Interface induced magnetic properties of thin films

由于在铁磁(FM)/非磁性(NM)多层膜中发现了界面感应现象，使得磁记忆存储密度在过去三十年中的快速增长成为可能。巨磁电阻和隧道磁阻现象的发现使磁矩方向的检测成为可能，是设计磁性传感器的关键，这种传感器可以将硬盘驱动器的记录密度提高100倍。用来操纵磁矩方向的自旋转移扭矩(STT)和自旋轨道扭矩的观测允许一种新的固态非易失性磁存储器的设计，该存储器被认为是存储器件中的下一代。另一个被广泛研究的界面效应是层间交换耦合。由于传统的耦合层只允许FM层的磁矩共线取向，这种现象到目前为止还没有被充分利用。最近，我们发现并申请了专利的新型耦合层(CL)材料，可以替代NM，插入两个铁磁层之间，以精确控制FM|CL|FM中FM层的磁矩的相对取向。这些新的耦合层具有用于大多数磁性纳米器件的潜力，因为磁性纳米器件的优化设计几乎总是要求至少两个相邻的铁磁层之间非共线对准。*本提案的重点是了解FM|CL|FM结构中非共线耦合的起源，以及如何将这些结构结合到磁性纳米器件中。重点将放在可以从磁矩的非共线排列、自旋转移扭矩磁性随机存取存储器(STT MRAM)和纳米振荡器中受益最大的器件上。与当前最先进的STT MRAM设备相比，具有非共线磁矩对齐的STT MRAM有望具有更快的写入速度和显著的低功耗。加拿大将从已经并将产生的重大知识产权中受益，这将为HQP在加拿大开发这些纳米器件创造机会。*除了研究静态效应，如层间耦合，我们还将研究磁化动态效应，FM|NM界面的自旋泵浦，以及随后纯自旋电流在NM中的传输。特别令人感兴趣的是NM=铂和钯，因为它们在与铁磁性薄膜连接时表现出接近磁化。铂和钯对铁磁层的静态和动态磁性能也有很大影响，这可能是有益的，如表面各向异性的增加，也可能是不利的，如增加磁阻尼值。我们将通过自旋泵浦和逆自旋霍尔效应研究与铂和钯相邻的铁磁层的损耗增加的机制。

The rapid increase in magnetic memory storage density over the last three decades has been made possible by the discovery of interface-induced phenomena in ferromagnetic (FM)|non-magnetic (NM) multilayers. The discovery of giant magnetoresistance and tunnel magnetoresistance phenomena enabled the detection of magnetic moment direction and are key for the design of magnetic sensors that are responsible for >100 times increase in the recording density of hard drives. The observation of spin transfer torque (STT) and spin orbit torque, utilized to manipulate the magnetic moment direction, allows for a novel design of solid state non-volatile magnetic memories, which are identified as the next generation in memory devices. ******Another interface effect that has been intensively studied is the interlayer exchange coupling. This phenomenon has not been used to its full potential until now, since traditional coupling layers only allow for collinear orientation of magnetic moments of FM layers. Recently, we discovered and patented new coupling layer (CL) materials, which can be inserted instead of NM, between two ferromagnetic layers to precisely control the relative orientation of the magnetic moments of FM layers in FM|CL|FM. These new coupling layers have the potential to be used in the majority of magnetic nanodevices since the optimal design of magnetic nanodevices almost always requires non-collinear alignment between at least two neighboring ferromagnetic layers. ******This proposal focuses on understanding the origin of non-collinear coupling in FM|CL|FM structures and how to incorporate these structures into magnetic nanodevices. The emphasis will be on devices, which could benefit most from non-collinear alignment of magnetic moments, spin transfer torque magnetic random-access memories (STT MRAM), and nano-oscillators. STT MRAM with non-collinear alignment of magnetic moments are expected to have much faster write speeds and significantly low power consumption than the current state-of-the-art STT MRAM devices. Canada will benefit from significant intellectual property that has already been and will be generated, which could create an opportunity for HQP to develop these nanodevices in Canada.******In addition to studying static effects, such as interlayer coupling, we will also study magnetization dynamic effects, spin pumping at FM|NM interfaces, and the subsequent transport of pure spin current in NM. Of specific interest are NM = Pt and Pd since they exhibit proximity magnetization when interfaced with ferromagnetic films. Pt and Pd also strongly affect magnetic static and dynamic properties of ferromagnetic layers, which can be beneficial like increase of surface anisotropy or detrimental like increase of magnetic damping. We will study the mechanisms responsible for increase of damping of ferromagnetic layers adjacent to Pt and Pd by means of spin pumping and inverse spin Hall effect.**