Interface induced magnetic properties of thin films

在过去的三十年中，由于在铁磁（FM）|非磁（NM）多层材料中发现了界面诱导现象，使得磁存储密度的快速增长成为可能。巨磁阻和隧道磁阻现象的发现使磁矩方向的检测成为可能，是磁传感器设计的关键，使硬盘的记录密度提高了100倍。利用自旋传递转矩（STT）和自旋轨道转矩来控制磁矩方向，可以设计一种新的固态非易失性磁存储器，被认为是下一代存储器件。另一个被深入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调频层磁矩的共线取向，因此这种现象直到现在还没有充分发挥其潜力。最近，我们发现了一种新的耦合层（CL）材料，它可以代替NM插入两个铁磁层之间，以精确控制FM|CL|调频中FM层磁矩的相对方向。这些新的耦合层有潜力用于大多数磁性纳米器件，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铁磁层之间的非共线排列。本研究的重点是了解FM|CL|FM结构中非共线耦合的起源，以及如何将这些结构整合到磁性纳米器件中。重点将放在器件上，这些器件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）和纳米振荡器中获益最多。与目前最先进的STT MRAM设备相比，具有磁矩非共线对准的STT MRAM预计具有更快的写入速度和显着的低功耗。加拿大将从已经和将要产生的重要知识产权中受益，这可能为HQP在加拿大开发这些纳米器件创造机会。除了研究层间耦合等静态效应外，我们还将研究磁化动态效应、FM|纳米界面的自旋泵浦以及随后在纳米中纯自旋电流的输运。特别感兴趣的是NM = Pt和Pd，因为它们在与铁磁薄膜界面时表现出接近磁化。Pt和Pd对铁磁层的静态和动态磁性能也有强烈的影响，可能是有利的，如表面各向异性的增加，也可能是有害的，如磁阻尼的增加。我们将利用自旋抽运和逆自旋霍尔效应研究Pt和Pd附近铁磁层阻尼增加的机理。

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.