Physics of rare earth - transition metal permanent magnets: theory of their magnetostriction

永磁体在已建立和发展中的技术中都很普遍。在电动机和发电机、传感器、磁力机械设备以及磁场和成像系统中发现，它们在全球有数十亿磅的市场。它们在基础材料物理学方面也是迷人的和具有挑战性的。在沃里克大学和伯明翰大学，EPSRC资助的一个综合性理论实验方案-PRETAMAG项目（稀土过渡金属铝永磁网设计原理的物理研究）-正在揭示关键的设计原理。这个博士项目是这一努力的一部分，将致力于发展重要的磁结构和磁弹性效应的理论。该项目将涉及凝聚态物理理论和高性能计算。大多数强磁体由稀土（RE）和过渡金属（TM）原子以特定的晶体结构排列而成。TM元素，如铁或钴，有助于铁磁性持续到高温，而RE组分，如钐或钕，在那里产生大的磁化强度，这很难从晶体结构指定的容易方向重新取向。现在，全世界都在共同努力，开发具有改善的磁特性和减少对关键元素依赖的新型永磁材料。磁铁中的每个稀土原子都有一个磁矩，这是由它的近局域化的f-电子建立的。这些时刻沉浸在来自所有RE和TM原子的数十亿个价电子的胶水中。与TM原子相关的局部磁矩也可以从这种复杂的电子流体中出现。我们将建立和应用一个理论（见1），它提供了一个无参数的准确的帐户，这种物理，并使预测建模的温度，成分和结构的RE-TM磁体的磁硬度的依赖性。在每个阶段，我们将通过与详细的实验测量进行比较来测试和改进理论。

Permanent magnets are pervasive in both established and developing technologies. Found in motors and generators, transducers, magnetomechanical devices and magnetic field and imaging systems, there is a multi-billion pound worldwide market for them. They are also both fascinating and challenging in terms of their fundamental materials physics. At the Universities of Warwick and Birmingham an integrated EPSRC-funded theory-experiment programme - the PRETAMAG project (Investigations of the Physics underlying the principles of design of Rare Earth Transition metAl permanent MAGnets) - is uncovering key design principles. This PhD project is part of this effort and will be directed at developing the theory for important magneto-structural and magnetoelastic effects. The project will involve condensed matter physics theory and high performance computing.Most strong magnets are comprised of rare earth (RE) and transition metal (TM) atoms arranged in specific crystal structures. The TM element, such as iron or cobalt, helps the ferromagnetism to persist to high temperatures and the RE component, such as samarium or neodymium, is there to generate a large magnetisation which is hard to reorientate away from an easy' direction specified by the crystal structure. There is now a concerted effort worldwide to come up with new permanent magnetic materials with improved magnetic characteristics and reduced dependence on critical elements. Each RE atom in the magnet has a magnetic moment which is set up by its nearly localised f-electrons. These moments are immersed in a glue of septillions of valence electrons coming from all the RE and TM atoms. Local magnetic moments associated with the TM atoms can also emerge from this complex electron fluid. We will establish and apply a theory (see 1) which provides a parameter-free accurate account of this physics and enables predictive modelling of the temperature, compositional and structural dependence of the magnetic hardness of the RE-TM magnets. At each stage, we will test and improve the theory by comparison with detailed experimental measurements.