Preparation of Temperature-Sensitive Magnetic Ferrite Thin-Film for Sensor Device

Temperature-sensitive magnetic bulk cores and thick films have been fabricated for thermal sensors. These magnetic substances are used in large size instruments, but cannot be adapted for miniaturization. The authors have previously been proposed a temperature-sensitive magnetic thin film annealed in oxygen atmosphere, but the saturation magnetization is below 1/5 of a bulk core. Then a temperature-sensitive Mn-Zn ferrite thin film sensor device (TMS) was prepared by sputtering and annealing in argon atmosphere. TMS's saturation magnetization is nearly equal to that of an Mn-Zn bulk ferrite. The magnetization has a marked temperature dependence like that of a bulk core or a thick film. A TMS with a small heat capacitor responds sharply to a minute temperature variation, and is therefore expected to be applicable in pyromagnetic photosensors, photo pattern sensors, and enzyme sensors.