Magnetostriction effect of amorphous CoFeB thin films and application in spin-dependent tunnel junctions

Abstract

CoFeB thin films and magnetic tunnel junctions using them are studied for magnetostriction effect. The single-layer films were sputter deposited with excellent soft magnetic properties including a high saturation magnetization of 1.5T, a near-zero hard axis coercivity, a low easy axis coercivity of 2.0Oe, and an induced magnetic anisotropy field of 32Oe. The saturation magnetostriction constant is measured to be 31ppm. Magnetic tunnel junctions (MTJs) were fabricated and tested for potential strain gauge applications. The gauge factor for the magnetostrictive MTJs, a measure of strain sensitivity, is many times of the best piezoresistive devices.