title: Tunnel Magnetoresistance Sensors with Magnetostrictive Electrodes: Strain Sensors.
abstract: Magnetostrictive tunnel magnetoresistance (TMR) sensors pose a bright perspective in micro- and nano-scale strain sensing technology. The behavior of TMR sensors under mechanical stress as well as their sensitivity to the applied stress depends on the magnetization configuration of magnetic tunnel junctions (MTJ)s with respect to the stress axis. Here, we propose a configuration resulting in an inverse effect on the tunnel resistance by tensile and compressive stresses. Numerical simulations, based on a modified Stoner-Wohlfarth (SW) model, are performed in order to understand the magnetization reversal of the sense layer and to find out the optimum bias magnetic field required for high strain sensitivity. At a bias field of -3.2 kA/m under a 0.2 × 10 - 3 strain, gauge factors of 2294 and -311 are calculated under tensile and compressive stresses, respectively. Modeling results are investigated experimentally on a round junction with a diameter of 30 ± 0.2 μ m using a four-point bending apparatus. The measured field and strain loops exhibit nearly the same trends as the calculated ones. Also, the gauge factors are in the same range. The junction exhibits gauge factors of 2150 ± 30 and -260 for tensile and compressive stresses, respectively, under a -3.2 kA/m bias magnetic field. The agreement of the experimental and modeling results approves the proposed configuration for high sensitivity and ability to detect both tensile and compressive stresses by a single TMR sensor.
authors.affiliation: Institute for Materials Science, Kiel University, Kaiserstrasse 2, 24143 Kiel, Germany. ata@tf.uni-kiel.de.
authors.forename: Ali
authors.initials: A
authors.lastname: Tavassolizadeh
authors.affiliation: Department of Physics, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany. rott@physik.uni-bielefeld.de.
authors.forename: Karsten
authors.initials: K
authors.lastname: Rott
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. meier_tobias@email.gwu.edu.
authors.forename: Tobias
authors.initials: T
authors.lastname: Meier
authors.affiliation: Institute for Materials Science, Kiel University, Kaiserstrasse 2, 24143 Kiel, Germany. eq@tf.uni-kiel.de.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Quandt
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. hendrik.hoelscher@kit.edu.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Hölscher
authors.affiliation: Department of Physics, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany. reiss@physik.uni-bielefeld.de.
authors.forename: Günter
authors.initials: G
authors.lastname: Reiss
authors.affiliation: Institute for Materials Science, Kiel University, Kaiserstrasse 2, 24143 Kiel, Germany. dm@tf.uni-kiel.de.
authors.forename: Dirk
authors.initials: D
authors.lastname: Meyners
keywords: inverse magnetostriction; strain sensors; tunnel magnetoresistance