Parallel Mode Differential Phase Contrast in Transmission Electron Microscopy, II: K₂CuF₄ Phase Transition

In Part I of this diptych, we outlined the theory and an analysis methodology for quantitative phase recovery from real-space distortions Fresnel images acquired in parallel mode transmission electron microscopy (TEM). that work, properties method, termed TEM-differential contrast (TEM-DPC), were highlighted through use simulated data. explore TEM-DPC technique with experimental cryo-TEM a thin lamella low temperature two-dimensional (2-D) ferromagnetic material, K$_2$CuF$_4$, to perform two tasks. First, using recorded below ordering temperature, compare method transport intensity one recovery, discuss relative advantages former has Second, by tracking induction sample as it is driven transition heating, extract estimates critical exponent order parameter. The value latter consistent 2-D XY class, raising prospect Kosterlitz--Thoules may have occurred.