Single crystals of a spin-1/2 Heisenberg alternating chain compound, high pressure phase of (VO)2P2O7 , was grown by slowly cooling the melt at 3 GPa. Powder XRD study at high pressure using synchrotron radiation was performed in advance to observe the formation and the melting of this compound

Azuma, Masaki

Saito, Takashi

Takano, Mikio

Kyoto University Research Information Repository

Title Single Crystal Growth at High Pressure (SOLID STATECHEMISTRY-Multicomponent Materials)Author(s)Azuma, Masaki; Saito, Takashi; Takano, MikioCitationICR annual report (2000), 6: 20-21Issue Date2000-03URL http://hdl.handle.net/2433/65239RightType ArticleTextversionpublisherKyoto UniversityICR Annual Report, Vol. 6, 199920Single Crystal Growth at High PressureSingle crystals of a spin-1/2 Heisenberg alternating chain compound, high pressure phase of (VO)2P2O7, was grown by slowly cooling the melt at 3 GPa.  Powder XRD study at high pressure using synchrotronradiation was performed in advance to observe the formation and the melting of this compound.Keywords:   High pressure synthesis/ Synchrotron radiation XRD/ Single crystal growthMasaki Azuma, Takashi Saito and Mikio TakanoSOLID STATE CHEMISTRY  — Multicomponent Materials —Scope of researchNovel 3d transition-metal oxides showing exotic electrical and magnetic properties are being searched for using differentsynthesizing techniques like high pressure syntesis (5 GPa and 1000℃, typically) and epitaxial film growth. Recent topics are:• High Tc superconductivity.• Low-dimensional spin systems like ladders showing dramatic quantum effects.• Oxides of late 3d transition metals like SrFeO3 with strong oxygen-hole character.ProfTAKANO, Mikio(D Sc)Assoc ProfTERASHIMA, Takahito(D Sc)InstrAZUMA, Masaki(D Sc)Students:YAMADA, Takahiro (DC)FURUBAYASHI, Yutaka (DC)HAYASHI, Naoaki (DC)SAITO, Takashi (DC)ISHIWATA, Shintaro (MC)ODAKA, Tomoori (MC)TERASHIMA, Takashi (MC)MASUNO, Atsunobu (MC)Research Fellow:KAWASAKI, ShujiHigh pressure synthesis is a powerful technique tosearch for new materials. Various quantum spincompounds including high Tc superconductors andquantum spin ladders [1] have been found using thismethod in a past decade.  However, the limitation of thesample space and the difficulty in the direct observationof  high pressure reactions made it difficult to grow singlecrystals of such compounds.The high pressure phase of (VO)2P2O7 (HP-VOPO) isa spin-1/2 Heisenberg alternating chain compound with aspin gap stabilized at 2GPa and 700 °C[2]. We havesucceeded in growing single crystals of this compoundby slowly cooling the melt at 3GPa [3].  High pressurepowder X-ray diffraction (XRD) was performed using acubic-anvil type high pressure apparatus (SMAP 1800)installed at BT14B1 of SPring-8, Japan SynchrotronRadiation Research Institute, to determine the meltingtemperature.  White beam X-ray from the synchrotronradiation was irradiated to the sample in a platinum capsulethrough the high pressure cell and was detected by thesolid state detector fixed at 2θ = 4°.  Figure 1 shows theXRD patterns taken at 3GPa and at various temperatures.When the pressure was applied, the peak shifted to thehigh energy direction indicating a shrinkage of the lattice.The peak broadening was due to strains in the particles.The peaks sharpened again with increasing the temperatureand new peaks corresponding to (2 2 1), (1 1 3) and (2 31) reflections of the HP phase appeared at 500°C.  Thisclearly showed that the transition to the HP phase tookplace between 400 and 500°C.  Finally at 1150°C thesample melted and all the peaks disappeared expect forthose of characteristic X-rays of lead.Single crystals were grown by slowly cooing the meltat 3GPa.  About 2 g of the ambient pressure phase samplewas packed in a platinum capsule of 9.6 mm in diameterand 15 mm height and compressed using a cubic anviltype high pressure apparatus.  The sample was first heatedto 1200°C and then cooled to 600°C in 60 h.  Greentransparent crystals of a typical size of 1 mm × 0.5 mm ×0.2 mm were obtained.  A magnified view of obtainedcrystals is shown in Fig. 2.References1. M.  Azuma, Z.  Hiroi, M.  Takano, K.  Ishida and Y.  Kitaoka,Phys.  Rev.  Lett. 73, 3468 (1994).2. M. Azuma, T. Saito, Y. Fujishiro, Z. Hiroi, M. Takano, F.Izumi, T. Kamiyama, T. Ikeda, Y. Narumi and K. Kindo, Phys.Rev. B 60, 10145 (1999).3. T. Saito, M. Azuma, M. Takano, T. Goto, H. Ohta, W. Uthumi,P. Bordet and D. C. Johnston, preprint.ICR Annual Report, Vol. 6, 1999 21Figure 2 Single crystals of HP (VO)2P2O7 grown at 3 GPa.Epitaxial Growth of Fe4+(3d4)-Perovskite Oxides Thin FilmsT. Terashima, N. Hayashi and M. Takano   Perovskite-type oxides containing high valent Fe4+(3d4)are prototypical systems to study electronic propertiesdominated by oxygen-hole character. SrFeO3 (SFO) is abroad band metal down to the lowest temperature. Al-though the electronic state of SFO has attracted much at-tention, detailed transport properties have not been clari-fied due to the difficulty of the preparation of a singlecrystal. The high pressure treatment is required to oxi-dize Fe to Fe4+ state. The epitaxial growth is an alterna-tive way to prepare a metastable substance. We report asuccessful growth of the epitaxial thin films of SFO bythe pulsed laser deposition and subsequent ozone oxida-tion.    The films were grown by the pulsed laser depositionwith KrF eximer laser (λ=248nm). The deposition condi-tions are the following: The substrate temperature was650˚C and the oxygen pressure during the deposition was5 0 0 m T o r r .  T h e  s u b s t r a t e  w a s  L S AT((LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7) (100) which has a good lat-tice matching  with SFO. After the deposition the filmwas cooled with blowing partially ozonized oxygen.    The epitaxial growth  was confirmed by the reflectionhigh-energy electron diffraction measurement. An equi-intensity contour map of X-ray scattering around (203)point for the SFO film is displayed in Fig.1. The narrowpeak widths of the SFO film comparable to those of thesubstrate show good crystallinity of the film. The calcu-lated in-plane and out-of plane lattice spacings are  3.865Åand 3.837Å, respectively, revealing a pseudo tetragonalstructure of the film caused by an elastic strain.    Figure 2 shows the temperature dependence of the re-sistivity for the SFO film. The film exhibited metallic be-havior with much lower resistivity than bulk sample pre-pared by high-pressure synthesis. A change in dR/dT isseen at 100K, which would be correlated to a magneticordering. Measurements of the transport properties, suchas Hall effect and magnetoresistance, of the SFO film arenow in progress.Figure 1 Powder XRD patterns of (VO)2P2O7 taken at 3 GPaand various temperatures.Figure 1. Equi-intensity contour map of X-ray scattering aroundthe    (203) point for the SFO thin film.Figure 2. Temperature dependence of the resistivity for the SFOthin film and bulk.Epitaxial films of SrFeO3 containing high valent Fe4+(3d4) were successfully grown by the pulsed laserablation and subsequent ozone annealing. The film showed good crystallinity and lower resistivity thana bulk sample.Keywords: Fe4+/ Perovskite oxides/ Thin film/ Epitaxial growth/ Laser ablationIntensity /arb. unitEnergy /keV8075706560555045200 024 016224200115032232022031221 013113 222231AP-VOPO1 atm, 27 °C201211123HP-VOPO1 atm, r.t.201Pb Kα1Pb Kα2r.t.200°C400°C500°C700°C900°C1100°C1150°C3 GPa

Single Crystal Growth at High Pressure (SOLID STATE CHEMISTRY-Multicomponent Materials)

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/65239/1/v6-p20.pdf

Single Crystal Growth at High Pressure (SOLID STATE CHEMISTRY-Multicomponent Materials)

Abstract

Similar works

Full text

Available Versions

Kyoto University Research Information Repository