Study of the quantum properties and dissipative phenomena in molecular

分子量子特性和耗散现象的研究

• 批准号: 11440112
• 负责人: AJIRO Yoshitami
• 金额: $ 9.79万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440112/
• 关键词: nanoscale; quantum property; quantum energy level; dissipation; molecular magnet; polynuclear complex; pulse magnetization

The magnetic properties of molecular clusters attract considerable interest for the new physics involved and for the potential applications. At low temperatures, these molecules act as individual quantum nanomagnets, enabling to probe, at the macroscopic scale, the crossover between quantum and classical physics. Of fundamental interest is the situation of degeneracy of two magnetic levels, where quantum mechanical phenomena such as tunneling or coherence can occur. The situation of degeneracy between levels raises fundamental problems of quantum dynamics. A crucial issue is the role played by the coupling between magnetic molecular levels and the environment such as phonons. The purpose of this project is to verify experimentally the characteristic quantum energy levels and discuss the possible interplay between the anomalous magnetic relaxation phenomena and the level-crossings. For this purpose, a variety of model substances were synthesized by our group and some of them were kindly … More supplied by chemists. The representatives are dimers (binuclear complexes) such as Cs3Cr2C19 with X=Cl, Br, trimers (trinuclear complexes) such as A3Cu3(PO4)4 with A=Ca, Sr, trimerized chain system 3CuCl2・2dx, polynuclear molecular magnets such as Mn12, Fe12, V15 and so on We applied various complementary techniques, including advanced crystal preparation, nuclear magnetic resonance, electron spin resonance, neutron scattering, muon spin relaxation, high field magnetization as well as susceptibility and specific heat measurements, in cooperation with many other research groups. A high-field magnetization technique was applied to study the field-dependent behaviors of various kind of quantum spin systems by applying high magnetic field up to 54 T at temperature down to 0.1 K.For example, we observed successive phase transitions at three restricted field regions up to 40T in the S=2/3 dimerized system Cs3Cr2Cl9. Also, in Fe12 molecular magnet which forms a finite chain ring consisting of 12 Fe3+(S=5/2) ions, we observed five magnetization steps with equal field spacing, arising from energy-level crossings for the discrete quantum states in the finite spin system. In these examples, we discussed the structure of the energy levels an d the relaxation phenomena due to quantum spin dynamics in the metastable states around the level-crossing fields. Also, a high-frequency electron spin resonance (ESR) technique was applied for our purpose, in the wide temperature range down to 0.5 K, using high frequency sources up to 800 GHz. Examples are for the S=1/2 Heisenberg anttiferromagnetic chain system Cu-benzoate, Cu(C6H5COO)2・3H2O and for the trimerized chain system 3CuCl2・2dx, in which ferromagnetic trimers consisting of three S=1/2 spins coupled antiferromagnetically in one dimension.These results partly have been published already. Less

分子团簇的磁性因其所涉及的新物理和潜在的应用而引起人们的极大兴趣。在低温下，这些分子充当单独的量子纳米磁体，能够在宏观尺度上探测量子和经典物理之间的交叉。最基本的兴趣是两个磁能级的简并情况，在那里可以发生量子力学现象，如隧穿或相干。能级间简并的情况提出了量子动力学的基本问题。一个关键的问题是磁性分子能级和环境（如声子）之间的耦合所起的作用。本计画的目的是在实验上验证特征量子能级，并讨论异常磁弛豫现象与能级交叉之间可能的相互作用。为此，本课题组合成了多种模型物质，并对其中一些进行了亲切的研究。 ...更多信息 由化学家提供。代表物为二聚体（双核配合物），如Cs3 Cr2 C19，X=Cl，Br，三聚体（三核配合物）如A_3Cu_3（PO_4）_4（A=Ca，Sr），三聚链状体系3CuCl_2·2dx，多核分子磁体如Mn_（12），Fe_（12），V_（15）等。中子散射、μ子自旋弛豫、高场磁化以及磁化率和比热测量，与许多其他研究小组合作。采用高场磁化技术，在温度低至0.1 K的条件下，施加高达54 T的高磁场，研究了各种量子自旋系统的场依赖行为。例如，我们在S=2/3二聚体系Cs3 Cr2 Cl 9中观察到了高达40 T的三个限制场区域的连续相变。此外，在形成由12个Fe ~（3+）（S=5/2）离子组成的有限链环的Fe ~（12）分子磁体中，我们观察到五个等场间距的磁化阶跃，这是由有限自旋系统中离散量子态的能级交叉引起的。在这些例子中，我们讨论了能级结构和在能级交叉场附近的亚稳态中由于量子自旋动力学引起的弛豫现象。此外，高频电子自旋共振（ESR）技术应用于我们的目的，在宽的温度范围下降到0.5 K，使用高达800 GHz的高频源。例如，对于S=1/2的Heisenberg反铁磁链体系Cu-苯甲酸盐，Cu（C6 H5 COO）2·3 H2O和三聚链体系3CuCl 2·2dx，其中三个S=1/2自旋组成的铁磁三聚体在一维反铁磁耦合，这些结果部分已经发表。少

项目成果

Y.Inagaki et al: "High-Field Magnetization and High-Frequency ESR Study on the Tetranulear Cluster Composed of pi-Electrons(S=1/2)and d-Electrons (S=5/2)"Mol. Cryst. Liq. Cryst.. 343. 115-120 (2000)

Y.Inagaki等人：“由π电子(S=1/2)和d-电子(S=5/2)组成的四核团簇的高场磁化和高频ESR研究”Mol。

Y.Ajiro et al.: "μSR Study of 1:1 Complex of {Mn(hfac)_2} with・・・"Mol.Cryst.and Liq.Cryst.. (in press). (2000)

Y.Ajiro 等人：“{Mn(hfac)_2} 与...的 1:1 复合物的 μSR 研究”Mol.Cryst.and Liq.Cryst..（出版中）。

Y.Ajiro et al.: "Magnetism of 1D quantum Ferrimagnets, A3Cu3(PO4)4 with A=Ca,Sr"J.Phys.Soc.Jpn.. 70(in press). (2001)

Y.Ajiro 等人：“1D 量子亚铁磁体的磁性，A3Cu3(PO4)4 with A=Ca,Sr”J.Phys.Soc.Jpn.. 70（出版中）。

M.Mekata et al.: "Ground state of the geometrically frustrated system・・・"Phys.Rev.. B61. 4088-4092 (2000)

M.Mekata 等人：“几何受挫系统的基态……”Phys.Rev.. B61 (2000)。

Y.Ajro et al: "mSR Study of 1 : 1 Complex of {Mn(hfac)2} with diazodi(4-pyridyl)methan as a Photoresponsible Magnetic Coupler"Mol. Cryst. Liq. Cryst.. 343. 103-108 (2000)

Y.Ajro 等人：“{Mn(hfac)2} 与重氮二(4-吡啶基)甲烷的 1:1 配合物作为光响应磁耦合剂的 mSR 研究”Mol。