Creation of New memory devices with functional harmonized artificial lattices and elucidation of phase transition

创建具有功能协调的人工晶格的新型存储器件并阐明相变

• 批准号: 11650323
• 负责人: TABATA Hitoshi
• 金额: $ 2.37万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650323/
• 关键词: ferroelectrics; ferromagnet; artificial lattice; perovskite; laser MBE; memory device; functional materials; structural phase transition

Photo induced ferromagnetism in Spinel-Ferrite (Natural superlattice with "Kagome Lattice")The spin-glass system consists of various metastable states depending on the degree of 'spin freezing '. Accordingly, applying appropriate external fields such as light perturbation to the spin-glass state is able to cause a 'melt' of the frozen spins and accelerate the magnetic relaxation, giving rise to an increase of the magnetization up to a new steady state value. We have demonstrated the high temperature spin glass and photo-induced magnetization in the spinel-type ferrite films.Room temperature spin-glass states have been found in (Mg,Fe) {Mg,Fe,Ti}_2O_4, (Co, Zn)FeO_4 and (Ru. Al) FeO_4 spinel ferrite thin films. Here we have reported that room temperature spin-glass has been achieved by the fine-tuning of spin states through the control of composition, random oxygen deficiencies and the stress induced by the film/substrate lattice mismatch in hetero-epitaxial films. All of which give rise to effects that enhance the exchange interaction of spins in the ferrite films. We have demonstrated the change of magnetic state by means of light-irradiation from spin-glass to a ferri-magnet over a wide range of temperatures up to 300 K. The direct photo-excitation of spins with photon energy around 2.0 eV, which corresponds to the spin excitation energy for Fe ions, is the most effective for realizing photo-induced magnetization. Therefore, we can demonstrate that the photo induced ferromagnetism in Spinel-Ferrite (Natural superlattice with "Kagome Lattice").

尖晶石-铁氧体（具有“可果美晶格”的天然超晶格）中的光致铁磁性自旋玻璃系统由取决于“自旋冻结”程度的各种亚稳态组成。因此，将适当的外部场（例如光扰动）施加到自旋玻璃态能够引起冻结自旋的“熔化”并加速磁弛豫，从而引起磁化强度增加到新的稳态值。在（Mg，Fe）{Mg，Fe，Ti}_2O_4，（Co，Zn）FeO_4和（Ru）中发现了室温自旋玻璃态。Al）FeO_4尖晶石铁氧体薄膜。在这里，我们已经报道，室温自旋玻璃已经实现了微调的自旋状态，通过控制成分，随机氧缺陷和应力引起的薄膜/衬底晶格失配异质外延膜。所有这些都产生了增强铁氧体薄膜中自旋交换相互作用的效应。我们在300 K以下的温度范围内，用光照射的方法，证明了从自旋玻璃到亚铁磁体的磁态变化。光子能量约为2.0 eV的自旋的直接光激发（对应于Fe离子的自旋激发能量）对于实现光诱导磁化是最有效的。因此，我们可以证明尖晶石-铁氧体（具有“Kagome晶格”的天然超晶格）中的光致铁磁性。

项目成果

M.Joseph: "Fabrication of the low-resistive p-type ZnO by codoping method"Physica B. 302-303. 140-148 (2001)

M.Joseph：“通过共掺杂方法制造低阻 p 型 ZnO”Physica B. 302-303。

L.T.Cai: "Probing electrical properties of oriented DNA by conducting atomic force microscopy"Nanotechnology. 12. 211-216 (2001)

L.T.Cai：“通过原子力显微镜探测定向 DNA 的电特性”纳米技术。

E.Rokuta: "Effects of an ultrathin silicon oxynitride buffer layer on electrical properities of ferroelectric Bi_4Ti_3O_<12> thin films on p-Si(100) surfaces"Appl. Phys. Lett.. 79(3). 403-405 (2001)

E.Rokuta：“超薄氮氧化硅缓冲层对 p-Si(100) 表面铁电 Bi_4Ti_3O_<12> 薄膜电性能的影响”Appl。

Y.Muraoka: "Photocontrol of spin-glass state in Mg_<1.5>FeTi_<0.5>O_4 spinel ferrite films"Appl. Phys. Lett.. 76(9). 1179-1181 (2000)

Y.Muraoka：“Mg_<1.5>FeTi_<0.5>O_4尖晶石铁氧体薄膜中自旋玻璃态的光控制”

K.Ueda: "Atomic arrangement and magnetic properties of LaFeO_3-LaMnO_3 artificial suprlattices"Phys. Rev. B. 60. R12561-R12564 (1999)

K.Ueda：“LaFeO_3-LaMnO_3人工晶格的原子排列和磁性能”Phys。