“…However, these measurements cannot explain the driving mechanism of the appearance of spontaneous polarization without considering symmetry analysis. Moreover, it is also important to note that the parent compounds have different crystal symmetries and magnetic anisotropies of rare earths [in HoFe 3 (BO 3 ) 4 , Ho has easy-axis, and in NdFe 3 (BO 3 ) 4 , Nd has easy-plane anisotropy] [10,30,33]. Under magnetic field, Ho 0.5 Nd 0.5 Fe 3 (BO 3 ) 4 carries properties of both parent compounds, as polarization along P a decreases (H c) as in HoFe 3 (BO 3 ) 4 and increases almost twice (H a) as compared to NdFe 3 (BO 3 ) 4 [10,17,34].…”