Spinel is a mineral that has magmatic, metamorphic, and extraterrestrial occurrences, with compositional sensitivity to multiple thermodynamic variables. In this study, we explore a new strategy to measure interdiffusion of Cr-Al in spinel. The experimental preparation starts by using pulsed laser deposition; thin films of MgCr₂O₄ were deposited on polished MgAl₂O₄ natural crystals with very low Cr and Fe contents. The thin-film diffusion couples were annealed at atmospheric pressure in vertical gas mixing furnace at controlled fO₂ at temperatures of 1200-1325 °C. Lamellae with dimensions 10 μm x 6 μm in size and variable thickness from 0.3 μm to 1.5 μm of the diffusion couples and reference samples were prepared with a focused ion beam using a Ga source. The process was refined and the highest resolution was achieved by investigating various lamellae thicknesses and e¯ beam configurations to identify the ideal conditions for measuring diffusion profiles. Different acceleration voltages (2 keV, 5 keV, and 10 keV) and currents (0.1 to 6.4 nA) were used to obtain BSE images and perform EDX mapping. The chemical gradients were then extracted by a cross-calibration using i) correlation of the grayscale of backscatter electron imaging with composition and ii) Energy‑dispersive X‑ray Spectroscopy using Al Kα, Cr Lα and Cr Kα series intensity maps. For the steep interfaces at reference samples, we found a transient concentration range within ~140 nm at 5keV, which was used to calibrate the effective spatial resolution produced by excitation volume of the e¯ beam. A deconvolution correction using these parameters may be used for the annealed samples to obtain true diffusion profiles and calculate diffusion coefficients from fitting the corrected profiles.