A Study of the Magnetic Properties of Some Strongly Correlated Electron Systems

最近在轻掺杂六硼化物Al-xLaxB6(A=Ca、Sr或Ba)中发现了高T_c弱铁磁性WF，这激发了人们对这一现象的理论和实验研究。虽然已经提出了几个模型，但解释仍然难以捉摸。为了更好地了解WF的起源，将在2K-1100K之间对受控样品进行电子顺磁共振(EPR)、单轴应力、微波吸收和磁化强度M的测量。此外，还将研究被称为多铁系统的Mf。它们同时是铁电的FE和铁磁的FM。有人认为BiMnO_3是MF。关于BiMnO_3的实验数据是不完整的。其磁性、电性和结构性质将通过EPR、M、比热、拉曼、X射线和电极化来测量。这项工作应该有助于理解目前存在的相互作用的性质，并促进这些化合物的未来工作。几名本科生和硕士研究生将参与到这个项目中来。他们将接受尖端研究技术方面的培训，这些技术为学生攻读博士学位或在工业领域就业提供了良好的准备。将进行选定的实验，以提供对这些系统的物理的新见解，这可能导致正确的理论模型。此外，还将对同时具有铁电和铁磁的化合物进行研究。尽管在这些系统中执行的工作很少，但可以想象一些重要的新应用。例如，多状态存储元件、电场控制的调频谐振装置和可变换能器。几名本科生和硕士研究生将参与到这个项目中来。他们将接受尖端研究技术方面的培训。这些都为博士项目或在工业领域的职业生涯提供了极好的准备。高中生和老师也将参加这个项目。

The recent discovery of high-Tc weak ferromagnetism, WF, in lightly doped hexaborides, A1-xLaxB6 (A = Ca, Sr, or Ba), has stimulated theoretical and experimental efforts to understand the this phenomenon. While several models have been proposed, an explanation is still elusive. In order to gain a better understanding of the origin of the WF, measurements by Electron Paramagnetic Resonance, EPR, uniaxial stress, microwave-absorption, and magnetization, M, in controlled samples will be conducted between 2 K - 1100 K. Also, systems known as multiferroics, MF, will be studied. They are simultaneously ferroelectric, FE, and ferromagnetic, FM. It has been suggested that BiMnO3 is MF. The experimental data on BiMnO3 is incomplete. Its magnetic, electrical and structural properties will be measured by EPR, M, specific heat, Raman, X-rays, and electric polarization. This work should help understand the nature of the interactions present and stimulate future work in these compounds. Several undergraduates and master's students will be involved in this program. They will be trained in cutting-edge research techniques, which provided the students excellent preparation for Ph.D. programs or for careers in industry. %%%The recent discovery of ferromagnetism in doped CaB6 is one of the great surprises in the modern study of magnetism for which there is still no explanation. Selected experiments will be carried out to provide new insight into the physics of these systems, which could lead to the correct theoretical model. Also, studies of compounds that are simultaneously ferroelectric, FE, and ferromagnetic, FM, will be carried out. Despite little work having been performed in these systems, a number of important new applications can be imagined. Examples are multiple state memory elements, electric field controlled FM resonance devices, and variable transducers. Several undergraduates and master's students will be involved in this program. They will be trained in cutting-edge research techniques. These provide excellent preparation for Ph.D. programs or for careers in industry. High school students and teachers will also participate in this program. This will continue the successful outreach program conducted by the PI's group in order to improve the quality of science education in K-12.***