Transport and Magnetic Properties of Disordered Cr2AlC MAX Phases (TRANSMAX)

由过渡金属碳化物或氮化物分子的二维层（被后过渡金属原子层隔开）组成的材料（所谓的MAX相）因其出色的机械性能而众所周知，并且已发现作为高温涂层的应用。然而，它们的纳米层状结构对电子传输也有巨大的影响，赋予了类似金属的导电性。在这里，我们的目标是研究磁掺杂MAX相磁输运应用的潜力，从而产生鲁棒的，耐温的介观器件。为了继续关注应用，我们选择了Cr2 AlC，这是一种工业相关的MAX相。特别是，我们专注于纳米层状结构，并部署离子辐照诱导系统的变化，在界面处的结构有序。此外，我们将应用离子束掺杂使用磁性元素。理解上述现象对于识别和优化磁输运的最大相位是必要的。携带磁矩的高能离子，例如Co+、Mn+、Fe+等将被用作磁性掺杂剂，而稀有气体离子，例如Ar+将被用于控制在辐照过程期间产生的无序效应。无序化的程度可以通过离子注量和能量来控制。初步工作表明，MAX接口的敏感无序，在~0.1 Co+/nm 2的通量，可以导致大的增强的磁阻，与非线性依赖的整体电阻的无序。纯无序与Ar+离子也可以导致增加的磁化，这表明通过无序的电子结构的强烈变化。在我们之前的项目中，已经对磁掺杂MAX相进行了研究，目的是使用磁化作为高温涂层完整性的实时指标。在拟议的36个月项目中，将对商业来源的MAX层进行详细调查。离子辐照的设计和实施及其对微结构影响的研究将在离子束中心（HZDR）进行。此外，低温运输测量光刻运输设备将在德累斯顿工业大学进行。一名共享的博士生将接受洁净室工艺（HZDR）和运输测量（TUD）方面的培训。在Cr2 AlC系统上获得的见解可能为各种离子无序MAX相作为磁输运材料的应用铺平道路。

Materials composed of two-dimensional layers of transition metal carbide or nitride molecules separated by layers of post-transition metal atoms, the so-called MAX phases, are well known for their outstanding mechanical properties and have found applications as high temperature coatings. Their nano-lamellar structure however, also has huge implications on the electronic transport, imparting a metal-like conductivity. Here we aim to investigate the potential of magnetically doped MAX phases for magneto-transport applications, leading to robust, temperature resistant mesoscopic devices. In continuation of the applications-focus, we select the Cr2AlC, an industrially-relevant MAX phase. In particular, we focus on the nano-lamellar structure, and deploy ion-irradiation to induce systematic changes to the structural ordering at the interface. Moreover we will apply ion-beam-doping using magnetic elements. Understanding of the above phenomena is necessary to identify and optimize MAX phases for magneto-transport. Energetic ions carrying magnetic moments, such as Co+, Mn+, Fe+ etc. will be used as magnetic dopants, whereas noble gas ions, such as Ar+ will be used to control the effects of disordering generated during the irradiation process. The degree of disordering can be controlled via the ion fluence and energy. Preliminary work shows that the sensitive disordering of the MAX interfaces, at ~0.1 Co+/nm2 fluence, can lead to a large enhancement of magneto-resistance, with a non-linear dependence of the overall resistance on the disorder. Pure disordering with Ar+ ions can also lead to increased magnetization, suggesting strong variation of the electronic structure through disorder. In our previous project, investigations on magnetically doped MAX phases have been made, with the aim of using the magnetization as an on-the-fly indicator of the integrity of the high-temperature coating. In the proposed 36-month project, a detailed investigation on commercially sourced MAX layers will be performed. Design and implementation of ion-irradiation and an investigation of its effects on the microstructure will be performed at the Ion Beam Centre (HZDR). In addition, low temperature transport measurements on lithographed transport devices will be performed at the TU Dresden. A shared PhD student will be trained on clean-room processes (HZDR) as well as in transport measurements (TUD). The insights gained on the Cr2AlC system may pave the way for applications of a variety of ion-disordered MAX phases as materials for magneto-transport.