Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

Commensurate Itinerant Antiferromagnetism in BaFe2As2: 75As-NMR Studies on a Self-Flux Grown Single Crystal

Abstract: We report results of 75As nuclear magnetic resonance (NMR) experiments on a self-flux grown single crystal of BaFe2As2. A first-order antiferromagnetic (AF) transition near 135 K was detected by the splitting of NMR lines, which is accompanied by simultaneous structural transition as evidenced by a sudden large change of the electric field gradient tensor at the As site. The NMR results lead almost uniquely to the stripe spin structure in the AF phase. The data of spin-lattice relaxation rate indicate development of anisotropic spin fluctuations of the stripe-type with decreasing temperature in the paramagnetic phase.

Temperature dependence of Raman scattering in single crystal GaN films

Abstract: Micro-Raman scattering from single crystal GaN films, both free-standing and attached to Al2O3 substrates, was performed over the temperature range from 78 to 800 K. These measurements reveal that the Raman phonon frequency decreases and the linewidth broadens with increasing temperature. This temperature dependence is well described by an empirical relationship which has proved to be effective for other semiconductors. The experiments also demonstrate that the strain from Al2O3 substrates compresses the epitaxial GaN in the c-axis direction.

Growth, characterization and properties of relaxor ferroelectric PMN-PT single crystals

Abstract: The present paper reviews the recent progress of studies on growth, characterization and properties of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals in Shanghai Institute of Ceramics. Their chemical compositions were selected near the rhombohedral-tetragonal morphotropic phase boundary, more favorable in the rhombohedral phase. The dominant method used for growing the single crystals was the modified Bridgman technique, by which the single crystal boules with the size larger than 25mm diameter and 50 mm long were grown. Different orientation thin plates with thickness less than 1mm were cut from the boules and their domain structures, morphology and properties were characterized. Their phase transition were discussed as well.

Structural and magnetic properties and tunnel magnetoresistance for Co2(Cr,Fe)Al and Co2FeSi full-Heusler alloys

Abstract: We have investigated the structure and magnetization of Co2(Cr1−xFex)Al (0 ≤ x ≤ 1) and Co2FeSi full-Heusler alloy films deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultra-high vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). Magnetic tunnel junctions with a full-Huesler alloy electrode were fabricated with a stacking structure of Co2YZ (20 nm)/Al (1.2 nm)-oxide/Co75Fe25 (3 nm)/IrMn (15 nm)/Ta (60 nm) and microfabricated using electron beam lithography and Ar ion etching with a 102 µm2 junction area, where Co2YZ stands for Co2(Cr1−xFex)Al or Co2FeSi. The tunnel barriers were formed by the deposition of 1.2 nm Al, followed by plasma oxidization in the chamber. The x-ray diffraction revealed the A2 or B2 structure depending on heat treatment conditions and the substrate, but not L21 structure for the Co2(Cr1−xFex)Al (0 ≤ x ≤ 1) films. The L21 structure, however, was obtained for the Co2FeSi films when deposited on a MgO (001) substrate at elevated temperatures above 473 K. The maximum tunnelling magnetoresistance (TMR) was obtained with 52% at RT and 83% at 5 K for a junction using a Co2(Cr0.4Fe0.6)Al electrode. While the junction using a Co2FeSi electrode with the L21 structure exhibited the TMR of 41% at RT and 60% at 5 K, which may be improved by using a buffer layer for reducing the lattice misfit between the Co2FeSi and MgO (001) substrate.