Propagating Low-Energy 4f Paramagnons

传播低能 4f 顺磁振子

• 批准号: 523303368
• 负责人: Professor Dr. Sergej O. Demokritov, Ph.D.
• 金额: --
• 依托单位: Fakultät für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/523303368?language=en
• 关键词: Propagating; Low; Energy; 4f; Paramagnons

The concept of spin waves and their quanta magnons was introduced by F. Bloch in 1930. Today, the field of science investigating spin waves and magnons and utilizing them for data processing is known as magnonics. The typical materials used to investigate magnons are the magnetically ordered ferro- and anti-ferromagnets (FMs and AFMs) at temperatures below the critical (Curie or Neel) temperature. Above these temperatures, the magnetic order is lost, but the exchange stiffness, responsible for the spontaneous magnetic ordering, although decreases, remains finite. This phenomenon allowed for the observation of high-energy (> 10 meV) magnons also in the paramagnets (PMs) by inelastic neutron scattering. These magnons are called paramagnons. In the project "ParaMagnonics", we will apply a strong external magnetic field and will decrease the temperature of the PMs, to achieve the essential ordering of the magnetic moments. These quasi-independent moments will still be coupled by the remaining exchange-stiffness and/or by the dipole-dipolar interaction. Exploiting the variation of the materials, temperature and applied magnetic fields, we will prove the existence of propagating low-energy (< 0.5 meV) dipolar and exchange paramagnons in PMs and in FMs and AFMs above the critical temperatures. Consequently, we will investigate their dispersions, damping, and propagation characteristics. Our hypothesis is that paramagnons carried by 4f ions should have the fundamentally lowest damping values due to their isolation from the crystal lattice. Finally, we will exploit spin-orbit torque (SOT) phenomena to excite, amplify, and detect ballistic and diffusive paramagnons. We will use different PM and the family of Eu-chalcogenides of FM and AFM nature in particular. The paramagnons will be detected and characterized by low-temperature microwave and Brillouin Light Scattering spectroscopy. Electrical measurements and SOT phenomena will be utilized to understand the nature of the diffusive paramagnons spin transport as well as to excite and amplify them. ParaMagnonics has a very high degree of originality, as propagating low-energy paramagnons have never been observed experimentally and they have a whole range of advantages over ordinary magnons: a very broad class of PM materials for magnonics, low damping, sensitive control of paramagnon properties and new degrees of freedom for this control, and a novel toolbox for quantum magnonics.

自旋波及其量子磁振子的概念是由布洛赫在1930年提出的。今天，研究自旋波和磁振子并利用它们进行数据处理的科学领域被称为磁振学。用于研究磁振子的典型材料是温度低于临界温度（居里或尼尔）的磁有序铁磁体和反铁磁体（FMs和AFMs）。在这些温度以上，磁的有序性就丧失了，但是负责自发磁有序的交换刚度虽然降低了，但仍然是有限的。这一现象允许通过非弹性中子散射在顺磁体（pm）中观测高能（bbb10 meV）磁振子。这些磁振子被称为顺磁振子。在“顺磁”项目中，我们将施加一个强大的外部磁场并降低pm的温度，以实现磁矩的基本排序。这些准独立力矩仍将由剩余的交换刚度和/或偶极-偶极相互作用耦合。利用材料、温度和外加磁场的变化，我们将证明在临界温度以上的pm、FMs和AFMs中存在传播的低能（< 0.5 meV）偶极子和交换顺子。因此，我们将研究它们的色散、阻尼和传播特性。我们的假设是，由4f离子携带的顺子应该具有最低的阻尼值，因为它们与晶格隔离。最后，我们将利用自旋轨道扭矩（SOT）现象来激发、放大和探测弹道和扩散顺子。我们将使用不同的PM，特别是FM和AFM性质的eu -硫属化合物家族。利用低温微波和布里渊光散射光谱对顺子进行探测和表征。电测量和SOT现象将被用来理解扩散顺子自旋输运的性质，以及激发和放大它们。顺磁振子具有非常高的独创性，因为传播的低能量顺磁振子从未在实验中被观察到，它们比普通的磁振子具有一系列的优势：非常广泛的磁振子PM材料，低阻尼，对顺磁振子特性的敏感控制和这种控制的新自由度，以及量子磁振子的新工具箱。