Multiferroic properties of Ba²⁺ and Gd³⁺ co-doped bismuth ferrite: magnetic, ferroelectric and impedance spectroscopic analysis

Abstract

Enhanced magnetoelectric coupling is observed in bismuth ferrite samples, co-doped with non-magnetic Ba and magnetic Gd ions replacing Bi and Fe, respectively. Distortion in Fe–O octahedra has a significant effect on the magnetic properties of the samples. Ferromagnetic signature is found to increase significantly in the co-doped samples with respect to the only-Gd-doped sample both at 80 and 300 K. The co-doped samples show enhanced electric polarization as well as the highest resistivity at room temperature, which might be due to the reduction in the leakage current and oxygen vacancy in the compositions. An interesting correlation between the antiferromagnetic Néel temperature (T N) of bismuth ferrite and the temperature-dependent dielectric constant is observed in all samples. Bi0.9Ba0.1Fe0.95Gd0.05O3 ceramic possesses maximum coupling between electric dipole and magnetic dipole with an estimated magnetodielectric effect MD ([ε r(H) − ε r (0)]/ε r (0)) ∼ 380 at an applied field of 6 kOe. Impedance spectroscopy in the frequency range 40–107 Hz and temperature within 30–300 °C suggests that grain relaxation is dominant in the samples. Electrical parameters (such as capacitance and resistance) of the grains are determined using the real and imaginary parts of impedance (Z′ and Z″) and the electrical modulus (M′ and M″) plot. The results of electrical conductivity indicate a correlated barrier hopping conduction mechanism in the samples.

Dielectric anomalies due to grain boundary conduction in chemically substituted BiFeO3

“…It was also reported that this behavior can be also caused by magnetodielectric effect which is principally due to magnetoresistive response of the multiferroic sample. 73,74 It confirms that active conducting (resistive) grain boundaries are responsible for the large magnetic-dielectric response and dielectric anomaly in the vicinity of T N .…”

Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO3

“…[34][35][36] As shown in Table I, φ increase significantly with Ba-doping which is analogous with previous investigation. 37 The change in bond angle modifies the tilting angle of FeO 6 octahedron which might suppress the spiral spin structure and hence outset net magnetization in BBFO nanoparticles. On the contrary, according to Goodenough-Kanamori rule the AFM superexchange interaction between two magnetic ions with partially filled d orbital increases with increasing bond angle, φ and is strongest when φ = 180 o .…”

Synthesis and enhancement of multiferroic properties of (x)Ba0.95Sr0.05TiO3–(1−x)BiFe0.90Dy0.10O3 ceramics

“…Also the systemic research on complex impedance and ME coupling of BST-BFO ceramics is not published yet. On the other hand, substitution of rare-earth elements in the B-site of BFO perovskite is rare but improved magnetic properties are expected by the substitution of magnetically active rare-earth atoms [11].…”

“…On the other hand, enhanced magnetic properties are noticed for the case of Fe-deficient Gd doped BFO [12]. Due to the 4 difference of magnetic moment of Fe 3+ (μ eff = 5.92 µ B ) and Gd 3+ (μ eff =7.63 µ B ) and ionic radii between the cations, there is a significant lattice distortion and hence improve magnetic properties [11]. It is expected that the magnetically active rare earth atom Dy will play the same role.…”