Kimel A V, Kirilyuk A, Tsvetkov A, Pisarev R V, Rasing Th
NSRIM Institute, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
Nature. 2004 Jun 24;429(6994):850-3. doi: 10.1038/nature02659.
All magnetically ordered materials can be divided into two primary classes: ferromagnets and antiferromagnets. Since ancient times, ferromagnetic materials have found vast application areas, from the compass to computer storage and more recently to magnetic random access memory and spintronics. In contrast, antiferromagnetic (AFM) materials, though representing the overwhelming majority of magnetically ordered materials, for a long time were of academic interest only. The fundamental difference between the two types of magnetic materials manifests itself in their reaction to an external magnetic field-in an antiferromagnet, the exchange interaction leads to zero net magnetization. The related absence of a net angular momentum should result in orders of magnitude faster AFM spin dynamics. Here we show that, using a short laser pulse, the spins of the antiferromagnet TmFeO3 can indeed be manipulated on a timescale of a few picoseconds, in contrast to the hundreds of picoseconds in a ferromagnet. Because the ultrafast dynamics of spins in antiferromagnets is a key issue for exchange-biased devices, this finding can expand the now limited set of applications for AFM materials.
铁磁体和反铁磁体。自古以来，铁磁材料就有广泛的应用领域，从指南针到计算机存储，以及最近的磁性随机存取存储器和自旋电子学。相比之下，反铁磁（AFM）材料虽然占磁有序材料的绝大多数，但长期以来仅具有学术研究价值。这两种磁性材料的根本区别体现在它们对外加磁场的反应上——在反铁磁体中，交换相互作用导致净磁化强度为零。相关的净角动量缺失应会导致反铁磁体自旋动力学快几个数量级。我们在此表明，使用短激光脉冲，反铁磁体TmFeO3的自旋确实可以在几皮秒的时间尺度上被操控，这与铁磁体中的数百皮秒形成对比。由于反铁磁体中自旋的超快动力学是交换偏置器件的关键问题，这一发现可以拓展目前反铁磁材料有限的应用范围。
