Perpendicular magnetic anisotropy in Pt/Co-based full Heusler alloy/MgO thin-film structures

Abstract

Perpendicular magnetic anisotropy (PMA) in ultrathin magnetic structures is a key ingredient for the development of electrically controlled spintronic devices. Due to their relatively large spin-polarization, high Curie temperature and low Gilbert damping the Co-based full Heusler alloys are of special importance from a scientific and applications point of view. Here, we study the mechanisms responsible for the PMA in Pt/Co-based full Heusler alloy/MgO thin films structures. We show that the ultrathin Heusler films exhibit strong PMA even in the absence of magnetic annealing. By means of ferromagnetic resonance experiments, we demonstrate that the effective magnetization shows a two-regime behavior depending on the thickness of the Heusler layers. Using Auger spectroscopy measurements, we evidence interdiffusion at the underlayer/Heusler interface and the formation of an interfacial CoFe-rich layer which causes the two-regime behavior. In the case of the ultrathin films, the interfacial CoFe-rich layer promotes the strong PMA through the electronic hybridization of the metal alloy and oxygen orbitals across the ferromagnet/MgO interface. In addition, the interfacial CoFe-rich layer it is also generating an increase of the Gilbert damping for the ultrathin films beyond the spin-pumping effect. Our results illustrate that the strong PMA is not an intrinsic property of the Heusler/MgO interface but it is actively influenced by the interdiffusion, which can be tuned by a proper choice of the underlayer material, as we show for the case of the Pt, Ta and Cr underlayers. a) mihai.gabor@phys.utcluj.ro

Shaping Perpendicular Magnetic Anisotropy of Co2MnGa Heusler Alloy Using Ion Irradiation for Magnetic Sensor Applications

“…This is depicted in Figure 6b as the decrease in the peak atomic concentrations of Mg, O, Co, Mn, Ga and Pd, relative to the un-irradiated stack, with increasing Ar fluence. In a recent report, Gabor et al [111] studied CoFe-based Heusler alloys and found that a CoFe-rich interfacial layer promotes strong electronic hybridization between the metal and oxygen orbitals, leading to PMA. Similarly, Sun et al [62] studied the effects of buffer layers such as Pd, Ru and Cr in the formation of PMA in Co2Fe0.4Mn0.6Si Heusler alloy films.…”

Magnetoelastic interactions and magnetic damping in Co2Fe0.4Mn0.6Si and Co2FeGa0.5Ge0.5 Heusler alloys thin films for spintronic applications

“…The importance of a non-Gilbert-damping mechanism in such Heusler materials was studied in the paper 61 , indicating particular importance of the intrinsic two-magnon scattering mechanism. Strong perpendicular magnetic anisotropy was recently observed in ultrathin (below 2 nm) Co 2 YZ Heusler thin-film structures 62 – 65 , what was explained by the formation of a CoFe ordered alloy at the interface, which also caused an increase of the Gilbert damping parameter.…”

Giant unilateral electric-field control of magnetic anisotropy in MgO/Rh2CoSb heterojunctions

“…It was reported in experiments that the critical thickness for the Heusler alloys to maintain out-of-plane MA in MgO-based magnetic heterojunctions was around 1 nm. [50][51][52] Thus, here, we choose the heterojunctions with seven layers of Rh 2 CoSb (B1.05 nm). The thickness of MgO in all the calculations is chosen to be five layers, as the test calculation shows that a MgO slab with more than three layers has no effect on the MA.…”