Poly(2,6-dimethyl-1,4-phenylene oxide) membrane with magnetic α-Fe2O3/TiO2 fillers was exposed to varying alternating magnetic field (AMF) duration and frequency. The AMF threshold time was 8 min as mixed-matrix membrane (MMM) exposed to 11 min experienced an abrupt increase in permeability of CO2 by 785 and CH4 by 1322. Although quantitative measurements showed relatively excellent values at 11 min, prolonged exposure time reduces selectivity, possibly due to interruption in the polymer-filler interfacial area densification process. Filler distribution measured quantitatively via optical microscope and MATLAB also revealed that MMM exposed to 3.3 kHz presents the greatest dispersion metric with the least agglomeration. MMM exposed to the frequency of 30 Hz or 330 kHz suffered from either increased agglomeration size or worse dispersion. Consequently, their gas separation performances were lower than MMM exposed to 3.3 kHz. Above a critical frequency, repulsive hydrodynamic forces overcome the attractive forces between magnetic fillers. © 2022 Wiley Periodicals LLC.