Magnetic transition and defect characteristics of multiferroic CuFe1-xGaxO2 studied by positron annihilation spectra

•A systematic investigation of the effect of Ga doping on the structural and magnetic properties of CuFeO2.•Crystal defects are determined by positron annihilation spectroscopy.•There is a good correlation between antiferromagnetic stability and lattice distortion.•Crystal defects and interlayer ions in polycrystalline samples influence the magnetic properties.