High energy magnons in ultrathin ferromagnets: Spin-polarized electron energy loss spectroscopy stud

发布时间:2015-05-13    作者:    来源:    浏览次数:4258    打印

报告题目:High energy magnons in ultrathin ferromagnets: Spin-polarized electron energy loss spectroscopy study

报  告 人:秦华军  博士 ( 芬兰阿尔托大学)

报告时间:2015 年 05 月 20 日(周三)下午 15:00-16:00

报告地点:南校区双超所 211 会议室 



Abstract: Elementary magnetic excitations (magnons) are essential for understanding many fundamental magnetic properties and technological applications in magnon-based devices, ultrahigh-density magnetic recording, magnetic tunneling junctions, and so on. To probe high energy magnons, spin-polarized electron energy loss spectroscopy (SPEELS) is a powerful tool due to the capability of measuring magnons over the whole surface Brillouin zone and the capability of investigating spin-dependent scattering.


  In this talk, the concept of magnons, SPEEL-spectrometer, and the mechanism of magnon excitations are introduced firstly. The magnon measurements in ultrathin FePd alloy films grown on Pd(001) are then presented. It is observed that the magnons’ energy can be largely tuned by varying Fe concentration.  And the magnons’ lifetime in ultrathin FePd alloy films is rather long compared to the one in Fe films grown on other substrates. First-principles calculations revealed that the long magnons’ lifetime has its origin in the peculiar electronic hybridizations between Fe and Pd atoms. These electronic hybridizations lead to the suppression of the relaxation channels of high energy magnons and result in a long magnons’ lifetime. Finally, the temperature dependence of such long-lived magnons is also presented. Up to 400 K (1.2 Curie temperature), the magnons are still efficiently excited. The renormalization of magnons’ energy and lifetime as a function of temperature is observed, but weaker than that reported.