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Electron paramagnetic resonance in magnetic semiconductor epitaxial layers and superlattices.

机译：磁性半导体外延层和超晶格中的电子顺磁共振。

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摘要

This thesis presents results of research on the paramagnetic resonance absorption of diluted magnetic semiconductors (DMSs) in layered form, i.e. compounds of the form {dollar}rm Asp{lcub}II{rcub}sb{lcub}1-x{rcub}Msb{lcub}x{rcub}Bsp{lcub}VI{rcub}{dollar}, where {dollar}rm Asp{lcub}II{rcub}{dollar} and {dollar}rm Bsp{lcub}VI{rcub}{dollar} are group II and VI elements, and M is a magnetic transition metal ion.; We have explored the possibility of using electron paramagnetic resonance (EPR) of Mn{dollar}sp{lcub}++{rcub}{dollar} for measuring uniaxial strain in II-VI superlattices. This work is motivated by the fact that the EPR of Mn{dollar}sp{lcub}++{rcub}{dollar} is strongly affected by crystalline fields. Changes in a crystalline field which arise from strain are thus automatically expected to have a profound effect on the EPR spectrum.; The EPR has exhibited a variety of new phenomena. We have observed giant crystal field splittings of Mn{dollar}sp{lcub}++{rcub}{dollar} in ZnTe/MnTe and CdTe/MnTe superlattices{dollar}sp{lcub}1,2{rcub}{dollar}. The EPR spectra are ascribed to isolated Mn{dollar}sp{lcub}++{rcub}{dollar} ions diffused into the ZnTe or CdTe layers from the MnTe layers. Furthermore, we have shown that these shifts can be used as a strain gauge in such superlattices, yielding the magnitude, sign, and uniformity of strain. Comparisons of results using neutron scattering agree well with results from EPR.; We have also measured the EPR of a series of {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Se{dollar} epilayer systems. The room temperature EPR linewidth versus x result in a simply varying quadratic relationship which offers an easy and precise method of determining the Mn{dollar}sp{lcub}++{rcub}{dollar} concentration in epilayers for {dollar}x>0.05{dollar}. The temperature dependence of the EPR linewidth was analyzed in terms of exchange-narrowing theory and the Dzyaloshinski-Moriya (D-M) exchange constant D{dollar}sb1{dollar} determined, with an average value of D{dollar}sb1=0.30{dollar} K, in reasonable agreement with Larson's calculated value.; Finally, we have investigated spin-spin interactions in very dilute systems by studying the {dollar}-{lcub}1over2{rcub}to{lcub}1over2{rcub}{dollar} transitions in a ZnTe/MnTe and CdTe/MnTe strained superlattice. The temperature dependence of the EPR linewidth has characteristics similar to those observed in high-x DMS systems (except in magnitude): a dramatic broadening with decreasing temperature. Analysis of the linewidths in terms of exchange-narrowing theory yields the surprising result that the D-M interaction is still the dominant magnetic interaction, even at very dilute Mn{dollar}sp{lcub}++{rcub}{dollar} concentrations, where the D-M interaction is expected to be small.
机译：本文提出了分层形式的稀磁半导体（DMS）的顺磁共振吸收的研究结果，即形式为{dol} rm Asp {lcub} II {rcub} sb {lcub} 1-x {rcub} Msb形式的化合物{lcub} x {rcub} Bsp {lcub} VI {rcub} {dollar}，其中{dollar} rm Asp {lcub} II {rcub} {dollar}和{dollar} rm Bsp {lcub} VI {rcub} {dollar }是第二和第六族元素，M是磁性过渡金属离子。我们已经探索了使用Mn {dollar} sp {lcub} ++ {rcub} {dollar}的电子顺磁共振（EPR）测量II-VI超晶格中单轴应变的可能性。这项工作的动机是，Mn {dollar} sp {lcub} ++ {rcub} {dollar}的EPR受晶体场的强烈影响。因此，可以自动预期应变引起的结晶场变化会对EPR光谱产生深远的影响。 EPR展示了各种新现象。我们已经观察到ZnTe / MnTe和CdTe / MnTe超晶格{dol} sp {lcub} 1,2 {rcub} {dollar}中Mn {dollar} sp {lcub} ++ {rcub} {dollar}的巨晶场分裂。 EPR光谱归因于从MnTe层扩散到ZnTe或CdTe层中的孤立Mn {dol} sp {lcub} ++ {rcub} {dollar}离子。此外，我们已经表明，这些位移可以用作此类超晶格中的应变仪，从而产生应变的大小，符号和均匀性。使用中子散射的结果比较与EPR的结果非常吻合。我们还测量了一系列{rm} Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub} Se {dollar}外延层系统的EPR。室温EPR线宽与x的关系为简单变化的二次关系，这提供了一种简单而精确的方法来确定外延层中Mn {dol} sp {lcub} ++ {rcub} {dollar}的浓度，其中{dol}} x> 0.05 {美元}。根据交换变窄理论分析了EPR线宽的温度依赖性，并确定了Dzyaloshinski-Moriya（DM）交换常数D {dollar} sb1 {dollar}，平均值为D {dollar} sb1 = 0.30 {dollar } K，与Larson的计算值合理吻合。最后，我们通过研究ZnTe / MnTe和CdTe / MnTe应变超晶格中的{dollar}-{lcub} 1over2 {rcub}到{lcub} 1over2 {rcub} {dollar}跃迁，研究了非常稀体系中的自旋-自旋相互作用。 。 EPR线宽的温度依赖性具有类似于在高x DMS系统中观察到的特征（幅度除外）：随着温度的降低而急剧扩大。根据交换变窄理论对线宽进行分析，得出令人惊讶的结果，即使在非常稀的Mn {dol} sp {lcub} ++ {rcub} {dol}浓度下，DM相互作用仍然是主要的磁性相互作用。 DM交互作用很小。

著录项

  • 作者

    Qazzaz, Ma'an.;

  • 作者单位

    University of Notre Dame.;

  • 授予单位 University of Notre Dame.;
  • 学科 Physics Condensed Matter.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 169 p.
  • 总页数 169
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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