Doping of Ga in antiferromagnetic semiconductor α-Cr2O3 and its effects on magnetic and electronic properties

Abstract

The samples of Ga-doped Cr2O3 have been prepared using chemical co-precipitation route. X-ray diffraction pattern and Raman spectra have indicated rhombohedral crystal structure with space group R3¯C. Magnetic measurements indicated diluted antiferromagnetic (AFM) spin order in Ga-doped α-Cr2O3 and ferrimagnetic ordering of spins at about 50–60K is confirmed from the analysis of the temperature dependence of dc magnetization and ac susceptibility data. Apart from magnetic dilution effect, the samples have shown superparamagnetic behavior below 50K due to frustrated surface spins of the nano-sized grains. The samples have shown non-linear electronic properties. The current-voltage (I-V) characteristics of the Ga-doped α-Cr2O3 samples are remarkably different from α-Cr2O3 sample. The bi-stable electronic states and negative differential resistance are some of the unique non-linear electronic properties that the I-V curves of Ga-doped samples have exhibited. Optical study revealed three electronic transitions in the samples associated with band gap energy at about 2.67–2.81eV, 1.91–2.11eV, 1.28–1.35eV, respectively. The results indicated multi-level electronic structure in Ga-doped α-Cr2O3 system.