Structural, Magnetic, and Giant Dielectric Properties of Gd Substituted CuFeO₂ Composites

To study the effects of structural modulation by doping rare earth element on the magnetic and dielectric properties, CuFe_1-xGd_xO₂ (0 ≤ x ≤ 0.2) samples are synthesized using the solid-state reaction method. The XRD and SEM results show that a small amount of Gd³⁺ ions (x ≤ 0.07) effectively occupies the Fe³⁺ site and promotes the grain growth of the CuFeO₂ system. Judging from the magnetic property measurements, the samples (x = 0, 0.01) undergo two successive magnetic transitions. Further increase of x, the magnetic transition of the samples (x ≥ 0.07) has not been detected in the testing temperature range. The magnetization hysteresis loops show that all of the samples have weak ferromagnetic properties, and the saturation magnetization is obviously enhanced with increasing x. Most interestingly, the dielectric measurements suggests that CuFeO₂ samples exhibit a giant dielectric constant (ε_γ~10⁴), and ε_γ is obviously improved (~ 4.0 × 10⁴) using the proper Gd content. The dielectric properties are explained using the internal barrier layer capacitance model (IBLC).