Electrical conductivity of (Ni,Mn,Fe,Cu)3O4 ceramic semiconductors designed for temperature and magnetic field sensing

This research is focused on designing new ceramic oxides with the spinel structure for a potential application as sensitive temperature and magnetic field sensors. In this respect, the mixtures of ferrimagnetic NiFe2O4 with low-resistive Ni0.66Cu0.41Mn1.93O4 semiconductor (molar coefficient alpha = 1/5 and 1/2) were prepared using the chemical co-precipitation technique followed by a low-temperature sintering of the cold-pressed powders. For the prepared materials, a variation of the electrical conductivity sigma dc with temperature T (in the range 50 K-400 K) is quantitatively analyzed using different theoretical concepts of the charge carrier hopping transport occurring in disordered materials with strong electron-phonon interaction. It has been shown that an increase in alpha from 0 to 1/2 causes a step-like change of the dc electrical conductivity and, simultaneously, a gradual change in the magnetization M determined in the saturation state. The temperature coefficient of resistance TCR of the prepared ceramics takes the values from -0.6%/K (at 400 K) to-19.6%/K (below 100 K). The highest absolute value of the magneto-resistance coefficient MR determined at 150 K (and at magnetic field 7 T) registered for ceramic oxide with alpha = 1/2 was found to be 3.4%.

Automated summary

This research focuses on designing new ceramic oxides for temperature and magnetic field sensors. The study examines the electrical conductivity and magnetization of prepared materials with different compositions and analyzes their temperature and magnetic field dependence. The findings show that the composition of the materials significantly affects their electrical conductivity and magnetization, indicating their potential as sensitive sensors.