragonal propagation vector were discovered below $T_{\rm N}$. We discuss spin and orbital states of Co$^{2+}$ ion underlying the new magnetic component.Comment: 3 pages 2 figures, submitted to ICFCM proceeding (Journal of Physics: Conference Series, 2011