Layer thickness dependence of the current-induced effective field vector in Ta|CoFeB|MgO

• Published in: Nature materials 2013-03, Vol.12 (3), p.240-245
• Main Authors: Kim, Junyeon, Sinha, Jaivardhan, Hayashi, Masamitsu, Yamanouchi, Michihiko, Fukami, Shunsuke, Suzuki, Tetsuhiro, Mitani, Seiji, Ohno, Hideo
• Format: Article
• Language: English
• Subjects: 639/301/119/995; 639/301/119/997; Biomaterials; Condensed Matter Physics; Electric currents; Electronics; Heterostructures; Landscapes; Magnetic fields; Magnetism; Magnetization; Materials Science; Mathematical analysis; Nanotechnology; Optical and Electronic Materials; Orbits; Tantalum; Vectors (mathematics)
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat3522

Current-induced effective magnetic fields can provide efficient ways of electrically manipulating the magnetization of ultrathin magnetic heterostructures. Two effects, known as the Rashba spin orbit field and the spin Hall spin torque, have been reported to be responsible for the generation of the effective field. However, a quantitative understanding of the effective field, including its direction with respect to the current flow, is lacking. Here we describe vector measurements of the current-induced effective field in Ta|CoFeB|MgO heterostructrures. The effective field exhibits a significant dependence on the Ta and CoFeB layer thicknesses. In particular, a 1 nm thickness variation of the Ta layer can change the magnitude of the effective field by nearly two orders of magnitude. Moreover, its sign changes when the Ta layer thickness is reduced, indicating that there are two competing effects contributing to it. Our results illustrate that the presence of atomically thin metals can profoundly change the landscape for controlling magnetic moments in magnetic heterostructures electrically. The control and manipulation of the magnetization of thin metallic films by means of an electric current is a promising strategy for ensuring that potential spintronic applications are energy efficient. It is now shown that large changes in the current-induced magnetic field can arise as a result of varying the thickness of the Ta layer in Ta|CoFeB|MgO heterostructures.