Effects of annealing and MgO thickness on perpendicular magnetic anisotropy in Pt/Co₂FeAl_0.5Si_0.5/MgO/Pt multilayers

Abstract

Phone/Fax: þ86 10 62333209Magnetic properties have been studied for Ta/Pt/Co 2 FeAl 0.5 Si 0.5 (CFAS)/MgO/Pt multilayers to investigate the effects of annealing and MgO thickness on perpendicular magnetic anisotropy (PMA). We show that PMA is very sensitive to the annealing conditions and MgO thickness. Strong PMA with high remanence ratio can be achieved after annealing at 300 8C for just 10 min. The thickness of CFAS (t CFAS ) with PMA is strongly dependent on the MgO thickness (t MgO ). A large t CFAS with PMA is observed to be 4.8 nm for t MgO ¼ 1.6 nm. The saturation magnetization (M s ) decreases on increasing t MgO with an obviously periodic oscillation, and the periods of oscillation are between 0.2 and 0.3 nm. Moreover, the annealed structure shows good thermal stability and a weaker temperature dependence of the squareness ratio (M r /M s ) for the samples with thicker MgO.

Perpendicular magnetic anisotropy of Pt/Co2FeAl0.5Si0.5/MgAl2O4 trilayers

“…It is similar to the Pt/Co (or CoFeB)/MgO structure in which there is also a transition from IMA to PMA after annealing due to the oxidation of Co (or CoFeB). The PMA of Pt (5 nm)/CFAS (1.5 nm)/MAO (0.9 nm) is stable even after annealing at 400 °C, which is comparable to that of Pt/CFAS/MgO structure . Further increasing T a to 450 °C, the easy magnetic axis gets back to in‐plane again, and the PMA disappears.…”

“…The annealing procedure includes three steps as follow: firstly, the center area of quartz‐glass tube was heated to given temperatures in vacuum with a heating rate of 10 °C min −1 ; secondly, the samples were rapidly pushed into the center of quartz‐glass tube and annealed for 30 min; finally, the samples were pulled out of the heated area and naturally cooled to room temperature in vacuum without external magnetic field. The crystal structure of CFAS has been studied by grazing incidence X‐ray diffraction under the same fabrication conditions in our previous work . It was demonstrated that the as‐deposited CFAS films are crystallized in disordered A2 phase.…”

“…Unlike MgO, MAO is a chemically stable and non‐deliquescent oxide, which is suitable for wet processes during device micro‐fabrication. Moreover, it has a small lattice mismatch of about 1% with Co‐based Heusler alloys (e.g., Co 2 FeSi and Co 2 FeAl), in which great efforts have been put to realize the PMA by controlling interfacial oxidation with MgO barrier, such as Co 2 FeAl/MgO , Co 2 FeSi/MgO , Co 2 FeAl 0.5 Si 0.5 (CFAS)/MgO , and Co 2 Fe x Mn 1− x Si (CFMS)/MgO .…”

Robust Perpendicular Magnetic Anisotropy in MgO/Co2FeAl/MgO Stacks Induced by MgO over Layer and Annealing Temperature

“…IPA and PMA originate from the shape anisotropy and interface anisotropy of the films. Hence, recent research has been mainly concentrated on fabricating multilayer films with PMA property . In this study, we have put effort to achieve the strong PMA property of CFA film on MgO buffer layer by varying the MgO film thickness and annealing temperature for p‐MTJs‐based spintronic devices.…”

“…In addition, a promising oxide layer of MgO has a good lattice match with Co 2 FeAl (CFA) films and the interface between CFA and MgO could strongly induce the PMA property. The presence of PMA is widely originated from the Co/Fe‐3d and O‐2p orbitals hybridization at FM/(MgO or MgAl 2 O 4 ) interface with suitable buffer layers . Recently, CFA is found to display the PMA property with different buffer layer systems such as Pt/CFA/MgO, Cr/CFA/MgO, Ta/CFA/MgO, and Ta/Pd/CFA/Ta layers .…”