Magnetic structure of Dy-Y superlattices.
Magnetic structure of Dy-Y superlattices.
复制标题
Dy-Y 超晶格的磁性结构。
DOI：
10.1103/physrevb.35.6808
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Flynn
中科院分区：
文献类型：
--
作者：
Erwin;Rhyne;Salamon;Borchers;Sinha;Du;Cunningham;Flynn
通过中子衍射显示，通过分子束外延技术产生的两个 Dy-Y 超晶格样品在与双层厚度不相称的螺旋中磁性有序。一个样品由 64 个双层组成，每个双层由约 15 个 Dy 原子生长平面 (42 A) 和随后的 14 个 Y 原子平面 (38 A) 组成。第二个样品有90层，每层由9个Dy原子平面和8个Dy/sub 0.5/Y/sub 0.5/合金平面组成。这种排序的相位相干性延伸到多个双层，并且在局部 Dy 自旋层被非磁性 Y 的 14 个原子平面分隔开的样品中尤其引人注目。螺旋手性跨多个双层传播的事实排除了 Y 层两侧的 Dy 平面之间的简单标量 Ruderman-Kittel-Kasuya-Yosida 耦合，但表明在 Y 传导中诱发了螺旋自旋密度波电子。超晶格结构因子的简单模型表明，观察到的磁衍射峰强度的不对称性可以归因于每种层类型（Dy 和 Y）中存在不同的磁调制波矢量。在这些超晶格中，插入的非 Dymore 层和基底的应变钳位抑制了在零场和有限场中体状 Dy 中发现的一阶铁磁转变。尽管平面磁致伸缩被钳制，但观察到在基面施加磁场会在低温下产生向亚稳态铁磁态的二阶不可逆转变。在高温下，由于与未补偿的 Dy 层矩的随机场耦合，螺旋相干长度减小，从而引发磁化过程。« less
Two samples of Dy-Y superlattices produced by molecular-beam-epitaxy techniques are shown by neutron diffraction to order magnetically in a helix which is incommensurate with the bilayer thickness. One sample consists of 64 bilayers, each bilayer made up of about 15 growth planes (42 A) of Dy atoms followed by 14 planes (38 A) of Y atoms. The second sample has 90 layers, each layer consisting of 9 Dy atomic planes and 8 Dy/sub 0.5/Y/sub 0.5/ alloy planes. The phase coherence of this ordering extends over several bilayers, and is especially striking in the sample where the layers of localized Dy spins are separated by 14 atomic planes of nonmagnetic Y. The fact that the helix chirality propagates across several bilayers rules out a simple scalar Ruderman-Kittel-Kasuya-Yosida coupling between the Dy planes on either side of an Y layer, but suggests instead that a helical spin density wave is induced in the Y conduction electrons. A simple model for the superlattice structure factor demonstrates that observed asymmetries in the magnetic diffraction-peak intensities can be ascribed to the existence of different magnetic modulation wave vectors in each layer type (Dy and Y). In these superlattices the strain clamping by the intervening non-Dymore » layers and the substrate suppresses the first order ferromagnetic transition found in bulk Dy in both zero and finite fields. Although the planar magnetostriction is clamped, it is observed that the application of a magnetic field in the basal plane produces at low temperatures a second order irreversible transition to a metastable ferromagnetic state. At high temperature the magnetization process is initiated by a reduction of the helical coherence length due to a random-field coupling to the uncompensated Dy layer moment.« less