激光能量对反钙钛矿GaCMn_3薄膜结构与物性的影响

本文采用脉冲激光沉积方法在LaAlO3(001)单晶衬底上制备了反钙钛矿GaCMn3薄膜,通过控制制备过程中脉冲激光的能量,研究了不同激光能量条件对GaCMn3薄膜结构与物理性能的影响.分别利用X射线衍射仪、原子力显微镜、超导量子干涉仪和物理性能测试系统,对所制备的薄膜的晶体结构、表面形貌和磁性、电输运性质进行了研究.结果表明,制备的样品均为具有多个晶面取向的反钙钛矿薄膜,且薄膜结构和物性明显随制备激光能量的变化而变化.当激光能量为450mJ时,制备的薄膜多晶面取向性最弱,结晶性和表面形貌最优良.实验所得的薄膜均表现出顺磁-铁磁-反铁磁相转变,然而转变过程比块材较平缓,同时薄膜的电阻率并未表现出块材中的突变特征,我们推测该现象很可能是由衬底的应力及衬底的晶格膨胀对薄膜反常晶格变化的抑制作用造成的.     

Extended phase diagram of La1-xCaxMnO3 by interfacial engineering

The interfacial enhanced ferromagnetism in maganite/ruthenate system is regarded as a promising path to broaden the potential of oxide-based electronic device applications. Here, we systematically studied the physical properties of LaLa_1-xCa_xMnO₃/SrRuO₃ superlattices and compared them with the LaLa_1-xCa_xMnO₃ thin films and bulk compounds. The LaLa_1-xCa_xMnO₃/SrRuO₃ superlattices exhibit significant enhancement of Curie temperature (T_C) beyond the corresponding thin films and bulks. Based on these results, we constructed an extended phase diagram of LaLa_1-xCa_xMnO₃ under interfacial engineering. We considered the interfacial charge transfer and structural proximity effects as the origin of the interface-induced high T_C. The structural characterizations revealed a pronounced increase of B-O-B bond angle, which could be the main driving force for the high T_C in the superlattices. Our work inspires a deeper understanding of the collective effects of interfacial charge transfer and structural proximity on the physical properties of oxide heterostructures.     

La0.67Ca0.33MnO3/NdGaO3(001)薄膜中外延应变诱导的各向异性磁阻效应

本文使用脉冲激光沉积方法在正交的NdGaO3(001)衬底上外延生长了La0.67Cao.33MnO3薄膜.退火后,由于外延应变引起薄膜正交畸变增强,薄膜在低于250K的整个温度区间都出现了铁磁金属态和反铁磁绝缘态的相分离和相竞争.这两相的竞争强烈依赖于磁场相对晶轴的方向,由此导致存在于很宽温度范围内的低场各向异性磁阻...     

采用新型La_(0.07)Sr_(0.93)SnO_3电极制备外延透明BiFe_(0.95)Mn_(0.05)O_3铁电薄膜电容器

本文使用脉冲激光沉积的方法在SrTiO3(STO)单晶衬底上采用一种新型的透明导电氧化物材料La0.07Sr0.93SnO3(LSSO)薄膜作为电极材料制备了BiFe0.95Mn0.05O3(BFMO)铁电薄膜电容器.XRD表征结果证实BF-MO/LSSO/STO外延异质结具有很好的单晶质量.光透过率的测试结果表明在500~2500nm的波长范围内,整个异质结的透光率与单纯STO衬底基片相似.在波长500nm附近BFMO出现吸收边,通过对吸收边进行(hνα)2-hν曲线拟合得到BFMO的直接光学带隙约为2.8eV.利用Pt作为上电极,我们测得了饱和的电滞回线,剩余极化Pr~60μC/cm2.     

Gd掺杂对Bi2Sr2Ca1-xGdxCu2Oy单晶载流子浓度和各向异性电阻率的影响

系统地研究了Gd掺杂对Bi2Sr2Ca1-xGdxCu2Oy单晶超导电性及各向异性电阻率的影响.Tc满足Tc/Tc,max=1-82.6(ax+b)2,并随Gd含量的增加而下降,这是由于Gd掺杂引起载流子浓度减小所导致.在x≥0.19时,ρab(T)在Tc附近有类半导体行为,dρab/dT随Gd含量增大而增大.ρc(T)呈半导体行为,并可用唯象公式ρc(T)=(a/T)exp(Δ/T)+bT+c加以描述.电阻率各向异性ρc/ρab随掺杂浓度增大而增大.     

Gd掺杂对Bi2Sr2Ca1—xGdxCu2Oy单晶载流子浓度和各向异性电阻率？…

系统地研究了Ｇｄ掺杂对Ｂｉ２Ｓｒ２Ｃａ１－ｘＧｄｘＣｕ２Ｏｙ单晶超导电性及各向异性电阻率的影响。Ｔｃ满足Ｔｃ／Ｔｃ,ｍａｘ＝１－８２．６（ａｘ＋ｂ）＾２,并随Ｇｄ含量的增加而下降,这是由于Ｇｄ掺杂引起载流子浓度减小所导致。在ｘ≥０．１９时,ρａｂ（Ｔ）在Ｔｃ随近有类半导体行为,ｄρａｂ／ｄＴ随Ｇｄ含量的增大而增大。ρｃ（Ｔ）呈半导体行为,并可用唯象公式ρｃ（Ｔ）＝（ａ／Ｔ）ｅｘｐ（△／Ｔ）＋ｂＴ＋     

SURFACE PHASE DECOMPOSITION IN Bi2Sr2CaCu2O7-y SINGLE CRYSTALS UNDER NITROGEN IONS IRRADIATION

The influence of irradiation by 30 keV nitrogen ions with a fluence 1×10¹⁸N⁺·cm^-2 on the crystal structure of single crystal Bi₂Sr₂CaCu₂O_7-y was investigated by means of X-ray photoelectron spectroscopy and X-ray diffraction. The irradiation caused a transformation from Bi₂Sr₂CaCu₂O_7-y (2212 phase) to Bi₂Sr₂CuO_5-x (2201 phase). It was observed that. a small amount of metallic bismuth with an average thickness of about 6.3nm appeared after the irradiation. The possible reaction mechanism under nitrogen-ion irradiation was discussed.     

CaIrO3薄膜中的八面体扭转及金属绝缘转变

本文采用激光脉冲沉积(pulsed laser deposition,PLD)方法在NdGaO3(110)(NGO)和(LaAlO_3)_(0.3)(Sr_2AlTaO_6)_(0.7)(001)(LSAT)衬底上生长了厚度变化的钙钛矿结构CaIrO3(CIO)单晶薄膜.在这一体系中,我们观测到了金属绝缘转变现象以及各向异性电输运行为,并且尝试利用应变弛豫调节铱氧八面体绕[100]轴的扭转角度,改变金属绝缘转变温度(TMI).八面体的扭转角度在30nm厚的样品中取得了最大值,同时CIO的TMI取得了最小值.我们推测是八面体的扭转影响了CIO薄膜的带隙宽度,从而造成了TMI的变化以及各向异性电输运行为.     

SURFACE PHASE DECOMPOSITION IN Bi2Sr2CaCu2O7-y SINGLE CRYSTALS UNDER NITROGEN IONS IRRADIATION

The influence of irradiation by 30 keV nitrogen ions with a fluence 1×10¹⁸N⁺·cm^-2 on the crystal structure of single crystal Bi₂Sr₂CaCu₂O_7-y was investigated by means of X-ray photoelectron spectroscopy and X-ray diffraction. The irradiation caused a transformation from Bi₂Sr₂CaCu₂O_7-y (2212 phase) to Bi₂Sr₂CuO_5-x (2201 phase). It was observed that. a small amount of metallic bismuth with an average thickness of about 6.3nm appeared after the irradiation. The possible reaction mechanism under nitrogen-ion irradiation was discussed.     

三个不同温区下影响Bi_2Sr_2CaCu_2O_y单晶抗磁转变宽度因素的研究(英文)

本文研究了三个不同退火温区下（低于４５０℃、４５０～７００℃和高于７００℃）影响Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏｙ单晶抗磁转变宽度的因素．发现普遍被接受的在７００℃以下退火温区的分界线并不明确．ΔＴｃ的变化强烈依赖于退火条件，即使在２５０℃的较低退火温度下，Ｔｃ和ΔＴｃ也可以通过快速淬火而得到显著改善．然而在７００℃以上、不同条件下退火均得到较宽的ΔＴｃ与已有的报道是一致的，这可能是Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏｙ单晶的本征行为．以上结果可以用额外氧的含量和位置、阳离子迁移引起的结构调整来解释．