The effect of Mn-doped zinc ferrite nanoparticles at a low volume concentration (1 × 10⁻⁴) on structural changes in the nematic liquid crystals 6CHBT and 5CB, induced by weak magnetic fields, was investigated using surface acoustic wave (SAW) and light transmission (LT) techniques. Structural changes caused by the applied magnetic field, in both increasing and decreasing modes, as well as after pulsed changes, were examined by measuring the responses of SAW attenuation and LT using a linearly polarized laser beam. The influence of nanoparticle shape (rods, needles, and clusters) and temperature on the structural changes was investigated. A shift in the threshold field and the transition temperature was observed. In addition, the magnetic properties of the individual samples in powder form were examined using M–H curves, M–T curves, and XRD patterns. The results obtained from all measurements are compared, and the effectiveness of each technique, considering the influence of nanoparticle shape and suspension stability, was evaluated.