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MA: Fachverband Magnetismus
MA 55: Poster II
MA 55.57: Poster
Freitag, 4. April 2014, 10:30–13:30, P2
Vortex state free layer tunnelmagnetoresistance-sensors — •Frederick Casper1,2, Ronald Lehndorff3, Johannes Paul3, and Mathias Kläui2 — 1Johannes Gutenberg University, Institute for Inorganic and Analytical Chemistry, D-55099 Mainz, Germany — 2Johannes Gutenberg University, Institute for Physics, D-55099 Mainz, Germany — 3Sensitec GmbH, D-55131 Mainz, Germany
Within the last years magnetoresistive sensors based on the tunnel magneto resistance (TMR) effect have gained a great deal of attention for industrial application. One of their advantages compared to other magnetic sensors is a large signal amplitude, which allows for a reduction of read-out electronics. Here we present a concept for a vortex state free layer TMR sensor. These vortex states are used to linearize the output signal and also have a very narrow hysteresis. Therefore they seem to be ideal for position measurement application. The samples were made on a thermally oxidized 5” silicon wafer by dc magnetron sputtering using a conventional TMR stack: Ta/Ru seed /IrMn 8.9 nm/ CoFe 3 nm/ Ru 0.74 nm/ CoFeB 3.1 nm/ MgO X nm/ CoFeB 3.2 nm / NiFe 15 nm/ Ta cap. The films were annealed in an applied magnetic field of 10 kOe for 1h at 265∘C. Circular junctions with a diameter of 2 µm were formed using photo lithography. A sensor element compromises 20 of such junctions. The sensors show a large linear range of arond 10 Oe, a good thermal stability, a low hysteresis and a low area footprint, making them superior to conventional MR sensors.