Real-space Observation of Magnetic Excitations and Avalanche Behavior in Artificial Quasicrystal Lattices - Brajuskovic, V.; Barrows, F.; Phatak, C.D.; Petford-Long, A.K. (Materials Data Facility, 2017)
Thin films of Permalloy were patterned into quasicrystal artificial spin ice lattices. Lorentz TEM was used to image the magnetic induction in the lattices in the as-deposited state, after a demagnetization protocol, and after thermal annealing in a sputter deposition chamber.
The stacks contain two through-focus series images acquired from artificial quasicrystal lattices. The second stack is a through-focus series of images of the same pattern as in the first stack, except it has been rotated 180 degrees about the axis of the sample holder. In order to calculate the magnetic phase shift alone, the derivative of image intensity with respect to defocus at each pixel is computed for each of the two through-focus series. The two longitudinal derivatives are then subtracted from each other and divided by two. The magnetic phase shift is then be obtained by applying the transport of intensity method of phase reconstruction to the difference of the two derivatives. See the following for more details: Volkov, V.V., Zhu,Y., and De Graef, M., "A new symmetrized solution for phase retrieval using the transport of intensity equation", Micron 33 (2002) 411-416.
Keywords: magnetron sputtering; focused ion beam milling; FIB; artificial spin ice lattice; quasicrystal; thin films; magnetic materials; Lorentz microscopy; transport of intensity equation; microscopy; TEM; LTEM; Permalloy; thermal annealing; sputter deposition