Department of Applied Physics, Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
Small. 2019 Jan;15(1):e1804557. doi: 10.1002/smll.201804557. Epub 2018 Nov 21.
The rapid growth in demand for data and the emerging applications of Big Data require the increase of memory capacity. Magnetic memory devices are among the leading technologies for meeting this demand; however, they rely on the use of ferromagnets that creates size reduction limitations and poses complex materials requirements. Usually magnetic memory sizes are limited to 30-50 nm. Reducing the size even further, to the ≈10-20 nm scale, destabilizes the magnetization and its magnetic orientation becomes susceptible to thermal fluctuations and stray magnetic fields. In the present work, it is shown that 10 nm single domain ferromagnetism can be achieved. Using asymmetric adsorption of chiral molecules, superparamagnetic iron oxide nanoparticles become ferromagnetic with an average coercive field of ≈80 Oe. The asymmetric adsorption of molecules stabilizes the magnetization direction at room temperature and the orientation is found to depend on the handedness of the chiral molecules. These studies point to a novel method for the miniaturization of ferromagnets (down to ≈10 nm) using established synthetic protocols.
对数据的需求迅速增长，大数据的新兴应用要求增加内存容量。磁性存储设备是满足这一需求的主要技术之一；然而，它们依赖于使用铁磁体，这就产生了尺寸减小的限制，并对材料提出了复杂的要求。通常，磁性存储的尺寸限制在 30-50nm 范围内。进一步减小尺寸，达到 ≈10-20nm 的规模，会使磁化变得不稳定，其磁取向容易受到热波动和杂散磁场的影响。在本工作中，我们展示了可以实现 10nm 单畴铁磁性。通过使用手性分子的不对称吸附，超顺磁性氧化铁纳米颗粒变得具有铁磁性，平均矫顽力约为 80Oe。分子的不对称吸附在室温下稳定了磁化方向，并且发现其方向取决于手性分子的手性。这些研究为使用既定的合成方案将铁磁体（缩小到 ≈10nm 以下）小型化提供了一种新方法。
