Galih Aji Prayoga, Fazri Firdaus, Zurnansyah, Harlina Ardiyanti, Nurul Imani Istiqomah, Emi Kurnia Sari, Ganesha Antarnusa, Edi Suharyadi
A fast, low-cost, and easy-to-use detection platform applicable for biosensing is increasingly needed. In this study, AAL024 giant magnetoresistance (GMR) chips were used as transducers and Fe3O4/Cs nanocomposites were used as magnetic labels. Stable structures of uniformly dispersed Fe3O4/Cs nanoparticles were obtained through a co-precipitation method with different mass ratios to achieve well-dispersed and structured Fe3O4/Cs nanoparticles. Chitosan plays a crucial role in enhancing oxidation resistance, preventing particle agglomeration and modifying the surface of Fe3O4 without changing its cubic spinel crystal structure. Structural and magnetic characterizations indicate that Fe3O4/Cs nanocomposites exhibit near-superparamagnetic behavior, spherical shape, and composition-dependent magnetic performance. Differences in crystallite size and magnetic susceptibility influence the magnetization behavior at low magnetic fields. With a bias magnetic field ( HB ) of 3.96 Oe, Fe3O4/Cs magnetic labels provide effective magnetic stray fields for sensor sensitivity measurement. Higher concentrations of magnetic labels have larger magnetic stray fields on the sensor surface, which corresponds to more nanoparticles present on the sensor surface. Among the tested nanocomposites, Fe3O4/Cs (4:1) exhibited the highest sensitivity, reaching 4.47 ± 0.2 mV/(mg/mL), with a limit of detection of 1.4 mg/mL and an R² value of 0.99. Sensitivity decreased systematically with increasing chitosan content, in agreement with the reduced low-field magnetic response. Overall, these findings demonstrate a clear relationship between composition, magnetic properties, and GMR readout performance in Fe3O4/Cs nanocomposites, and provide material-level insight for the selection of magnetic labels in low-field GMR sensing. © 2026 Elsevier B.V.
Department of Physics Education, Universitas Sultan Ageng Tirtayasa, Serang, Indonesia; Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia; Department of Physics, Institut Teknologi Sumatera, Lampung, Indonesia