Magnetodielectric coupling in Ferromagnetic/Ferroelectric/Ferromagnetic spin capacitor
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Magnetodielectric coupling in Ferromagnetic/Ferroelectric/Ferromagnetic spin capacitor F. Aponte1, R. Masso1, K. Dasari1, G. Sreenivasulu2, G. Srinivasan2, R. Palai 1 1 Department of Physics, University of Puerto Rico, San Juan, PR 00936, USA 2 Physics Department, Oakland University, Rochester, Michigan, USA ABSTRACT Ferromagnetic/Ferroelectric/Ferromagnetic (Ni/PZT/Ni) tri-layer artificial multiferroelectric structures in spin capacitor configuration were fabricated by sputtering ferromagnetic electrodes on PZT. Magnetocapacitance, magnetoimpedance, and phase angle measurements were carried out by a wide range of frequencies and magnetic fields at room temperature. We also compared the magnetodielectric measurements with Ni/PZT/Ag and Ag/PZT/Ag tri-layers structures. Ni/PZT/Ni spin capacitor shows a significantly different behavior compared to conventional PZT capacitor with Ag electrode and mixed electrode capacitor with one ferromagnetic and one conventional electrode. INTRODUCTION A Spin Capacitor is a device that stores both the electric charge and magnetic spin and produces both the conventional electric current and spin polarized current. The time evolution of spin polarized electrons injected into the piezoelectric material can be used for an accurate sensing of magnetoelectric field [1-4]. Multiferroic materials have attracted an increasing interest because their multi-functionality. This provides a high potential for applications in the next generation multifunctional devices. Within multiferroic materials, the coupling interaction between multiferroic orders produce some effects such as magnetoelectric or magnetodielectric effect. The magnetoelectric effect is characterized by induce of an electric polarization by magnetic field and/or induce of magnetization by the application of an electric field. This has been observed as an intrinsic effect in some single-phase materials [5-10]. There are many materials, but room temperature multiferroics are very rare. BiFeO3 is the best-known RT multiferroics, however, its high leakage current and weak magnetoelectric coupling at RT are major drawbacks for practical applications [11-13]. It is believed that combining good ferroelectric and ferromagnetic materials in composite structure could lead a strong magnetoelectric coupling [14-20]. The interactions between ferroelectric and the ferromagnetic layers produce a new coupled magnetoelectric effect, which does not present in either layer. In layered composites, the magnetoelectric effect is much higher compared to that on particulate composites made from the same materials. However, interfacial effects in laminate composites are inevitable, and this restrain the improvement and applications of magnetoelectric laminate composites due to ageing and fatigue [21-25]. Pb(ZrxTi1-x)O3 (PZT) is the most widely used piezoelectric ceramic materials. PZT has a perovskite crystal structure, each unit of which consists of a small tetravalent metal ion in a lattice of large divalent metal ions [26-35]. Many studies have been car
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