Materials World Network: Ultrafast All-Optical Switching in Ferri-/Ferromagnetic Nanomagnets

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Nanomagnets have been under consideration for next generation data storage media and other spintronics applications for some time. Recently, the discovery of ultrafast all-optical switching of magnetic orientation in ferrimagnetic materials has received a lot of interest. The potential combination of such an optical switching layer with an exchange-coupled ferromagnetic storage layer is highly intriguing and raises a number of exciting material questions. This project will systematically explore FeTb-FePtCu heterostructures in the context of nanoscale storage media with ultrashort switching times. The goal of this collaborative effort between the Applied Optics group of Holger Schmidt (UC Santa Cruz, USA) and the Magnetic Nanostructures group of Manfred Albrecht (Chemnitz University of Technology, Germany) is to combine our unique capabilities for fabrication and characterization of patterned nanomagnetic materials to investigate a number of questions related to this novel material system:(a) We will for the first time demonstrate all-optical magnetization switching in single-domain nanomagnets using ferrimagnetic materials, here FeTb. We will investigate the dependence of this effect on the composition-dependent compensation point temperature in FeTb.(b) We will, for the first time, fabricate exchange-coupled FeTb-FePtCu heterostructures. FePtCu is attractive as magnetic storage material with adjustable magnetic anisotropy, Curie temperature, and crystallography. We will determine the dependence of the static magnetic properties of the FePtCu layers on the exchange coupling with FeTb.(c) We will demonstrate ultrafast switching of single FePtCu nanomagnets via exchange coupling from an all-optically controlled FeTb layer, thus combining the high-speed switching in a ferrimagnet with the hard magnetic storage capabilities of a ferromagnetic layer.(d) We will investigate the dependence of all-optical switching on two external parameters: (1) the three-dimensional shape of the nanomagnets by comparing curved nanomagnets with flat counterparts of the same size, and (2) the magnetic environment in a dense array using time resolved magneto-optic detection in the near field.This research is only enabled through the combination of the materials expertise of the Albrecht group and the single nanomagnet detection capabilities developed in the Schmidt group.