Spin-polarized tunneling in MgO-based tunnel junctions with superconducting electrodes

Abstract

We prepared magnetic tunnel junctions with one ferromagnetic and one superconducting Al-Si electrode. Pure cobalt electrodes were compared with a Co-Fe-B alloy and the Heusler compound Co 2 FeAl. The polarization of the tunneling electrons was determined using the Maki-Fulde model and is discussed along with the spin-orbit scattering and the total pair-breaking parameters. The junctions were post-annealed at different temperatures to investigate the symmetry filtering mechanism responsible for the giant tunneling magnetoresistance ratios in Co-Fe-B/MgO/Co-Fe-B junctions. 3 5. Co-Fe-B-based junctions 4 6. Co 2 FeAl-based junctions 7 7. Summary 8 Acknowledgments 8 References 9

Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions

“…Non-collinear spin transport. The collinear spin transport calculation can provide a good description of the MR properties of conventional MTJs [4,35,60,66]. However, the noncollinear spin transport method must be employed when evaluating the performance of MTJs with perpendicular magnetic easy axes.…”

Low-field Switching Four-state Nonvolatile Memory Based on Multiferroic Tunnel Junctions

“…According to the above theory, when two ferromagnetic electrodes sandwiched with a thin layer of insulating material, a magnetic tunnel junction can be made. In our expectation, LSMO which had been tested as almost 100% positive spin-polarization and most of the ferromagnetic metals such as Co and Ni are negative 28 29 , so it can be assumed that our results of TMR would be negative.…”

“…The four-state non-volatile memory characteristic of this multiferroic tunnel junction was further demonstrated by the magnetic and electrical switching measurement 29 31 32 33 34 . During measurement, a device of NiFe/BTO/LSMO was placed in the middle of two current-controlled electromagnets with the magnetic field parallel to the film direction aiming to magnetize the NiFe and LSMO electrodes to the same direction.…”

“…This result suggests that the so-called four-state memory function can be realized by coupling and interplay between the magnetic and ferroelectric polarizations at this multiferroic tunneling structure. The magnetization direction dependent-resistance for this tunneling junction can be explained by tunneling magnetoresistance (TMR) which is about spin-polarized tunneling that involves alignment of magnetic moments of the two magnetic electrode layers 22 29 . According to Kouacou’s research in 2008 30 , LSMO/STO(001) has an easy magnetization direction with [110] as the easy-axis while along the perpendicular axis, the saturation field is much higher (the saturation field μ 0 H sat is found to be 7,000G at 285 K and 14,000G at 10 K), so there is no noticeable change in resistance because of the relatively much weaker magnetic field applied.…”