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 magneto-crystalline anisotropy of cobalt ferrite and significantly enhance piezomagnetic coefficients. CoGa0.15Fe1.85O4 ceramic shows large effective piezomagnetic coefficient q11, 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, CoMn0.25Fe1.75O4 ceramic has the highest value of q11+q21 (∼1.9 × 10−6 kA−1 m), which is the relevant parameter for laminated composites. Analytical calculations of the transverse magnetoelectric coefficient α31E for bilayers containing these optimized magnetostrictive phases are also reported, and they demonstrate their high potential for developing new magnetoelectric composites.