Experimental Studies in High-Spin Molecular Magnets

高自旋分子磁体的实验研究

• 批准号: 0116808
• 负责人: Myriam Sarachik
• 金额: --
• 依托单位: CUNY City College
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0116808&HistoricalAwards=false
• 关键词: Experimental; Studies; Spin; Molecular; Magnets

This project investigates the magnetic properties of molecules containing clusters of magnetic atoms that are exchange coupled to produce a lattice of identical "nanomagnets; in particular, Mn12-Acetate and Fe8. These materials have a number of interesting properties: resonant spin tunneling, quantum interference (Berry's phase) effects in the magnetic relaxation, quantum coherent oscillations of the spin, and evidence for an abrupt crossover between thermally assisted magnetic relaxation and relaxation by pure quantum tunneling. Although much progress has been made, a full understanding of these materials awaits the resolution of a number of important issues, including the strength of spin-phonon coupling, the roles of dipolar interactions and hyperfine fields, and the nature of the crossover between thermally-assisted and pure quantum tunneling. Through measurements at very low temperatures using micron size Hall bars, this project will study the effect of externally applied transverse magnetic fields, the effect of microwave radiation, and to search for possible ferromagnetic or dipolar ordering. Molecular magnets are interesting from a fundamental point of view because they represent the borderline between classical and quantum magnetism. They are also interesting for their possible use for very high-density storage, and as potential candidates for elements in quantum computation. Graduate students involved in the project receive training in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry or government.Mn12-acetate and Fe8 are organic molecular crystals containing a very large number of regularly spaced, magnetically identical spin-10 clusters of a size that is borderline between the quantum and classical regimes. Interest in these materials has been sparked by a remarkable series of experimental observations of quantum-mechanical effects, including quantum tunneling of the spin magnetic moment, quantum-mechanical phase interference and the superposition of quantum states. Although much progress has been made, a full understanding of these materials awaits the resolution of a number of important issues, including the strength of the coupling of the spin magnetic moment to lattice vibrations, the roles of dipolar interactions and nuclear fields, and the nature of the crossover between the quantum and classical regimes. Through measurements at very low temperatures using micron size Hall bars, we propose to investigate the effect of externally applied transverse magnetic fields, the effect of microwave radiation, and to search for possible ferromagnetic or dipolar ordering. In addition to their interest for fundamental reasons, these materials are important for their possible use in very high-density storage, and as potential candidates for elements in quantum computation. Graduate students involved in the project receive training in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry or government.

该项目研究了包含磁性原子簇的分子的磁性，这些原子簇通过交换耦合产生相同的“纳米磁体”晶格；特别是mn12 -醋酸盐和Fe8。这些材料有许多有趣的特性：共振自旋隧穿，磁弛豫中的量子干涉（贝里相）效应，自旋的量子相干振荡，以及热辅助磁弛豫和纯量子隧道弛豫之间突然交叉的证据。尽管已经取得了很大的进展，但对这些材料的全面理解还有待解决一些重要问题，包括自旋声子耦合的强度、偶极相互作用和超精细场的作用，以及热辅助和纯量子隧道之间交叉的性质。通过在极低温度下使用微米大小的霍尔棒进行测量，该项目将研究外部施加的横向磁场的影响，微波辐射的影响，并寻找可能的铁磁或偶极有序。分子磁体从基本观点来看是有趣的，因为它们代表了经典磁性和量子磁性之间的边界。它们也很有趣，因为它们可能用于非常高密度的存储，并作为量子计算中元素的潜在候选者。参与该项目的研究生接受尖端技术的基础实验技术培训。这种培训将为他们在学术界、工业界或政府的一系列职业生涯做好准备。mn12 -醋酸盐和Fe8是有机分子晶体，含有大量规则间隔的，磁性相同的自旋10簇，其大小介于量子和经典政权之间。对这些材料的兴趣是由一系列引人注目的量子力学效应的实验观察引起的，包括自旋磁矩的量子隧穿，量子力学相干涉和量子态的叠加。虽然已经取得了很大的进展，但对这些材料的全面理解还有待解决一些重要问题，包括自旋磁矩与晶格振动的耦合强度，偶极相互作用和核场的作用，以及量子和经典制度之间交叉的性质。通过在极低温度下使用微米大小的霍尔棒进行测量，我们建议研究外部施加的横向磁场的影响，微波辐射的影响，并寻找可能的铁磁或偶极有序。除了它们的基本原因之外，这些材料对于它们在非常高密度存储中的可能应用以及作为量子计算中元素的潜在候选者也很重要。参与该项目的研究生接受尖端技术的基础实验技术培训。这种培训将为他们在学术界、工业界或政府的一系列职业生涯做好准备。