Realisation of a frustrated 3D magnetic nanowire lattice

Magneto-optical Kerr Effect Data

A 150 mW, 650 nm laser was attenuated to a power of approximately 50 mW, expanded to a diameter
of 1 cm, and passed through a Glan-Taylor polarizer to obtain an s-polarized beam. The beam was then focused onto the sample using an achromatic doublet (f= 30 cm), to obtain a spot size of approximately 50 μm2. The reflected beam was collected using an achromatic doublet (f = 10 cm) and passedthrough a second Glan-Taylor polarizer, from which the transmitted and reflected beams were directed onto two amplified Si photodetectors, yielding the Kerr and reference signals, respectively. A variable neutral density filter was used to ensure that the reference and Kerr signals were of similar values. Subtraction of the reference from the Kerr signal compensates for any change in the laser intensity drift and also eliminates any small transverse Kerr effect from the signal.

Here, we provide MOKE data for when the laser spot was placed onto the lattice (Lattice_MOKE.dat) and the film (Film_MOKE.dat). In both cases the first column is the magnetic field in units of mT and the second column is a scaled detector voltage in Volts. 

Finite element simulations
A series of micro-magnetic simulations using finite element method discretisation were performed using the NMAG code [41]. These simulations are performed by numerical integration of the Landau-Liftshitz equation upon a finite element mesh. Typical Ni81Fe19 parameters were used with zero magnetocrystalline anisotropy. The simulations were performed at a temperature of 0 K that has previously been shown to capture the correct spin-texture seen in room temperature measurements but a systematic difference in coercivity (factor of ~5) is observed. The wire cross section is a crescent shape where the arcs subtend a 160 degree angle. The inner arc is defined from a circle with 80 nm radius corresponding to the 160 nm lateral feature size of the TPL system. Line of sight deposition results in a film thickness proportional to the scalar product of the deposition direction and the surface normal therefore, the outer arc is based on an ellipse with an 80 nm minor radius and 130 nm major radius. The length of the wires is set to 780nm, due to computational restraints and the wires are arranged as single wires, bipod and tetrapod structures.

Here we present remnant states for the bipod and tetrapod structures. These are in the vtk file format and can be viewed with free software such as Paraview.

Bipod files:
180404_l_l_bipod_00-000000. vtk : Two-out state with vortex wall
180404_l_l_bipod_01-000000. vtk : One-in / One-out state

Tetrapod files:
Here the naming convention follows as described in the supplementary Fig 7 of the paper: Here the ID is a 4-bit binary number where each bit corresponds to one of the wires in the tetrapod and a 1 indicates that the wire is magnetised towards the vertex and a 0 indicates the wire magnetisation away from the vertex. Starting from the left most bit, each bit refers to:
Lower wire along [1,1,-1]
Lower wire along [-1,-1,-1]
Upper wire along [-1,1,1]
Upper wire along [1,-1,1]

Filenames:
tetra_0001_final-000004.vtk
tetra_0100_final-000003.vtk
tetra_1001_final-000002.vtk
tetra_1100_final-000001.vtk

Research results based upon these data are published at https://doi.org/10.1038/s42005-018-0104-6