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

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 R (3) over barC. Magnetic measurements indicated diluted antiferromagnetic (AFM) spin order in Ga-doped alpha-Cr2O3 and ferrimagnetic ordering of spins at about 50-60 K 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 50 K 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 alpha-Cr2O3 samples are remarkably different from alpha-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 2.67-2.81 eV, 1.91-2.11 eV, 1.28-1.35 eV, respectively. The results indicated multi-level electronic structure in Ga-doped alpha-Cr2O3 system. (C) 2017 Elsevier B.V. All rights reserved.