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PGI Kolloquium:

Prof. Dr. Georg Schmidt,
Nanostrukturierte Materialien, Martin Luther Universität Halle-Wittenberg

PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

14.11.2014 11:00 Uhr

Tunneling anisotropic magnetoresistance and tunable tunnel barriers in organic spin valves

Magnetoresistance in organic spin valves is not necessarily based on electrical spin injection into the organic semiconductor and electrical detection of the spin polarized carriers. The demonstration of tunneling anisotropic magnetoresistance in [1] has shown that not even a second ferromagnetic electrode is necessary to create a spin valve effect if the first electrode exhibits the necessary magnetic anisotropy. Also recently it has been shown that in spin valves based on ALQ3 the total device resistance can be changed reproducibly by orders of magnitude applying voltages of several volts[2]. We have fabricated spin-valves which are based on La0.7Sr0.3MnO3 (LSMO), ALQ3, and a non-magnetic Cu counter electrode. These devices exhibit clear TAMR whose signature gives a perfect match to the magnetic anisotropy of the epitaxial LSMO layers. As in [2] we can tune the device resistance which goes along with a change in TAMR. For the high resistance state the TAMR can be as large as 17% at 4.2 K. I/V measurements show that the resistance change is due to the creation and modification of a tunnel barrier. Its influence on the TAMR clearly shows that the barrier is located at the interface between LSMO and ALQ3.

[1] M. Grünewald et al.: Tunneling anisotropic magnetoresistance in organic spin valves, Phys. Rev. B 84, 125208 (2011)
[2] M. Prezioso et al.: Electrically Programmable Magnetoresistance in Multifunctional Organic-Based Spin Valve Devices, Advanced materials 23, 1371 (2011)


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