Unusual doping effect of non-magnetic ion on magnetic properties of CuFe1−xGaxO2

The structural and magnetic properties of nonmagnetic Ga3+ ion doped CuFe1−xGaxO2 (x=0, 0.02, 0.03, and 0.05) single crystal samples have been investigated. In pulsed high magnetic fields, the field-induced multi-step transitions were observed in all the samples. Compared with pure CuFeO2, the transition temperatures, critical magnetic fields decrease and the magnetic hysteresis of the doped samples become small, which may result from the partial release of the spin frustration and the changes of the magnetic coupling both inter- and intra-planes due to the Ga3+ dopant. The magnetization measurements show an abnormal dilution behavior, especially in a lower temperature region, the magnetic moment was enhanced due to the nonmagnetic Ga3+ ion doping, the enhancement becomes more obviously in the sample with the Ga3+ doping level of x=0.03. These results may connected with the substitution of nonmagnetic Ga3+ ions destroying the stability of ground state and affecting the stability of the ferroelectricity incommensurate phase. Based on the experimental results, a super-cell model and their magnetic diagram were assumed.