INSTITUT DE PHYSIQUE ET CHIMIE DES MATERIAUX DE STRASBOURG
Département Magnétisme des Objets NanoStructurés
23, rue du Loess 67034 STRASBOURG Cedex 2
SEMINAIRE DMONS
Mardi 8 janvier 2013 à 11h00
à l'auditorium de l'IPCMS
Advancing in spintronics: Manipulation of Magnetic
Anisotropy and Enhancement of Spin Currents
Murat CUBUKCU
Laboratoire Nanostructures et Magnétisme, INAC, CEA/Grenoble
In the first part of my talk, I will focus on the magnetic anisotropy in thin ferromagnetic semiconductor
films. We have studied quaternary ferromagnetic GaMnAsP thin films. In these systems, we have
investigated how the magnetic anisotropies are influenced by the lattice mismatch induced biaxial strain
and the hole concentration. Two series of GaMnAsP layers characterized by different Mn concentrations
of 7% and 10% were investigated. For each series the P concentration has been varied over a wide range
from 0 to 20%. Of particular interest is the case of highly P doped layers where the conductivity regime
changes from metallic to impurity band conduction. This change induces a profound modification of all
pertinent magnetic parameters (Tc, Msat, uniaxial anisotropy) [1]. The variation of the four anisotropy
constants as a function of temperature and P has been determined. For intermediate P concentrations,
layers with zero uniaxial strain can be obtained [2]. The temperature induced magnetization
reorientations have been evidenced for 6% doped P [3]. The magnetization relaxation via the Gilbert
damping factor has been deduced from Ferromagnetic resonance (FMR) linewidth studies at two
different microwave frequencies [4].
In second part of my talk, I will present spin transport in metals and graphene- based lateral spin valves
(LSV). I will present the fabrication method using electron beam lithography and evaporation or
sputtering techniques. LSV consist of two ferromagnetic electrodes (FM) connected by a transverse non
magnetic spin channel where the transport properties are tuned by the magnetic states of the F
electrodes. In these structures, the charge and spin currents can be separated in order to rule out the
magneto-resistance effects of the electrodes and to avoid the presence of a background resistance
coming from the contacts [5]. We compared the spin signal amplitude measured on devices having the
FM layer in direct contact with the graphene or metal to the one obtained using tunnel contacts.
Although a sizeable spin signal can be obtained with direct contacts, the signal can be much enhanced
by inserting a high quality tunnel barrier [6-7]. Finaly, I will show spin injection in metallic and
semiconducting nanostructures by spin pumping generated by FMR [8].
[1] M. Cubukcu et al., Thin Solid Films, 519, 8212-8214 (2011) [2] M. Cubukcu et al., Phys. Rev. B (R) 81, 041202 (2010) [3] M. Cubukcu et al., Appl.
Phys. Lett. 96, 102502 (2010) [4] Kh. Khazen, M. Cubukcu et al. Phys. Rev. B, 78, 195210 (2008) [5] P. Laczkowski et al., Appl. Phys. Exp. 4, 063007
(2011) [6] J-C Sanchez, M. Cubukcu et al. (submitted) [7] M. Cubukcu et al. (in preparation) [8] A. Jain, M. Cubukcu et al., Phys. Rev. Lett., 109,
106603 (2012)
Pour tout contact : Bohdan KUNDYS (bohdan.kundys@ipcms.u-strasbg.fr)