Mapping magnetic anisotropy: rational design of high-blocking temperature nanomagnets

磁性材料在我们的日常生活中无处不在，我们依赖于存储数据的设备，而不需要考虑第二个问题，期望下一个小工具更小，存储容量更大。用于存储数据的材料是使用“自上而下”的方法制成的：以这种方式制成的磁性颗粒不能无限期地继续减小尺寸，因为热激活磁化反转将导致数据丢失。然而，使用“自下而上”的方法，我们可以生产磁性分子，这些分子易于合成，价格便宜，并且是单分散的。因此，我们可以设想在超高Pbit /in 2密度的信息存储，通过使用表面上的分子位的自组装阵列，每个分子的尺寸只有几纳米。虽然这些分子很容易合成，但目前的方法对分子的结构几乎没有控制，因此，对所得磁性的控制有限。因此，这些具有潜在吸引力的分子仅在非常低的温度下才显示出其有趣的磁性。为了提高所谓的阻塞温度，我们需要开发更高水平的控制。关键的要求是分子具有与自旋基态相关的大的易轴磁各向异性。然而，控制磁性分子各向异性的规则还没有得到很好的理解。通过合成这些分子的家族和调整结构，沿着进行详细的磁性测量和理论计算，我们将开发确定整体各向异性的磁结构相关性。因此，我们将调整和增加磁各向异性，为高阻断温度磁性分子的生产提供前所未有的控制水平。

Magnetic materials are all around us in everyday life and we rely on devices that store data without a second thought, expecting the next gadget to be smaller and with an increased storage capacity. The materials used to store data are made using a 'top-down' approach: magnetic particles made in this way can not continue to decrease in size indefinitely, as thermally activated magnetization reversal will lead to data loss. However, using a 'bottom-up' approach, we can produce magnetic molecules, which are easy to synthesise, cheap and are monodisperse. Hence, we can envisage information storage at ultra-high Pbit / in2 densities, by using a self-assembled array of molecular bits on a surface, with each molecule just a few nanometres in size.Although these molecules are easy to synthesise, current approaches afford little control over the structure of the molecule and hence, limited control over the resultant magnetic properties. Therefore, these potentially fascinating molecules display their interesting magnetic properties only at very low temperatures. To increase the so-called blocking temperature, we need to develop much greater level of control. The key requirement is that the molecule has a large easy-axis magnetic anisotropy associated with the spin ground state. However, the rules for controlling the anisotropy of magnetic molecules are not well understood. By synthesising families of these molecules and tuning the structure, along with detailed magnetic measurements and theoretical calculations, we will develop the magnetostructural correlations that determine the overall anisotropy. Hence, we will tune and increase the magnetic anisotropy, providing an unprecedented level of control in the production of high-blocking temperature magnetic molecules.