Byungro Kim

Current-induced field-free magnetic switching using spin–orbit torque has been an important topic for decades due to both academic and industrial interest. Most research has focused on introducing symmetry breakers, such as geometrical and compositional variation, pinned layers, and symmetry-broken crystal structures, which add complexity to the magnetic structure and fabrication process. We designed a relatively simple magnetic structure, composed of a [Co/Pt] multilayer and a Co layer with perpendicular and in-plane magnetic anisotropy, respectively, with a Cu layer between them. Current-induced deterministic magnetic switching was observed in this magnetic system. The system is advantageous due to its easy control of the parameters to achieve the optimal condition for magnetic switching. The balance between magnetic anisotropic strength and interlayer coupling strength is found to provide the optimal condition. This simple design and easy adjustability open various possibilities for magnetic structures in spin-based electronics applications using spin–orbit torque.

Current-induced field-free magnetic switching using spin-orbit torque has been an important topic for decades due to both academic and industrial interest. Most research has focused on introducing symmetry breakers, such as geometrical and compositional variation, pinned layer, and symmetry-broken crystal structures, which add complexity to the magnetic structure and fabrication process. We designed relatively simple magnetic structure, composed of a [Co/Pt] multilayer and a Co layer with perpendicular and in-plane magnetic anisotropy, respectively, with a Cu layer between them. Current-induced deterministic magnetic switching was observed in this magnetic system. The system is advantageous for its easy control of the parameters to achieve the optimal condition for magnetic switching. The balance between magnetic anisotropic strength and interlayer coupling strength is found to provide the optimal condition. This simple design and easy adjustability opens various possibilities for magnetic structures in spin-based electronics applications using spin-orbit torque.

A magnetic nanostructure for auto-oscillation, induced by spin-transfer torque, is fabricated by cosputtering permalloy with cobalt. Although the system does not meet the critical size and current requirements for direct auto-oscillation, magnetic signals resulting from spin wave excitation and magnetic fluctuations are measured by a Brillouin light scattering (BLS) system. From the analysis of the BLS spectrum, the threshold current for auto-oscillation is estimated to be 27.3% lower in Py_1−xCo_x (x = 0.2095) than in Py_1−xCo_x (x = 0.0). It is surmised that the cobalt in permalloy improves the efficiency of transferring spin toque for auto-oscillation.

A magnetic nanostructure for auto-oscillation, induced by spin-transfer torque, is fabricated by cosputtering permalloy with cobalt. Although the system does not meet the critical size and current requirements for direct auto-oscillation, magnetic signals resulting from spin wave excitation and magnetic fluctuations are measured by a Brillouin light scattering (BLS) system. From the analysis of the BLS spectrum, the threshold current for auto-oscillation was estimated to be 27.3% lower in Py 1- x Co x ( x = 0.2095) than in Py 1- x Co x ( x = 0.0). It is surmised that the cobalt in permalloy improves the efficiency of transferring spin toque for auto-oscillation.

The characteristics of parametric spin-wave pumping are investigated in three rectangular permalloy blocks with in-plane aspect ratios of 12, 6, and 4. Micro-Brillouin light scattering (BLS) spectroscopy is utilized to detect the intrinsic properties of excited spin waves under various excitation conditions of an external magnetic field and microwave power. Based on the theoretical dispersion relation and BLS intensity and its spatial profile, the parametric spin wave with a frequency of f sw = 5 .6 GHz is found to be excited in fundamental mode in a block of largest aspect ratio while the other block have higher-order or edge-localized modes along the width direction. The data shows that the nature of spin waves is quite sensitive on the conditions of sample geometry, applied field and microwave power. Thus, with the appropriate combination of the three parameters, it would be possible to control the nature of spin wave in each block simultaneously, which increase the blocks’ potential in magnonic applications, such as spin-logic and interferometer.