No abstract

Spin structures of an exchange-coupled-bilayer system of expanded-face-centered-tetragonal (e-fct) Mn(001) ultrathin films grown on Co/Cu(001) were resolved by means of spin-polarized scanning-tunneling microscopy. With an in-plane spin-sensitive probe, a layered antiferromagnetic-spin ordering of Mn overlayers was evidenced directly. In addition, the spin frustration across the same Mn layer creating a narrow domain wall down to nanometer scale was also observed along the buried step of Co underlayers. According to the micromagnetic simulation, the step-induced domain-wall width is in agreement with the experimental results. Such in-plane layered antiferromagnetic-spin structures of e-fct Mn(001) provide uncompensated spins at the interface with Co underlayers and elucidate the mechanism of the corresponding exchange-bias field observed in the previous studies.

Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al2O3∕NiAl(100). At 140–170K, a slow deposition rate (0.027ML∕min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼260∕104nm2 even after 800–1090K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials.

It has been shown that W in its resistive form possesses the largest spin-Hall ratio among all heavy transition metals, which makes it a good candidate for generating efficient dampinglike spin-orbit torque (DL-SOT) acting upon adjacent ferromagnetic or ferrimagnetic (FM) layer. Here we provide a systematic study on the spin transport properties of W/FM magnetic heterostructures with the FM layer being ferromagnetic Co 20 Fe 60 B 20 or ferrimagnetic Co 63 Tb 37 with perpendicular magnetic anisotropy. The DL-SOT efficiency DL ξ , which is characterized by a current-induced hysteresis loop shift method, is found to be correlated to the microstructure of W buffer layer in both W/Co 20 Fe 60 B 20 and W/Co 63 Tb 37 systems. Maximum values of 0.144 DL ξ ≈ and 0.116 DL ξ ≈ are achieved when the W layer is partially amorphous in the W/Co 20 Fe 60 B 20 and W/Co 63 Tb 37 heterostructures, respectively. Our results suggest that the spin Hall effect from resistive phase of W can be utilized to effectively control both ferromagnetic and ferrimagnetic layers through a DL-SOT mechanism. † / 2 s S He J e T J θ = h , where TM SH θ is the internal spin Hall ratio of the TM layer and TM e J represents the longitudinal charge current density flowing in the TM layer. TM/FM int T represents the spin transparency at the TM/FM interface [12,13] (note that TM/FM int 1 T = for a perfect transmission), which is related to the spin-mixing conductance [14,15]. The transmitted spin angular momentum from s J can be transferred to the magnetic moments in FM through a spin-transfer torque mechanism [16]. The final effect is therefore a dampinglike spin-orbit torque (DL-SOT) acting upon the FM layer, and the DL-SOT efficiency of a TM/FM bilayer heterostructure can be expressed as

Self-assembled one-dimensional nanostripes on the single-crystalline Al2O3 domains are found to be the nucleation sites of nanoparticles through an enhanced density of states observed by the scanning tunneling microscopy and spectroscopy. Bias-dependent topographic images and the conductivity spectra indicate that these nanostripes have both enhanced occupied and unoccupied states within the oxide bandgap. These more metallic nanostripes have stronger electronically trapping ability than the oxide domain, which can be used as a one-dimensional electronically self-patterned template for the guided growth of nanostructures.