Fe-Pd-X Thin Film-Polymer Composites for Sensor Applications - First-principles evaluation of magneto-crystalline anisotropy and related intrinsic properties of Fe-Pd-X: optimization of alloy composition

该项目是旨在开发用于传感器应用的新型磁性形状记忆Fe-Pd-X合金的合作的一部分。磁性形状记忆合金（MSMA）是近年来研究的热点。它们是感兴趣的致动器应用，由于大的磁致应变高达10%的Ni 2 MnGa。然而，这种材料的应用受到限制，由于低粘连力。一种有前途的MSMA是Fe 70 Pd 30合金，其具有较小的应变，但具有10 MPa的显著更高的阻塞应力。通过添加第三元素来优化该合金是必要的，以促进其在传感器中的应用。在这里，第一性原理计算被设想为（i）获得对Fe-Pd合金的本征性质（自发磁化、四元畸变、磁晶各向异性）的基本理解，以及（ii）预测如果添加其他元素以产生三元（四元）Fe-Pd-X（-Y）系统，本征性质的变化。虽然在低外场和外应力消失时的场致应变与自发磁化强度成正比，但可实现的最大应变和阻挡应力不可避免地取决于磁晶各向异性能。因此，要判断某种合金的技术适用性，就必须了解这两种固有特性。另一方面，MSMA的磁晶各向异性难以测量。因此，第一性原理计算是需要的预期性能的预测和测量数据的理解。

This project is part of a collaboration aiming at new magnetic shape memory Fe-Pd-X alloys for sensor applications. Magnetic shape memory alloys (MSMA) have received much attention in recent years. They are of interest for actuator applications due to large magnetically induced strains of up to 10% in Ni2MnGa. However, application of this material is restricted due to low blocking forces. A promising MSMA is the Fe70Pd30 alloy with smaller strains but significantly higher blocking stresses of 10 MPa. Optimization of this alloy by adding third elements is necessary to facilitate its application in sensors. Here, first-principles calculations are envisaged to (i) gain fundamental understanding of the intrinsic properties (spontaneous magnetization, tetragonal distortion, magneto-crystalline anisotropy) of Fe-Pd alloys and (ii) predict the change of intrinsic properties if other elements are added to produce ternary (quaternary) Fe-Pd-X(-Y) systems. While the field-induced strain at low external field and vanishing external stress is proportional to the spontaneous magnetization, the achievable maximum strain and the blocking stress are unavoidably determined by the magneto-crystalline anisotropy energy. Thus, knowledge of both intrinsic properties is necessary to judge the technological applicability of a certain alloy. On the other hand, the magneto-crystalline anisotropy of MSMA is difficult to measure. Thus, first-principles calculations are needed both for the prediction of expected properties and for the understanding of measured data.