CaMn1-xWxO3(0.05≤x≤0.20)体系电荷有序的建立与消失

通过对样品磁化强度-温度（M-T）曲线、磁化强度-磁场强度（M-H）曲线、电阻率-温度（ρ-T）曲线及部分样品ESR谱的测量，研究了Mn位w掺杂对Cabin1-x，WxO3（x=0．05，0．07，0．10，0．12，0．14，0．16，0．20）体系磁结构的影响。结果表明，随着W掺杂量的增加，体系磁结构发生了复杂的变化过程。当掺杂量x≤0．07时，体系为铁磁（FM），反铁磁（AFM）和顺磁（PM）态的共存，随掺杂量增加，FM态减弱，AFM态增强；当x=0．10，0．12时，体系建立电荷有序（charge ordering，CO）态，AFM／CO态共存于相变温度以下，且电荷有序温度TCO随掺杂量增加而增加；当x≥0．14时，体系电荷有序（CO）态减弱并消失。     

Dy和Sm部分替代La对La0.7Sr0.3MnO3磁电行为的影响

通过对La0.7-xTxSr0．3MnO3(T=Dy，Sm)系列样品的红外透射谱，激光拉曼谱，M-T曲线和ρ-T曲线的测量，研究了该样品的磁电行为。结果发现，随着掺入量的增加，样品的顺磁-铁磁相变温度逐渐降低，磁结构从顺磁向自旋团簇玻璃态、反铁磁状态转变，样品的磁电阻迅速增加。有趣的是在较低温度下，Dy掺杂M-T曲线出现比较奇特的尖峰，而Sm掺杂M-T曲线比较变化较平坦。对Dy，Sm掺杂的作用可以用晶格效应和额外磁性的竞争来解释。     

钙钛矿锰氧化物Y0.5Ca0.5Mn0.8Fe0.2O3的电子顺磁共振研究

用固相反应法制备了Y0．5Ca0．5Mn0．8Fe0．2O3多晶陶瓷材料，借助电子顺磁共振技术对多晶样品在150—300K温度范围内的顺磁共振行为进行了研究。结果表明样品的顺磁共振线宽△Hpp和g因子的值随着温度的降低是增加的。线宽的增加是由于随着温度的降低，样品进入一个长程的反铁磁态，体系的铁磁关联增强导致的。g因子随温度的降低而增加表明体系的轨道有序是逐渐增强的。     

在La0.67Sr0.33MnO3中保持Mn3+:Mn4+=2:1的镁掺杂效应

通过测量样品的M-T曲线、M-H曲线、ESR曲线、红外光谱、拉曼光谱、ρ—T曲线和MR-T曲线，研究了双掺杂La0.67 1.33xSr0.33-1.33xMn1-xMgO3(0．00≤x≤0．25)体系的磁电性质和输运行为.对x=0．10和0．15，在温度高于Tc^onset时出现相分离；对x=0．20和0．25，在低温区出现了反铁磁(AFM)行为，x=0．05的ρ-T关系存在金属-绝缘体(MI)转变；x≥0.15的所有样品在测量温区内显示绝缘体行为：这些奇异现象用M-H关系、ESR曲线和拉曼光谱给予了很好的解释.     

钙钛矿钴氧化物La_(0.5-x)Nd_xSr_(0.5)CoO_3(x=0,0.1,0.15)的磁性

采用传统的固相反应法制备了La_(0.5-x)Nd_xSr_(0.5)CoO_3(x=0,0.1,0.15)多晶样品,并通过磁化强度与温度的变化曲线(M-T曲线)和磁化强度与外场的变化曲线(M-H曲线)对其磁性进行了研究。研究结果表明,随着温度的降低三个样品的磁性都先后经历了顺磁、铁磁和反铁磁转变。掺杂量x的增加使得系统的居里外斯温度逐步上升(θ_(x=0)≈215 K;θ_(x=0.1)≈226 K;θ_(x=0.15)≈242 K),这表明Nd~(3+)掺杂使系统内部的铁磁耦合增强。通过对磁化率倒数与温度的变化曲线的拟合,发现三个样品都出现了向上背离居里外斯定律的现象,这种背离是由于系统内部反铁磁相互竞争所致。因此,三个样品均不具有类Griffiths相。另外,通过对高温部分的实验测量与理论计算发现,Co~(4+)的自旋态随着掺杂量x的增加逐渐由低自旋态向中间自旋态过渡。     

La1-xNaxMnO3的磁电性质研究

采用固相反应法制备了La1-xNaxMnO3(x=0.05,0.15,0.33)多晶样品。通过测量XRD(X射线衍射)谱、R-T(电阻-温度)曲线、M-T(磁化强度-温度)曲线和ESR(电子自旋共振)曲线,研究了La位Na+离子替代对体系的电性和磁性的影响。实验结果表明:体系伴随绝缘体-金属相变出现顺磁-铁磁相变,随着La位Na+离子替代量的增加,样品的电阻值先减小后增大,磁化强度先增大后减小;随着La位Na+离子替代量的增加,居里温度单调升高;居里温度附近温区,顺磁相中存在着铁磁团簇,铁磁相中也存在顺磁成分,即出现了磁相分离;少量的Na+离子替代(x=0.05)样品,反铁磁与铁磁相共存,低温下表现为自旋倾斜玻璃态特征,较高Na+离子替代样品的自旋倾斜玻璃态遭到破坏。体系磁电性质的变化来源于Na+离子替代引起的晶体晶格结构的变化、容忍因子t的变化和Mn3+/Mn4+离子比值的变化。     

钙钛矿锰氧化物Nd_(1.2-x)Tb_xSr_(1.8)Mn_2O_7(x=0,0.10,0.15)的类Griffiths相研究

采用固相反应法制备了Nd_(1.2-x)Tb_xSr_(1.8)Mn_2O_7(x=0,0.10,0.15)系列多晶样品,通过样品的XRD谱线,磁化强度随温度、外加磁场的变化曲线(M-T、M-H)等研究样品的晶体结构和磁性。研究结果表明,随掺杂量的增加,样品的结构没有发生明显变化,均为单相的Sr_3Ti_2O_7型四方结构,空间群为I4/mmm。在测量温度范围内,随温度的降低,三个样品分别先后经历了顺磁态、铁磁-顺磁共存态和反铁磁-铁磁共存态的转变。三样品体系中均存在类Griffiths相,在类Griffiths相温度(T_G≈275 K)以上,样品处于顺磁态;在类Griffiths相温区(θT275 K,其中θ为居里温度)范围内,样品处于铁磁-顺磁共存态;在奈尔温度(T_N)以下,样品铁磁性减弱,反铁磁性增强,铁磁和反铁磁性相互竞争导致类自旋玻璃行为出现。此外Tb元素的掺杂对系统中类Griffiths相温度基本没有影响,但对类Griffiths相温区有一定影响。     

钙钛矿锰氧化物La_(1.1)Dy_(0.1)Sr_(1.8)Mn_2O_7样品的磁性研究

采用传统固相反应法制备La1.1Dy0.1Sr1.8Mn2O7多晶样品,并通过测量样品的磁化强度随温度变化曲线(M-T)以及磁化强度随外加磁场的变化曲线(M-H)对样品的磁性进行了研究。结果表明,在整个温度测量范围内,随温度的降低,样品的磁性发生了多次转变,在类Griffiths相温度(TG≈350 K)以上,样品处于纯顺磁态;在三维铁磁有序温度T3D(≈187 K)至TG温度范围内,样品处于铁磁-顺磁共存态;在奈尔温度TN(≈165 K)至T3D温度范围内,样品的铁磁性随着温度的降低逐渐增强;在TN温度以下,样品的反铁磁性增强而铁磁性减弱,表现出了反铁磁和铁磁相互竞争的现象。另外,通过居里外斯拟合以及Griffiths相模型拟合,发现样品在TG以下存在类Griffiths相。     

双层钙钛矿锰氧化物Nd_(1.15)Tb_(0.05)Sr_(1.8)Mn_2O_7的磁性和电性研究

采用传统固相反应法制备双层锰氧化物Nd1.15Tb0.05Sr1.8Mn2O7多晶样品,通过测量样品的X射线衍射谱、磁化强度随温度变化曲线(M-T曲线)以及电阻率随温度变化曲线(ρ-T曲线),对其磁性和电输运性质进行了研究。结果表明,样品随温度的升高先后经历了四个磁转变点:奈尔温度点(TN≈50 K)、电荷有序温度点(TCO≈67 K)、居里温度点(TC≈107 K)和类Griffiths温度点(TG≈275 K)。在低温部分样品处于反铁磁-铁磁共存态,表现出了团簇自旋玻璃行为;在TC到TG温度范围内,样品处于铁磁-顺磁共存态,即存在类Griffiths相;在TG温度以上,样品处于纯顺磁态。其电输运性质表明,随温度的升高,样品的磁电阻率降低,没有发生金属-绝缘转变。通过对115 K~300 K温度范围内的ρ-T曲线拟合发现,样品在高温部分基本遵循三维变程跳跃的导电方式。     

在La_(0.67)Sr_(0.33)MnO_3中保持Mn~(3+)∶Mn~(4+)=2∶1的镁掺杂效应

通过测量样品的M T曲线、M H曲线、ESR曲线、红外光谱、拉曼光谱、ρ -T曲线和MR T曲线 ,研究了双掺杂La0 .6 7+ 1 .33xSr0 .33- 1 .33xMn1 -xMgxO3(0.0 0≤x≤ 0 .2 5 )体系的磁电性质和输运行为。对x =0 .10和 0 .15 ,在温度高于TConset时出现相分离 ;对x =0 .2 0和 0 .2 5 ,在低温区出现了反铁磁 (AFM )行为。x =0 .0 5的 ρ-T关系存在金属 绝缘体 (MI)转变 ;x≥ 0 .15的所有样品在测量温区内显示绝缘体行为。这些奇异现象用M H关系、ESR曲线和拉曼光谱给予了很好的解释     

磁电阻材料的发展及应用

主要介绍了现阶段在磁电阻薄膜材料方面取得的新进展,对其基本原理进行了论述,以及对该薄膜材料特别是CMR和EMR材料的应用范围和应用前景进行了分析。     

浅谈铝电解生产中阳极效应的危害性

本文分析了铝电解生产中阳极效应的危害性。指出随着科技的不断发展，在生产中，只要槽况正常，就无需利用效应。“零效应”管理是铝电解生产今后发展的方向。     

Interactions Among the Imagination, Expertise Reversal, and Element Interactivity Effects.

Interactions among the imagination, expertise reversal, and element interactivity effects were investigated in 2 experiments. In Experiment 1, less knowledgeable primary school students learning to use a bus timetable produced better performance under study than imagination conditions, but an increase in their experience reversed the result, producing the imagination effect. Experiment 2, in which students were taught to use a temperature line graph, replicated these results and demonstrated that the effects were more likely to be obtained using complex material. It was concluded that learners can engage more successfully in imagination procedures when learning has proceeded sufficiently to permit the information to be processed in working memory and that working memory limitations are of little consequence except when dealing with complex information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

纳米材料与纳米技术的研究方向及应用前景

纳米材料具有独特的表面效应、体积效应和量尺寸效应，使得材料的性能发生突变，纳米材料及采用纳米材料的纳米技术也因此成为材料科学与工程研究及应用最重要的发展方向之一。对国内外纳米材料及纳米技术的研究现状及其广阔的应用前景进行了综述，同时对纳米材料研制开发中的重要基础理论问题进行了探讨。     

浅谈铝电解的阳极效应

通过对阳极效应的发生机理以及效应的利和弊的分析和探讨,不断总结实践经验,找出降低阳极效应系数的有力措施,努力反效应消灭在萌芽状态。     

Lattice Effects in La-Sm-Ca-Mn-O

The doping effects of Sm in La0.67Ca0.33MnO3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal-insulator for the materials decreases monotonically, the cor-responding peak resistance increases rapidly, the Curie temperature decreases monotonically, and the magneto-resistance ratio increases quickly. The effects of Sm doping can be explained in terms of lattice effects.     

Effect size measures for mediation models: Quantitative strategies for communicating indirect effects.

The statistical analysis of mediation effects has become an indispensable tool for helping scientists investigate processes thought to be causal. Yet, in spite of many recent advances in the estimation and testing of mediation effects, little attention has been given to methods for communicating effect size and the practical importance of those effect sizes. Our goals in this article are to (a) outline some general desiderata for effect size measures, (b) describe current methods of expressing effect size and practical importance for mediation, (c) use the desiderata to evaluate these methods, and (d) develop new methods to communicate effect size in the context of mediation analysis. The first new effect size index we describe is a residual-based index that quantifies the amount of variance explained in both the mediator and the outcome. The second new effect size index quantifies the indirect effect as the proportion of the maximum possible indirect effect that could have been obtained, given the scales of the variables involved. We supplement our discussion by offering easy-to-use R tools for the numerical and visual communication of effect size for mediation effects. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Learning from feedback: Spacing and the delay–retention effect.

Most modern research on the effects of feedback during learning has assumed that feedback is an error correction mechanism. Recent studies of feedback-timing effects have suggested that feedback might also strengthen initially correct responses. In an experiment involving cued recall of trivia facts, we directly tested several theories of feedback-timing effects and also examined the effects of restudy and retest trials following immediate and delayed feedback. Results were not consistent with theories assuming that the only function of feedback is to correct initial errors but instead supported a theoretical account assuming that delaying feedback strengthens initially correct responses due to the spacing of encoding opportunities: Delaying feedback increased the probability of correct response perseveration on the final retention test but had minimal effects on error correction or error perseveration probabilities. In a 2nd experiment, the effects of varying the lags between study, test, and feedback trials during learning provided further support for the spacing hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple systems for cognitive control: Evidence from a hybrid prime-Simon task.

Cognitive control resolves conflicts between appropriate and inappropriate response tendencies. Is this achieved by a unitary all-purpose conflict control system, or do independent subsystems deal with different aspects of conflicting information? In a fully factorial hybrid prime-Simon task, participants responded to the identity of targets displayed at different nominally irrelevant screen locations, preceded by nominally irrelevant, consciously or nonconsciously perceived primes. The response required by the target's identity could match or mismatch (a) the target's location, and (b) the prime's identity, resulting in potential conflict (a) across and (b) within stimulus domains. Conflict effects were investigated within and across trials. Results suggest that (i) nonconsciously perceived information elicits within-trial control, but—unlike consciously perceived information—no across-trial behavioral modulation; (ii) separate subsystems deal with conflicts arising from different stimulus domains; and (iii) occasional apparent interactions between domains reflect a particular difficulty in reactivating a just-discarded response (reactivation aversion effect, RAE). (PsycINFO Database Record (c) 2011 APA, all rights reserved)