Utilizing alternate target deposition to increase the magnetoelectric effect at room temperature in a single phase M-typ
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unctional Oxides Research Letter
Utilizing alternate target deposition to increase the magnetoelectric effect at room temperature in a single phase M-type hexaferrite Hessam Izadkhah, and Saba Zare, Microwave Material Laboratory of Northeastern University, Boston, MA 02115, USA; Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA Sivasubramanian Somu, Kostas Micro and Nano Fabrication Facility, Northeastern University, Boston, MA 02115, USA Fabrizio Lombardi, Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA Carmine Vittoria, Microwave Material Laboratory of Northeastern University, Boston, MA 02115, USA; Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA Address all correspondence to Hessam Izadkhah at [email protected] (Received 19 December 2016; accepted 22 May 2017)
Abstract
The Magnetoelectric (ME) effect has been observed in single phase hexaferrite bulk and thin films of SrCo2Ti2Fe8O19. In this paper we demonstrate that the ME linear coupling depends strongly on the Co ion concentration relative to the Ti ion concentration exhibiting extremum points at a concentration consistent with above formula. The Alternating Target Laser Ablation Deposition technique was utilized to deposit ME hexaferrite films for the first time. This allows for the deposition of transition metal ions at specific sites in the basic unit cell of the hexaferrite.
Introduction In magnetoelectric (ME) materials, the application of an electric field (E) and magnetic field (H ) induces magnetization (M ) and polarization (P), respectively. This effect was discovered for the first time in single phase Cr2O3 in the 1960s[1,2]; subsequently, many other ME materials have being discovered to exhibit this effect. Initially, the ME coefficient constant (α) was found to be very low, especially at room temperature. This feature limited the application of these materials and interest in ME materials diminished. ME composite materials consisting of mechanically attached piezoelectric and magnetostrictive layers, have been proposed as an alternative ME material operating at room temperature.[3] Recently, single phase hexaferrite materials have exhibited high ME coupling at room temperature.[4] Hexaferrites are a large group of ferrites that are crystalized in a hexagonal structure. They are classified into six different groups (M, W, X, Y, Z and U-types) based on the composition and the sequence of the substructures (also referred to as building blocks); for example, in an M-type, the sequence of the blocks is given by RSR*S* (Fig. 1). R* and S* are the same as R and S, but rotated 180° along the C-axis; In a Z-type, the sequence of the blocks is given by STSRS*T*S*R* in which again T* is defined similarly to R* and S*. Recently, magnetoelectric effect at room temperature has been reported for a class of M-type hexaferrite with the composition of SrCo2Ti2Fe8O19.[5] Its structure can be compared with BaFe12O19 a well
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