Synchrotron X-ray Magnetic Scattering Studies under Strong Magnetic Fields

在这个项目中，我们旨在利用同步加速器x射线衍射技术来阐明高磁场下量子磁系统的磁性和结构变化。下面简要描述了从这个项目中获得的一些突出发现。(1)我们发现自旋- peierls化合物CuGeO_3在高场相的不通约性主要取决于临界场（〓12 T）附近的温度，而在足够高的场下则与温度无关。我们解释说，这一发现是由于抑制热波动的强磁场稳定了不相称状态。(2)在自旋1/2阶梯化合物Cu_2(C_5H_<12 bbb_n_2)_2Cl_4从自旋液体到长程有序相的临界场，预计会发生广义自旋- peierls跃迁，并发生晶格畸变。我们在世界最低温度0.04 K和高场条件下对该化合物的单晶进行了x射线衍射研究。我们发现沿a轴的晶格常数在临界场处呈现不连续变化。(3)对CeP进行了同步加速器x射线衍射测量，CeP是一个典型的致密近藤体系，尽管它的载流子浓度很小。在CeP中，两层像Ce一样的Γ_8层和一层像Ce一样的Γ_7层堆叠在一起，其周期随着外加磁场的变化而变化。从我们在高达14t的高油田进行的研究中，我们发现了8期和9期的新相。我们成功地研制了同步加速器x射线衍射的脉冲高场。我们构建了一个能产生高达35t的脉冲磁场而不破坏的分裂对磁体，并测量了一些化合物的x射线衍射。

In this project, we aim at clarifying the magnetic and structural changes in quantum magnetic systems under high magnetic fields using synchrotron X-ray diffraction technique. Some of the outstanding findings obtained from this project are briefly described below.(1)We have found that the incommensurability in the high field phase of a spin-Peierls compound, CuGeO_3 depends much on temperature near the critical field (〓12 T), while at high enough field it is independent of temperature. We have interpreted that this finding is due to a stabilization of the incommensurate state by a strong magnetic field which suppresses thermal fluctuations.(2)At the critical field from the spin liquid to a long-range ordered phase of a spin 1/2 ladder compound Cu_2(C_5H_<12>N_2)_2Cl_4,one expects a generalized spin-Peierls transition, in which a lattice distortion is predicted to occur. We have performed X-ray diffraction study on a single crystal of this compound at the World's lowest temperature of 0.04 K and at high fields. We have found that the lattice constant along the a-axis shows a discontinuous change at the critical field.(3)Synchrotron X-ray diffraction measurements have been performed on CeP which is a typical example of dense Kondo systems despite its small carrier concentration. In CeP two layers of Γ_8 like Ce and a layer of Γ_7 like Ce are stacked with a period which changes with an applied magnetic field. From our study performed in high fields up to 14 T we have discovered new phases with 8 and 9 periods.(4)We are successful in developing a pulsed high field for synchrotron X-ray diffraction. We have constructed a split pair magnet capable of producing pulsed field up to 35 T without destruction and measured X-ray diffraction on some compounds.