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Growth And Characterization Of The Perovskite RFeO3 Single Crystal

Posted on:2018-04-16Degree:MasterType:Thesis
Country:ChinaCandidate:T XieFull Text:PDF
GTID:2321330518490712Subject:Material Chemical Engineering
Abstract/Summary:PDF Full Text Request
Recently, rare earth orthoferrites RFeO3?R=rare earth?, with perovskite structure, have gained considerable interest. It shows great application potential in many optical devices, such as fast magneto-optic switch, magneto optical sensors, because it possesses spin reorientation transition, excellent magneto-optic and fast response. Due to their high melting point ?1700??and special melting characteristics, many difficulties are encountered in growth of high quality RFeO3 single crystal. The doping and substituting with different types of element are an effective way to regulate and control the properties of the perovskite structure materials.In this paper, single crystals RFeO3 have been grown by the optical floating zone. The growth parameters have been optimized, such as temperature, rotation, atomosphere, and gas flow. Finally, high quality YFe0.6Mn0.4O3, YFe0.8Mn0.2O3 and Sm0.5Pr0.5FeO3 single crystal were successfully grown by optical floating zone method. Single crystal wafers, along a , b,c direction, have been obtained by the X-ray diffraction, and the Laue orientation method. On this basis, their magnetic properties, thermal properties and optomagnetic properties have been systematically studied.Spin reorientation indicates the sophiscated magnetic exchange and competition within the system. Pure YFeO3 does not exhibit spin reorientation, however, upon Mn substitution at the Fe site, a spin-reorientation transition occurs where the spin configuration changes from ?4 to ?1. The easy magnetic axis changes from the a-axis to the b-axis in the ab plane in this process.The spin reorientation for YFe0.8Mn0.2O3 crystal and YFe0.6Mn0.4O3 crystal occur in the temperature region 236K-243K and 316K-322K, respectively. The temperature of spin-reorientation increases with increasing Mn3+. Since the anisotropy energy of Mn3+ is larger than that of Fe3+ at low temperature, the spin moment of Fe3+ will be aligned to the direction of that of Mn3+.The spin-reorientation transition of Sm0.5Pr0.5FeO3 single crystal occurs at 180K-220K where the spin configuration changes from ?4 to ?2. Simultaneously, compensation point and magnetic sudden reverse point, Tcomp and Tssw, were observed Sm0.5Pr0.5FeO3 single crystal along a axis. The compensation point was observed when the magnetic moment of rare earth ions is equal to that of iron ions, with opposite directions. When the magnetic moment of rare earth ions and the weak magnetic moment of iron ions reverse simultaneously, the magnetic sudden reverse point was observed.The antiferromagnetic resonance and ferromagnetic resonance of Sm0.5Pr0.5FeO3 single crystal were studied using Terahertz time-domain spectroscopy ?THz-TDS?, which demonstrates that the antiferromagnetic resonance and ferromagnetic resonance can be excited when the magnetic-field component ?HTHz? of THz pulse were parallel and vertical to ferromagnetic vector ?F? of RFeO3, respectively. The spin reorientation temperature range of Sm0.5Pr0.5FeO3 single crystal was obtained by researching the temperature dependence of the resonant amplitude and frequency, which indicates that the terahertz time-domain spectroscopy is a kind of effective method to explore the spin reorientation transition in rare earth orthoferrites RFeO3.
Keywords/Search Tags:Optical floating zone method, Crystal growth, Magnetic properties, Rare earth orthoferrite
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