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首页> 外文学位 >Microwave magnetic resonances in solids: Part I. Electron paramagnetic resonance in diluted magnetic semiconductors (DMS). Part II. Magnetic dimensional resonances in magnetite spheres.
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Microwave magnetic resonances in solids: Part I. Electron paramagnetic resonance in diluted magnetic semiconductors (DMS). Part II. Magnetic dimensional resonances in magnetite spheres.

机译：固体中的微波磁共振：第一部分。稀释磁性半导体（DMS）中的电子顺磁共振。第二部分磁铁矿球体中的磁维共振。

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摘要

In part I, we present the results of electron paramagnetic resonance (EPR) studies in two systems of diluted magnetic semiconductors--{dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Te{dollar}, {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Se{dollar}, {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}S{dollar}, and in {dollar}rm Cdsb{lcub}1-x-y{rcub}Mnsb{lcub}x{rcub}Fesb{lcub}y{rcub}Se{dollar}.; In the case of the Zn-based DMS alloys, we have analyzed the high temperature EPR linewidth as a function of the Mn concentration x, temperature T, and anion (Te, Se or S) and the cation (Cd or Zn), using the exchange narrowing theory. Our results are in agreement with those of previous investigators. As in the case of the Cd based DMS, our results confirm that the Dzyaloshinskii-Moriya (D-M) anisotropic exchange interactions are the major source of broadening in {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Te{dollar} and in {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Se{dollar}. In the sulphides, the contribution from the dipolar and D-M interactions are nearly equal. Taking into account the corrections due to single ion anisotropies and Mn-associated D-M interactions, a better quantitative agreement is obtained between theory and experiment, especially in the case of the sulphides. From the extrapolated value of the infinite temperature linewidth in {dollar}rm Znsb{lcub}1-x{rcub}Mnsb{lcub}x{rcub}Te{dollar}, we can extract the nearest neighbour D-M exchange constant, which is in good agreement with the theoretically predicted values of Larson et al.; More importantly, the anion dependence of the linewidth is in reasonable agreement with the theory. Our results also show that the EPR lines are broader in the Zn-based DMS alloys than in the Cd alloys for equal values of x, T and the same anion. The agreement with the theoretical predictions is best for the tellurides, and worsens for the selenides and sulphides. In almost all the samples investigated, the linewidth varies linearly as {dollar}vertThetavert{dollar}/T, where {dollar}Theta{dollar} is the Curie-Weiss temperature. This behavior is true even when the condition for the high temperature limit (T {dollar}gg vertThetavert{dollar}) is not satisfied, indicating that the theory was satisfied for a broader range of conditions, which is encouraging.; Our results for EPR in {dollar}rm Cdsb{lcub}1-x-y{rcub}Mnsb{lcub}x{rcub}Fesb{lcub}y{rcub}Se{dollar} show that the lines are dramatically broadened as y is increased for nearly equal values of x, even for very small values of y(y {dollar}<{dollar} 0.01). We assume that this broadening is due to the rapid spin-lattice relaxation of the Fe{dollar}sp{lcub}+2{rcub}{dollar} ions.; In Part II, we describe a series of new magnetic resonances observed in magnetite ({dollar}rm Fesb3Osb4{dollar}) spheres. (Abstract shortened with permission of author.)
机译：在第一部分中，我们介绍了在两个稀磁半导体系统中的电子顺磁共振（EPR）研究的结果-{dol} rm Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub} Te {dollar }，{美元} rm Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub} Se {dollar}，{美元} rm Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub } S {dollar}，以及{dollar} rm Cdsb {lcub} 1-xy {rcub} Mnsb {lcub} x {rcub} Fesb {lcub} y {rcub} Se {dollar}。对于Zn基DMS合金，我们已经分析了高温EPR线宽与Mn浓度x，温度T和阴离子（Te，Se或S）和阳离子（Cd或Zn）的关系，交易收窄理论。我们的结果与以前的研究人员的结果一致。与基于Cd的DMS一样，我们的结果证实Dzyaloshinskii-Moriya（DM）各向异性交换相互作用是{rm} rm Znsb {lcub} 1-x {rcub} Mnsb {lcub} x扩展的主要来源{rcub} Te {dollar}和{dol} rm Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub} Se {dollar}。在硫化物中，偶极和D-M相互作用的贡献几乎相等。考虑到由于单离子各向异性和Mn相关的D-M相互作用引起的校正，理论和实验之间获得了更好的定量一致性，尤其是在硫化物的情况下。根据{rm} Znsb {lcub} 1-x {rcub} Mnsb {lcub} x {rcub} Te {dollar}中无限温度线宽的外推值，我们可以提取最近的DM交换常数，即与Larson等人的理论预测值良好吻合；更重要的是，线宽对阴离子的依赖性与理论相符。我们的结果还表明，对于x，T和相同的阴离子，Zn基DMS合金中的EPR线比Cd合金中的EPR线宽。与理论预测的一致性最适合于碲化物，而对于硒化物和硫化物则更糟。在几乎所有调查的样本中，线宽都按{dollar} vertThetavert {dollar} / T线性变化，其中{dollar} Theta {dollar}是居里-魏斯温度。即使在不满足高温极限条件（T {dollar} gg vertThetavert {dollar}）的情况下，这种行为也是正确的，这表明该理论在更大范围的条件下都得到了满足，这是令人鼓舞的。我们对{dollar} rm Cdsb {lcub} 1-xy {rcub} Mnsb {lcub} x {rcub} Fesb {lcub} y {rcub} Se {dollar}中的EPR的结果表明，随着y的增加，线显着加宽x的值几乎相等，即使y的值很小（y {dollar} <{dollar} 0.01）。我们假设这种扩展是由于Fe {dollar} sp {lcub} +2 {rcub} {dollar}离子的快速自旋晶格弛豫。在第二部分中，我们描述了在磁铁矿（{rm} Fesb3Osb4 {dollar}）球体中观察到的一系列新的磁共振。 （摘要经作者许可缩短。）

著录项

  • 作者

    Rajagopalan, Sridevi.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 1988
  • 页码 216 p.
  • 总页数 216
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

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