title: Effect of Low-Frequency AC Magnetic Susceptibility and Magnetic Properties of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions.
abstract: In this investigation, the low-frequency alternate-current (AC) magnetic susceptibility (χac) and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ) determined coercivity (Hc) and magnetization (Ms) and correlated that with χacmaxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χacand maximum phase angle (θmax) at the optimal resonance frequency (fres), at which the spin sensitivity is maximal. The results reveal that χacfalls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χacis at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χacand maximum phase angle. The corresponding maximum of χacis related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χacstrength.
authors.affiliation: Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan. ytchen@isu.edu.tw.
authors.forename: Yuan-Tsung
authors.initials: YT
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan. isu10107009m@cloud.isu.edu.tw.
authors.forename: Sung-Hao
authors.initials: SH
authors.lastname: Lin
authors.affiliation: Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan. sheu415@isu.edu.tw.
authors.forename: Tzer-Shin
authors.initials: TS
authors.lastname: Sheu
keywords: exchange coupling; low-frequency alternate-current (AC) magnetic susceptibility (χac); magnetic tunnel junctions (MTJs); resonance frequency (fres)