Spin polarized carriers electrically injected into a magnet from an external polarizer can exert a spin transfer torque (STT) 1 on the magnetization. The phenomenon belongs to the area of spintronics research focusing on manipulating magnetic moments by electric fields and is the basis of the emerging technologies for scalable magnetoresistive random access memories.2 In our previous work we have reported experimental observation 3 of the optical counterpart of STT 4,5 in which a circularly polarized pump laser pulse acts as the external polarizer, allowing to study and utilize the phenomenon on several orders of magnitude shorter timescales than in the electric current induced STT. Recently it has been theoretically proposed [6][7][8] and experimentally demonstrated 9-11 that in the absence of an external polarizer, carriers in a magnet under applied electric field can develop a non-equilibrium spin polarization due to the relativistic spin-orbit coupling, resulting in a current induced spin-orbit torque (SOT) acting on the magnetization. In this paper we report the observation of the optical counterpart of SOT. At picosecond time-scales, we detect excitations of magnetization of a ferromagnetic semiconductor (Ga,Mn)As which are independent of the polarization of the pump laser pulses and are induced by non-equilibrium spin-orbit coupled photo-holes.In current induced STT, spin-polarized carriers are electrically injected into a magnetic object, such as thin ferromagnetic layer or domain wall, from another part of a non-uniform magnetic structure. The physical origin of STT is in the angular momentum transfer from the injected carrier spins to the magnetic moments. The current induced SOT, on the other hand, is observed in uniform magnets with no external source of spin polarized carriers. The non-equilibrium spin polarization of carriers producing SOT results from current induced redistribution of carrier states in the band structure of the magnet. The physical origin of SOT is the spin-orbit coupling in the carrier bands. While the seminal works on current induced STT are more than 15 years old 12,13 and the effect already plays a key role in commercially developed spintronic technologies, the research of the relativistic SOT is still at its infancy. Yet, the remarkable property of this inverse magneto-transport effect, allowing a single piece of magnet to excite itself under applied electric field, has already found practical utility. For example, when combined with the self-detection of the magnetization variations by anisotropic magnetoresistance, which is a direct magneto-transport effect based also on 2 spin-orbit coupling, an all-electric ferromagnetic resonance measurement of micromagnetic parameters can be performed on a single ferromagnetic nanostructure. 11The aim of our works reported in Ref. In the optical spin transfer torque (OSTT), observed in our previous experiments inRef. 3, the external source for injecting spin polarized carriers is provided by circularly polarized light at normal incide...

Magnetic properties are commonly used to identify new aromatic molecules because it is generally believed that magnetization and energetic stability are correlated. To verify the potential correlation between the energy and magnetic response properties, we examined a set of 198 isomers of C H . The energy and magnetic properties of these molecules can be directly compared with no need to invoke any arbitrary reference state because the studied systems are all isomers. Benzene is the global minimum on the potential energy surface of C H , 35 kcal mol lower in energy than the second most stable isomer, fulvene. Unlike its electronic energy, isotropic magnetizability of benzene is slightly lower than the average magnetizability of its isomers. Altogether, 44 isomers of C H were identified to have more negative magnetic susceptibility than benzene but were between 67.0 to 168.6 kcal mol higher in energy than benzene. However, benzene is unique in two ways. Analyzing the paramagnetic contribution to the magnetic susceptibility as originally suggested by Bilde and Hansen (Mol. Phys., 1997, 92, 237) revealed that 53 molecules have lower paramagnetic susceptibility than benzene but among monocyclic systems benzene has the least paramagnetic susceptibility. Furthermore, benzene has the largest out-of-plane magnetic susceptibility that originates from the strongest ring current among all studied species.

Spin-valves or spin-transistors in magnetic memories and logic elements are examples of structures whose functionality depends crucially on the length and time-scales at which spin-information is transferred through the device. In our work we employ spatially resolved optical pump-and-probe technique to investigate these fundamental spin-transport parameters in a model semiconductor system. We demonstrate that in an undoped GaAs/AlGaAs layer, spins are detected at distances reaching more than ten microns at times as short as nanoseconds. We have achieved this unprecedented combination of long-range and high-speed electronic spin-transport by simultaneously suppressing mechanisms that limit the spin life-time and the mobility of carriers. By exploring a series of structures we demonstrate that the GaAs/AlGaAs interface can provide superior spin-transport characteristics whether deposited directly on the substrate or embedded in complex semiconductor heterostructures. We confirm our conclusions by complementing the optical experiments with dc and terahertz photo-conductivity measurements.

Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinarily difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representatives of this class of materials—Mn3Sn. We demonstrate that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well-defined domain pattern at room temperature based on heat assisted recording principle. Our study opens up a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution.