Tunneling Anisotropic Magnetoresistance in Co/AlO_x/Au Tunnel Junctions

Abstract

We observe spin-valve-like effects in nano-scaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.Comment: 11 pages, 5 figures. Accpted for publishing on Nano Letters, 200

Angular dependence of the tunneling anisotropic magnetoresistance in magnetic tunnel junctions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] This diversity has made it difficult to build a unified theory of the TAMR. In fact, although there exists a general consensus in identifying the spin-orbit coupling ͑SOC͒ as the mechanism responsible for the TAMR, it has been recognized that the way the SOC influences the TAMR may depend on the considered system and configuration.…”

Magnetoresistance studies on Co∕AlOX∕Au and Co∕AlOX∕Ni∕Au tunnel structures

“…Recently, a spin valve-like effect known as TAMR was reported in tunnel structures with only one magnetic electrode. [5][6][7] These results emphasize the importance of clarifying the origin of tunneling MR ͑TMR͒-like signals in F/N/F experiments. In this work, we present a comparative MR study of Co/ AlO X / Au and Co/ AlO X / Ni/ Au tunnel junctions where very different MR behaviors are observed and interpreted in terms of different physical mechanisms.…”

“…The sign of the MR for the former case is negative, while it is positive for the latter one because of the magnetization-dependent tunneling DOS in Co electrodes. 7 In contrast, this anisotropic MR phenomenon is not observed in the Co/ AlO X / Ni tunneling junction, as shown in Figs. 3͑c͒ and 3͑d͒, where both sweep directions display a positive MR.…”

“…2͑a͒ and 2͑b͒ is not due to injection and detection of spin-polarized current via the central Au island, but rather to a magnetization-dependent tunneling density of states ͑DOS͒ in the Co electrodes induced by spin-orbit ͑s-o͒ interaction. 7 The MR signals in Figs. 2͑c͒ and 2͑d͒, however, follow the conventional TMR phenomenology in MTJs 9 and can be ascribed to the tunneling spin polarization of the Co electrode and the Ni layer, modified by the insulating barrier.…”

Microscopic mechanism of leakage currents in silica junctions

“…Many new physics appear in nanoscale capacitor due to the coupling effects of insulating barriers and the electrodes. 19,20 In order to understand the microscopic origin of the detrimental trapping defects, the large leakage current, and their influence on dielectric breakdown process, we combine nonequilibrium Green's function technique with density functional theory ͑DFT͒ to provide a physical analysis of the leakage current in the atomic scenario. The effects of interface structure, external stress, and defect trapping on electronic transport properties for the Al-SiO 2 -Al two-probe systems are reported in this study.…”