First principles study of magnetoelectric coupling in Co₂FeAl/BaTiO₃ tunnel junctions

Abstract

Critical thickness for ferroelectricity and the magnetoelectric effect of Co2FeAl/BaTiO3 multiferroic tunnel junctions (MFTJs) are investigated using first-principles calculations. The ferroelectric polarization of the barriers can be maintained upto a critical thickness of 1.7 nm for both the Co2/TiO2 and FeAl/TiO2 interfaces. The magnetoelectric effect is derived from the difference in the magnetic moments on interfacial atoms, which is sensitive to the reversal of electric polarization. The magnetoelectric coupling is found to be dependent on the interfacial electronic hybridizations. Compared with the Co2/TiO2 interface, more net magnetization change is achieved at the FeAl/TiO2 interface. In addition, the in-plane strain effect shows that in-plane compressive strain can lead to the enhancement of ferroelectric polarization stability and intensity of magnetoelectric coupling. These findings suggest that Co2FeAl/BaTiO3 MFTJs could be utilized in the area of electrically controlled magnetism, especially the MFTJ with loaded in-plane compressive strain with the FeAl/TiO2 interface.

Electrodeposited Fe2CoSn Thin Film with Enhanced Structural and Magnetic Properties

“…The upper limit on U (=2.0 eV) was imposed to ensure that the corresponding magnetic moment evaluated was within realistic limit. 17 While there is no standard upper limit of U, it is generally restricted around 2.0, as reported by Kandpal et al, 18 (U Fe = 1.80 eV and U Co = 1.92 eV), Yu et al and Xu et al [19][20][21] (U Fe = 2.1 eV, and U Co = 2.2 eV) and Nia et al 22 (U Co = 1.92 eV).…”

Electric field tunable anisotropic magnetoresistance effect in an epitaxial Co2FeSi/BaTiO3 interfacial multiferroic system

“…So far, the FM/FE heterostructures consisting of Co-based Heusler alloys and BaTiO 3 have theoretically been examined by first-principles density functional calculations [23][24][25][26][27]. Since it is well known that the Co-based Heusler alloys such as Co 2 MnSi and Co 2 FeSi are half-metallic materials with high Curie temperatures [28][29][30], lots of spintronic applications have been explored in magnetic tunnel junctions [31,32] and semiconductor devices [33][34][35][36].…”

“…Since it is well known that the Co-based Heusler alloys such as Co 2 MnSi and Co 2 FeSi are half-metallic materials with high Curie temperatures [28][29][30], lots of spintronic applications have been explored in magnetic tunnel junctions [31,32] and semiconductor devices [33][34][35][36]. If these Co-based Heusler alloys are integrated with FE materials such as BaTiO 3 ,a n enhancement in the charge modulation effect is expected [23][24][25][26][27] because the inverse magnetoelectric-effect coefficient is proportional to the spin polarization of the FM materials. However, there is no report on experimental demonstration of the magnetoelectric effect in the interfacial multiferroic systems with Co-based Heusler alloys.…”

The large perpendicular magnetic anisotropy induced at the Co2FeAl/MgAl2O4 interface and tuned with the strain, voltage and charge doping by first principles study

“…Among all ferromagnetic materials, Co-based Heusler compound Co 2 FeAl (CFA) has been reported as an appropriate material which can induce a large interface PMA when bonded with MgO [19,25] or MgAl 2 O 4 [26,27] barriers. In addition, Co 2 FeAl is a half-metallic (HM) compound that can achieve quite high TMR since the spin polarization at the Fermi surface is 100% [28][29][30]. Nevertheless, some recent studies on the atomic distribution of CFA/MgO heterostructures have revealed that the Al atoms near the interface in CFA layer will diffuse into the MgO layer in large quantities, which may change the stoichiometric ratio of CFA layers and destroy the half-metallic property [26,[31][32][33].…”