New spiral state and skyrmion lattice in 3D model of chiral magnets

Abstract

We present the phase diagram of magnetic states for films of isotropic chiral\nmagnets calculated as function of applied magnetic field and thickness of the\nfilm. We have found a novel magnetic state driven by the natural confinement of\nthe crystal, localized at the surface and stacked on top of the conical bulk\nphase. This magnetic surface state has a three-dimensional (3D) chiral\nspin-texture described by the superposition of helical and cycloidal spin\nspirals. This surface state exists for a large range of applied magnetic fields\nand for any film thickness beyond a critical one. We also identified the whole\nthickness and field range for which the skyrmion lattice becomes the ground\nstate of the system. Below a certain critical thickness the surface state and\nbulk conical phase are suppressed in favor of the skyrmion lattice. Unraveling\nof those phases and the construction of the phase diagram became possible using\nadvanced computational techniques for direct energy minimization applied to a\nbasic 3D model for chiral magnets. Presented results provide a comprehensive\ntheoretical description for those effects already observed in experiments on\nthin films of chiral magnets, predict new effects important for applications\nand open perspectives for experimental studies of such systems.\n