[19a-331-7~12] 10.3 Spin devices, magnetic memories and storages

▼ [19a-331-9] Sensitivity improvement of a strain direction sensor using an exchange bias

〇Hiroki Matsumoto¹, Shinya Ota¹, Akira Ando², Tomohiro Koyama¹, Daichi Chiba¹ (1.Univ. of Tokyo, 2.Murata Manufacturing Co., Ltd.)

Keywords:GMR, strain sensor, exchange bias

A magnetization of a ferromagnetic thin film deposited on a flexible substrate can be controlled by an application of tensile strain . Based on this, we have recently demonstrated a strain direction sensing using a Co/Cu/Py giant magnetoresistive (GMR) device formed on a flexible substrate . In this structure, the relative angle of magnetizations between the strain-sensitive Co free layer and strain-insensitive Py pinned layer depends on the strain direction, which can be detected from the modulation of device resistance R through the GMR effect. More than 1% of strain, however, has been needed to detect accurately the strain direction because of a necessity of an auxiliary field H_a for retaining the strain-insensitive Py layer a single domain state. H_a even disturbs the strain-induced free rotation of the strain-sensitive Co magnetization, and thus, has caused the low sensitivity. In this work, we develop a strain direction sensor that enables an H_a-free operation by use of an exchange bias (EB) which is effective only to the Py layer.