Magnetic and Humidity-Sensing Properties of Nanostructured Cu _x Co_1−x Fe₂O₄ Synthesized via Autocombustion

The magnetic nanomaterials of Cu _x Co_1−x Fe₂O₄ (x = 0.0, 0.5, and 1.0) were synthesized via autocombustion. The crystallite sizes of these materials were calculated from their X-ray diffraction peaks and were found to be within the range of 23–43 nm. The band near 575 cm⁻¹ that was observed in the Fourier transform infrared spectrum of these samples confirmed the presence of the ferrite phase. The conductivity versus temperature graph shows thermal hysteresis and exhibits the knee points at 475, 525, and 500 °C for copper ferrite, cobalt ferrite, and copper–cobalt ferrite, respectively. The M-H loops for these materials were traced using a vibrating sample magnetometer, and they indicated a significant increase in intrinsic coercivity due to the addition of Co²⁺ ions in the copper ferrite, while the remanence and saturation magnetization decreased. The ferrite materials that were used in this study exhibited good humidity sensitivity, but copper ferrite showed higher sensitivity compared to the other two materials.