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Competing magnetic anisotropies in chiral crystals with Dzyaloshinskii Moriya exchange interactions can give rise to non-trivial chiral topological magnetisation configurations with new and interesting properties. One such configuration is the magnetic soliton, where the moment continuously rotates about an axis. This magnetic system can be considered to be one dimensional and, because of this, it supports a macroscale coherent magnetisation, giving rise to a tunable chiral soliton lattice (CSL) that is of potential use in a number of applications in nanomagnetism and spintronics. In this work we characterise the transitions between the forced-ferromagnetic (F-FM) phase and the CSL one in CrNb 3 S 6 using differential phase contrast imaging in a scanning transmission electron microscope, conventional Fresnel imaging, ferro-magnetic resonance spectroscopy, and mean-field modelling. We find that the formation and movement of dislocations mediate the formation of CSL and F-FM regions and that these strongly influence the highly hysteretic static and dynamic properties of the system. Sample size and morphology can be used to tailor the properties of the system and, with the application of magnetic field, to locate and stabalise normally unstable dislocations and modify their dimensions and magnetic configurations in ways beyond that predicted to occur in uniform films. KeywordsChiral soliton lattice, CrNb 3 S 6 , dislocation, differential phase contrast, transmission electron microscopy, Lorentz microscopy, Fresnel microscopy, ferromagnetic resonance spectroscopy 1 arXiv:1903.09519v1 [cond-mat.mtrl-sci]

Synopsis: The effects of columnar defects on the critical current density (J c) and electric field (E) vs. current density (J) characteristics were investigated for a YBa 2 Cu 3 O y thin film prepared using a pulsed-laser deposition method. The YBa 2 Cu 3 O y thin film was irradiated with 200 MeV Au ions from a direction = 8.8° off the c-axis. Two peaks in the angular dependence of J c were observed at the angles of = 8.8° and = 90°. These angles correspond to the directions of the columnar defect and intrinsic pinning, respectively. The E-J characteristics at various magnetic field angles can be described by the percolation transition model. The value of pinning parameter m increases at the angles of = 8.8° and = 90°. This result indicates that the efficiency of flux pinning is enhanced because fluxoids are effectively pinned by the columnar defects and intrinsic pinning or stacking faults in these directions.

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We investigate the magnetic field dependence of the spin excitation spectra of the chiral soliton lattice (CSL) in the helimagnet CrNb 3 S 6 , by means of microwave resonance spectroscopy. The CSL is a prototype of a noncollinear spin system that forms periodically over a macroscopic length scale. Following the field initialisation of the CSL, we found three collective resonance modes over an exceptionally wide frequency range. With further reducing the magnetic field towards 0 T, the spectral weight of these collective modes was disrupted by the emergence of additional resonances whose Kittel-like field dependence was linked to coexisting field polarised magnetic domains. The collective behaviour at a macroscopic level was only recovered upon reaching the helical magnetic state at 0 T. The magnetic history of this non collinear spin system can be utilized to control microwave absorption, with potential use in magnon driven devices. Recently, magnetic systems with noncollinear spin textures have attracted immense attention due to their ability to act as magnonic conduits with programmable band structure 1-4. Naturally, good field stability and spatial coherence of the underlying noncollinear magnetic structure are essential requirements to ensure efficient propagation and manipulation of the magnonic signals. In this 65 ther decreasing the field strength towards 0 T. Here, we 66 found two types of modes which we ascribe to intrinsic 67 CSL modes and ferromagnetic, Kittel-like modes, indi-68 cating the existence of a disordered CSL phase. Interest-69 ingly, upon switching the polarization of external mag-70 netic field through 0 T, we found a clear transformation

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We report broadband microwave spectroscopy in micrometer-sized platelet devices of a monoaxial chiral magnetic crystal CrNb3S6 with a helical c axis perpendicular to the device plane. In this device configuration, we found that the resonance of a chiral spin soliton lattice is insensitive to the direction of magnetic field H. In contrast to such behavior, resonance signals were largely suppressed in the ferromagnetic phase when the direction of H is parallel to a dominant component of the driving microwave field. Thus, by interchanging between the chiral spin soliton lattice and ferromagnetic phases, the microwave resonance can be switched on and off. The present device configuration allows us to demonstrate a switching performance, together with discrete changes in the resonance frequency by changing the H strength.

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