The collective behaviour in ensembles of strongly interacting single-domain magnetic nanoparticles has been a matter of considerable interest over the past decades. Artificial Spin Ice (ASI) provides an experimental framework, where the geometry and interaction strength between mesospins, can be tailored at will. Furthermore, ASIs supporting thermal fluctuations are an ideal platform to study...
The possibility to tailor geometries and lattices of nanosized magnetic elements allows one to design close to arbitrary types of magnetic metamaterials. Here we will address the magnetic properties of 2DXY mesospins, having hexagonal and square lattice arrangement. We will investigate the thermally induced order-disorder phase transitions for a range of interactions by altering the lattice...
In artificial square ice spin structures, the coupling strength between perpendicular mesospins is larger than between the collinear elements. Ideally one would like to be able to choose the asymmetry of the coupling strength, allowing the alteration of the obtained order and dynamics. In a previous study this was obtained by taking advantage of the change in interactions when shifting the...
Arrays of interacting magnetic nanostructures were introduced as a powerful approach to investigate experimentally the exotic many-body physics of frustrated spin models. Following a similar strategy based on lithographically-patterned magnetic lattices, we provide a first attempt to fabricate a lab-on-chip platform to explore the physics of vertex models. The central idea of this work is to...
Avalanches are phenomena in which there is a cascade-like transition between two states and are present in many material systems, e.g. flux penetration into superconductors. Generally, avalanches are pinned at defects however, these defects are difficult to control and thus the study of the avalanche process is rather difficult. In this work, we utilize the customization properties of...
The kagome dipolar spin ice presents a rich phase diagram with intriguing magnetic properties. In particular, the so-called spin ice II phase is characterized by a very unusual behavior: magnetic order and magnetic disorder coexist at thermodynamic equilibrium. This coexistence of order and disorder can be visualized in real space: although a magnetic configuration belonging to the spin ice II...
Arrays of closely packed mesoscopic magnets provide a rich playground for investigations of collective magnetization dynamics. Here we report on the magnetization dynamics of a square array of circular iron palladium alloy nanodiscs. The dynamical properties are explored using ferromagnetic resonance measurements and micromagnetic simulations. The obtained spectra exhibit features resulting...
Vertex-Frustrated artificial spin ice systems are two-dimensional arrays of interacting ferromagnetic elements in which the moments are arranged in certain way that not all vertices can be relaxed into their lowest energy configuration simultaneously. As a consequence, these systems have degenerate ground states that include excited vertices and degeneracy comes from the allocation of excited...
The configuration of domains in ferromagnetic materials is determined by the interplay of competing energy terms. In ordered systems with zero net magnetisation, however, it is much less understood how microscopic coupling mechanisms affect the size and morphology of domains and domain walls. In order to access all relevant magnetic degrees of freedom, we investigate the formation of domains...
Artificial Spin Ices are arrays of strongly correlated nano-scale magnetic islands. While initially envisaged as a twodimensional analogue of bulk frustrated pyrochlores [1], they are now seen as a possible avenue for designing functional materials. Recently, a new tiling pattern of artificial spin ice has gained attention for its unusual ordering processes [2]. This patterning, called the...
Artificial spin systems have facilitated the experimental exploration of classical frustrated spin models, with a particular attention given to the square ice geometry. However, due to the magnetostatic nature of inter-island couplings, most artificial realizations of square spin ice do not fulfill the energetic requirements specific to the celebrated square ice model. Several approaches have...
Artificial spin ice (ASI) systems are 2D analogues of pyrochlore spin ice, which exhibit frustrated magnetism and magnetic monopole-like defects [1]. ASI is commonly studied in honeycomb or square lattices, but other geometries which exhibit frustration are of growing interest. Previous magnetotransport studies have observed an asymmetric Hall signal and postulated this is related to the phase...
Artificial spin ice (ASI) exhibits an effect referred to as return point memory (RPM) [1, 2] where the system cycles through exactly the same microstates upon subsequence field loops. The pathway the system takes as a result of the field protocol is strongly constrained by the quenched disorder of the system and the initial microstate the system starts in. While previous studies have focused...
Quantum sensing and nanoscale magnetometry using the Nitrogen-Vacancy (NV) center in diamond has opened up a wide range of sensing possibilities. The NV center is an atomic-scale defect containing a single electron spin. A single NV center integrated into the tip of an all-diamond atomic force scanning probe enables high resolution, quantitative imaging of stray magnetic fields over a wide...
Much of the intrigue and utility of nanomagnetic systems arises from the properties of specific system-wide magnetic configurations, or microstates.
From practical applications such as data storage to microstates of fundamental interest such as ground states or metastable particle-like excitations, the ability to prepare systems in any given microstate is of crucial importance....
Since the discovery of quasicrystals, the effect of aperiodicity on fundamental physical phenomena has been pursued with great interest [1,2]. Using material-by-design approach and X-ray photoemission electron microscopy imaging, we studied magnetization reversal in aperiodic Penrose P3, P2, and Ammann quasicrystal lattices. The planar artificial quasicrystals consisted of ferromagnetic...
In recent years, artificial spin systems, consisting of elongated single-domain ferromagnetic nanomagnets placed on the nodes of two-dimensional lattices and coupled via their dipolar magnetic fields, have been used to address open questions in frustrated magnetism. However, the imaging techniques so far used, are severely constrained in time and spatial resolution. We have therefore recently...
Assemblies of interacting ferromagnetic nanostructures allow real space imaging of the exotic properties often associated with frustrated magnetism. This capability to explore the rich many-body physics of frustrated spin systems through magnetic imaging triggered a wealth of studies at the frontier between nanomagnetism, condensed matter and statistical physics.
Imaging partial or complex...
With a rapidly increasing rate of global data production, high-performance and low-power computing is an inevitable necessity. The SOCRATES project investigates Self-Organizing Computational substRATES in the form of artificial spin ice and biological neural networks. The goal is to develop an understanding of the computational properties of the substrates, making way for a radical shift in...
Artificial spin ice (ASI) is a particular class of magnetic metamaterials where geometrical arrangement of single domain nano magnets well-defined lattices leads to degeneracy of low energy states and frustration. It has recently been shown that artificial spin ices can be considered as potential candidates for reprogrammable magnonic crystals [1-3]. Therefore, we have endeavored an extensive...
Artificial Spin Ices (ASIs) are arrays of strongly correlated nano-scale magnetic islands. They function as an excellent physics playground in which to study the role of topology on critical phenomena. In this work, we investigate a variation on the canonical square ice system: namely, each island in an array is rotated about its centre through some angle. This rotation angle then defines a...
Materials with interacting magnetic degrees of freedom display a rich variety of magnetic behaviour that can lead to novel collective equilibrium and out-of-equilibrium phenomena. In equilibrium, thermodynamic phases appear with the associated phase transitions providing a characteristic signature of the underlying collective behaviour.
Here we create a thermally active artificial kagome...
