时间：2020年7月27日14：00-15：30
地点：田家炳楼南205会议室
链接：https://meeting.tencent.com/s/9otd0NSFGMvL
会议 ID：425 710 271
邀请人：林维维
报告一：Development and characterization of magnetic thin film: Co/Pt
报告人：Sylvain Eimer（Université Paris-Saclay, CNRS; Fert Beijing Institute）
摘要：Magnetic properties Pt/Co/Pt trilayers make them essential elements in the industry of new magnetic memories. Here is a summary of the development of these thin films and the impact on perpendicular magnetic anisotropy. The Pt/Co/Pt trilayers were deposited by magnetron sputtering on different substrates, at different temperatures and varying the thickness of the different layers. The preliminary study shows the modification of the quality of these trilayers by irradiation and its impact on magnetic properties.
报告人简介：Sylvain Eimer is senior engineer of CNRS - Université Paris-Saclay. He is an expert on vacuum technology and magnetic materials.
报告二：Effects of interfacial interactions on optical switching in magnetic heterostructures
报告人：Pierre Vallobra（Fert Beijing Institute; Institut Jean Lamour, Université de Lorraine）
摘要：Since the evidence of the light induced demagnetization of Ni at the picosecond timescale in 1996 [1], ultrafast manipulation of the magnetization has been explored extensively. All optical switching (AOS) consists in reversing the magnetization with femtosecond pulses of circularly polarized light. It has been first demonstrated in GdFeCo alloys [2] and later in Co/Pt ferromagnetic layers [3]. In this talk I will focus on the role of the magnetic ordering temperatures (i.e. Curie temperature for ferromagnets and Néel temperature for antiferromagnets) on the optical modification of magnetic heterostructures. I will mainly describe the modification of the exchange bias field in a [Pt/Co]n/IrMn bilayer when we expose it to laser pulses of a femtosecond circularly polarized light. We demonstrate that the final exchange bias field after laser pulses results from the magnetic configuration of the [Pt/Co]n multilayer [4]. We will then briefly study the conditions required for a helicity-dependent all optical switching of a synthetic ferromagnetic material composed of CoFeB/Pt/CoFeB and Co ferromagnetic layers coupled antiferromagnetically [5] and conclude that the key factors that drives the switching of the total magnetization are the Curie temperatures of both layers.
[1] E. Beaurepaire, J.-C. Merle, A. Daunois and J.-Y. Bigot, Ultrafast Spin Dynamics in Ferromagnetic Nickel, Phys. Rev. Lett.76, 4250 (1996).
[2] C. Stanciu, F. Hansteen, A. Kimel, A. Kirilyuk, A. Tsukamoto, A. Itoh and T. Rasing, All-Optical Magnetic Recording with Circularly Polarized Light, Phys. Rev. Lett. 99, 047601 (2007).
[3] C.-H. Lambert, S. Mangin, B. Varaprasad, Y. Takahashi, M. Hehn, M. Cinchetti, G. Malinowski, K. Hono, Y. Fainman, M. Aeschlimann and E. Fullerton, All-optical control of ferromagnetic thin films and nanostructures, Science 345, 1337 (2014).
[4] P. Vallobra, T. Fache, L. Zhang, G. Malinowski, M. Hehn, J.-C. Rojas-Sánchez, E. Fullerton and S. Mangin, Manipulating exchange bias using all-optical helicity-dependent switching, Phys. Rev. B96, 144403 (2017).
[5] J.‐W. Liao, P. Vallobra, L. O'brien, U. Atxitia, V. Raposo, D. Petit, T. Vemulkar, G. Malinowski, M. Hehn, E. Martínez, S. Mangin, R. P. Cowburn, Controlling all-optical helicity-dependent switching in rare-earth free synthetic ferrimagnets, Advanced Science6, 1901876 (2019).
报告人简介：Pierre Vallobra received his PhD degree in Université de Lorraine in 2019. He is assistant researcher at Fert Beijing Institute in Beihang University.