Until two years ago, the smallest permanent magnets were single molecule magnets. Surface Science has opened up an alternative approach to this field in studying the magnetic properties of single atoms adsorbed onto surfaces. Very recently a major breakthrough was achieved by identifying systems where a single surface adsorbed atom are stable magnets. Ho atoms on two monolayer thick MgO(100)...
Reliable organic spintronic devices depend on spin-injecting interfaces with precisely architectured multilayers to avoid premature failure e.g. due to current filaments building up at defects. Using X-ray Magnetic Circular Dichroism (XMCD) we present unambiguous evidence that in the sequential fabrication of organic bilayer interfaces by physical vapor deposition (sublimation), molecules...
The properties of antiferromagnetic materials at the nanoscale are important for future spintronic devices. We study the magnetic properties of goethite at the nanoscale by combining X-ray linear dichroism (XLD) spectroscopy and X-ray photoemission electron microscopy. Complementary scanning electron microscopy is used to correlate the magnetic properties of individual goethite nanoparticles...
Correlated electron systems display electronically ordered ground states often intrinsically segregated at the nano/mesoscale. Antiferromagnetic order is a common instability of these materials potentially showing spatial inhomogeneity. I will present our recent result using a resonant soft X-ray scattering nanoprobe to image the bulk magnetic landscape in NdNiO3 thin films. Our measurements...
The magnetic reversal in perpendicular exchange-coupled systems consisting of a rare earth-based ferrimagnet (amorphous TbFe) and a transition metal-based ferromagnet (crystalline Co/Pt), can be surprisingly complex and different from conventional systems. We address the reversal mechanism locally by high-resolution MFM at 10K and in high fields. The TbFe layer alone reveals no change in its...
Understanding and controlling the damping in ferromagnetic thin films is very important for emerging technologies including magnonics and spintronics. One of the possible ways to manipulate magnetic damping is injection of spin current generated due to spin Hall effect [1]. To measure the modulation of damping we use a time-resolved magneto-optical Kerr effect microscope (TR-MOKE), which has...
SrRuO3-SrIrO3 bilayers have recently attracted attention due to their topological Hall effect (THE) as an evidence of interfacial Dzyaloshinskii–Moriya interaction (DMI), which may lead to the formation of skyrmion phase. We measured THE in a SRO-SIO bilayer at different temperatures between 5K and 100K, and performed MFM in external fields. We observe maze pattern of...
Current-induced spin orbit torques are well established as a powerful method to manipulate magnetic thin films, with latest works demonstrating magnetization reversal down to the sub-ns scale. The reversal mechanism is a two-step process determined by domain wall nucleation and propagation. Recent work indicates that the domain nucleation process is a bottleneck for energy efficient switching....
Zigzag graphene nanoribbons (ZGNRs) have attracted considerable interest due to the unique edge states they host. We recently established an on-surface synthesis approach to synthesize atomically precise 6-ZGNRs using a carefully designed precursor monomer. Furthermore, our recent experiments on exfoliated graphene nano-constrictions provide the first evidence through ballistic electron...
The textbook magnetic domain wall is a very simple object: Its shape and width are described by a few material properties only. In nanostructures, however, the situation is different. By high-resolution imaging we observe complex spin arrangements that strongly deviate from those commonly encountered in magnetic films or bulk ferromagnets, for in-plane as well as perpendicularly magnetized...
In this work, we study how oscillator synchronization can be used to optimize the domain wall (DW) dynamics in magnetic bilayers with perpendicular anisotropy. We show that dipolarly coupled DWs reach larger velocities as compared to isolated walls when the two chiral walls form a magnetic flux closing object. While this situation is easily maintained in a stationary motion regime, the...
The emerging interfacial Dzyaloshinskii-Moriya interaction (iDMI) can lead to fast current-driven domain wall motion and the formation of topological magnetic skyrmions, which is promising for the design of high performance spintronic devices. Here, a nanometric island of Pt/Co/AlOx (Al) was fabricated with patterned regions of varying out-of-plane and in-plane magnetic anisotropies. We...
Recently, current-induced spin-orbit torques(SOT) switching have been demonstrated in ferromagnet(FM) / antiferromagnet(AFM) multilayers with perpendicular anisotropy [1,2]. The use of an AFM results in multiple nonvolatile (memristive) states, akin to neural networks [3]. Past experiments suggest that the non-uniform exchange bias from the AFM causes separate switching of domains, leading to...
We investigated the correlation between structure, oxidation, and magnetic properties of Pt/Co/AlOx heterostructures deposited by magnetron sputtering. We find that the magnetic anisotropy and the spin-orbit torques are both affected by the degree of oxidation of the Co/Al interface. Moreover, we find that oxidation also influences the domain texture and the current-induced...
Artificial spin ices are composed of geometrically frustrated arrangements of lithographically patterned single-domain nanomagnets. We have fabricated a spin ice based active material, a chiral ice, which converts energy into unidirectional dynamics, thus functioning like a ratchet [1] and demonstrating the potential of spin ices to build functional materials. Measurements combining...
Topological defects in kagome artificial spin ice (KASI)—arrays of interconnected nanomagnets on kagome lattice—appear in the form of monopole-antimonopole pairs and Dirac strings in the switching regime. Experimental determination of spin-precession frequencies of nanobars confined by topological defects has been elusive so far. However their understanding is key towards utilization of KASI...
The Nitrogen-Vacancy (NV) defect center is a stable, atomic-scale defect containing a single electron spin, which, when integrated into the tip of an atomic force microscope, enables high resolution, quantitative magnetic imaging. Here, we present NV magnetic field imaging and relaxometry to probe static magnetization and GHz spin dynamics in artificial kagome spin ice. Due to the NV center’s...
Frustration denotes that not all interactions can simultaneously be satisfied. In many frustrated magnetic systems, dipolar interactions are of great importance. The dipolar interaction is often intrinsically frustrated due to its inherent anisotropy. Because of this anisotropy, an arrangement of in-plane dipoles on a square lattice is known to exhibit an order-by-disorder transition to a low...
