Materials Science and Engineering B 126 (2006) 202–206 Quasi-static and dynamic switching of exchange biased micron-sized TMR junctions C. Maunoury a , C. Bilzer a,∗ , C.K. Lim b , T. Devolder a , J. Wecker c , L. B¨ ar c , C. Chappert a a Institut d’Electronique Fondamentale, UMR 8622 CNRS, Universit´ e Paris Sud Bˆ atiment 220, 91405 Orsay, France b HDD Program Team, Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, South Korea c Siemens AG, Corporate Technology MM 1,Paul-Gossen-Strasse 100, 91052 Erlangen, Germany Abstract We study the quasi-static and dynamical switching of magnetic tunnel junction patterned in micron-sized cells with integrated field pulse line. The tunnel junctions are CoFe/AlO/CoFe with an exchange biasing layer of MnIr. Quasi-static characterizations have been used to determine anisotropy, coercive as well as exchange bias fields. Dynamic switching measurements are done by applying fast-rising magnetic field pulses (178 ps–10 ns) along the hard axis of the junction with a quasi-static easy-axis applied field. We identify the field conditions leading to no-switching, to direct- writing and to toggle switching. We identify these field conditions up to the precessional limit, and construct the experimental dynamical astro¨ ıd. The magnetization trajectories leading to direct-writing and to toggle switching are well described by macrospin simulations. © 2005 Elsevier B.V. All rights reserved. Keywords: Precession; Switching; TMR junction; Toggle; Direct-write; Layered magnetic structures 1. Introduction The magnetic switching properties of micron-sized Tunnel- ing Magneto Resistance (TMR) junctions are currently attracting considerable interest thanks to their role in storage applications, in particular for magnetic random access memories (MRAM) [1]. MRAM are indeed good candidates for memory applica- tions thanks to their non-volatile and high density characters [1]. In magnetic tunnel junctions (MTJs), the information is stored in a magnetic “free layer”, i.e. a relatively soft magnetic layer with uniaxial in-plane anisotropy. The cell magnetization can be switched with orthogonal magnetic fields generated along the hard axis by the word line (field H y ) and along the easy axis by the bit line (H x ), either using Stoner–Wohlfarth switching [2] or using its precessional extensions [3]. The precessional switching [3–12] of magnetization is an energy-efficient way [6–9] to reverse the free layer magnetiza- tion and deserves thus to be studied. Precessional effects play an important role on time scales where the duration of the field pulse is comparable or shorter than the typical relaxation time of ∗ Corresponding author. Present address: Laboratoire d’Electronique et de Technologie de l’Information, CEA/LETI/DPTS, 17, av. des Martyrs, 38054 Grenoble Cedex 9, France. E-mail address: claus.bilzer@ief.u-psud.fr (C. Bilzer). magnetization. The specificity of precessional switching is that in contrast to the conventional longitudinal magnetic switching experiment, the field is applied at around 90 ◦ rather than 180 ◦ to the initial magnetization state. This field configuration allows to take advantage from the large precessional torque involved in the fundamental magnetization dynamics equation. In this paper, we investigate experimentally the magnetiza- tion switching in magnetic memory cells, in the precessional limit. Firstly, we detail the quasi-static properties of the mem- ory cells and then the magnetization trajectories by applying a fast-rising magnetic field pulse H y (178 ps–10 ns) along the hard axis of the junction with a quasi-static bit line field H x . The knowledge of {H x , H y , m x } parameters allows the construction of the experimental switching diagrams. We show that preces- sional toggle switching needs field pulses in the 200 ps range. Using macrospin simulations of some representative magneti- zation trajectories, we finally identify the area of no-switching, toggle switching, multiple toggle and direct-write switching for typical pairs of field parameters {H x , H y }. 2. Experimental An optical micrograph of an exchanged biased MTJ is shown in Fig. 1. The MTJ is patterned in an ellipse of lateral dimensions 1.58 m × 2.5 m. Its composition 0921-5107/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2005.09.027