Enhanced piezomagnetic coefficient of cobalt ferrite ceramics by Ga and Mn doping for magnetoelectric applications

Abstract

The magnetic, magnetostrictive and electrical properties of Ga-and Mn-doped cobalt ferrite, are reported as a function of composition. Materials with improved functionality for magnetoelectric composites are obtained. Magnetic characterizations reveal the effectiveness of the dopants to reduce the typically high magnetocrystalline anisotropy of cobalt ferrite and significantly enhance piezomagnetic coefficients. CoGa 0.15 F e 1.85 O 4 ceramic shows large effective piezomagnetic coefficient q 11 , 3.9×10 −6 kA −1 m, which is among the highest values reported for cobalt ferrite-based ceramics. Additionally, a two order of magnitude increase of resistivity is found after doping, which makes this material specially suitable for particulate composites. On the contrary, CoM n 0.25 F e 1.75 O 4 ceramic has the highest value of q 11 +q 21 (∼1.9×10 −6 kA −1 m), which is the relevant parameter for laminated composites. Analytical calculations of the transverse magnetoelectric coefficient α E 31 , for bilayers containing these optimized magnetostrictive phases are also reported, and they demonstrate their high potential for developing new magnetoelectric composites.

Selection and Optimization of a K0.5Na0.5NbO3-Based Material for Environmentally-Friendly Magnetoelectric Composites

“…Three-layer and multi-layer composite structures consisting of the different nine KNN-based compositions and a reference magnetostrictive oxide were simulated. Spinel CoFe 1.75 Mn 0.25 O 4 (CFM25) was chosen as a nickel-free compound with enhanced effective piezomagnetic coefficients at reduced magnetic bias field, as compared with high magnetostriction CoFe 2 O 4 [43].…”

“…In order to identify the optimum composition to be used as piezoelectric component for magnetoelectric layered composites, the material coefficients listed in Table 2 were used as input parameters to simulate, by finite element analysis, the magnetoelectric voltage responses of model composite three-layer and multi-layer structures consisting of the different LKNNT materials and spinel CoFe 1.75 Mn 0.25 O 4 (CFM25) as a reference magnetostrictive oxide. Input material coefficients for CFM25 were taken from reference [43], where longitudinal and transverse magnetostriction curves were reported, and from reference [39]. They correspond to dense, coarse grained ceramics obtained by conventional processing, and are summarized in Table 3. 2D simulations were used to scan all compositions, because they already capture all the physics and allow the optimum composition to be identified, while saving calculation time.…”

“…An example is given in the inset of Figure 10. A maximum α E 31 (max) was obtained at a given bias field, which corresponds to the maximum slope in the magnetostriction curve, and is thus characteristic of the magnetic material [43]. Ideal interfaces were assumed; i.e., strain generated in the spinel oxide under the magnetic field is fully transmitted to the perovskite layers.…”

“…In fact, L4.0Ta15 sample also has a relatively low s 11 value (see Table 2), which is advantageous for the ME response, as commented on above. 11(max) , the magnetic permeability µ 11 , the dielectric permittivity ε 11 , the electrical conductivity σ and the density ρ, in units of 10 −12 m 2 /N, 10 −6 m/kA, µ 0 (vacuum permeability), ε 0 (vacuum permittivity), 10 −4 S/m and g/cm 3 [43].…”

Lead-Free BNT–BT0.08/CoFe2O4 Core–Shell Nanostructures with Potential Multifunctional Applications

“…Indeed, in magnetoelectric composites, these curves are tightly related to the effective piezomagnetic coefficient, which can be eventually extracted from the magnetization hysteresis curves [44]. A peak value should be obtained at the position of maximum piezomagnetic coefficient, that is, the bias field for maximum response in CoFe 2 O 4 is typically above 1 kOe [46]. Note, finally, the higher longitudinal α 33 achieved with increasing the content of magnetic phase in these core-shell composites (Figure 16b).…”