Piezomagnetism of Biased Ferrites

Abstract

New developments in the synthesis and processing of magnetostrictive materials that are highly piezomagnetic in the polarized state are briefly described and interpreted in terms of the relationship for reversible stress sensitivity derived by Bozorth and Williams. In the system MnO–CoO–Fe2O3, a coupling coefficient 0.39 has been obtained for Mn0.970Co0.068Fe1.962O4 and 0.33 for Mn0.932Co0.068Fe2O4. Solid solutions of the nickel cobalt and manganese cobalt ferrites are also piezomagnetic. These materials require atmosphere control during the firing process. When similar processing is applied to the commercially established nickel cobalt ferrites, a coupling coefficient 0.42 is obtained for Ni0.974Co0.026Fe2O4 without requiring quenching from high temperatures. It is suggested that the high piezomagnetic activity of the manganese cobalt ferrites can be understood if the appropriate strain term in the expression derived by Bozorth and Williams is better identified by the easy direction magnetostriction instead of the polycrystalline magnetostriction. This interpretation leads to the prediction that magnetite with the correct cobalt ferrite addition is highly piezomagnetic.

Magnetoelectric effect in layered ferrite/PZT composites. Study of the demagnetizing effect on the magnetoelectric behavior

“…Lastly, combining Eq. (12) and (13), the electric field is related to the AC internal magnetic field :…”

“…In conclusion, good magnetic materials for magnetoelectric applications are to be chosen among the class of high magnetomechanical coupling piezomagnetic ferrite commonly used in ultrasonic transducer applications. In the 50'S and 60s, many investigations 11,12,13 have been made in the field of underwater acoustic. It turns out that cobalt substituted nickel ferrites have high magnetomechanical coupling factor, within the order of magnitude of 0.3 (at the optimum bias).…”

“…A piezoelectric/piezomagnetic bilayer can be modeled as two mechanically coupled transducers. In the 1950s and 1960s, some investigations on cobalt-substituted nickel ferrite transducers were conducted and some materials suitable for underwater applications were obtained 11,12,13 . Although the best composition of ferrite quenched in air achieved a coupling factor as high as 0.37, 12 in the 1960s research has turn towards PZT materials which have better electromechanical coupling.…”

Heterogeneous Integration for Hybrid Acoustic Devices: Gan/Cu/Yig Magnetoelastic Hbars

“…YIG has a moderate magnetostriction of 𝜆 =2.4 ppm. Other ferrites such as Ni-Co-ferrite and Ni-Mn-Coferrite have 𝜆 in excess of 100 ppm [20] and would appear to be promising candidates for MTP resonators with much larger tuning ranges, and could be investigated along similar lines.…”