Modulation of the properties of thin ferromagnetic films with an externally applied electric field in ferromagnetic/piezoelectric/ferromagnetic hybrids AbstractIn many cases, technological advances are based on artificial low-dimensional structures of heterogeneous constituents, thus called hybrids, that when come together they provide stand-alone entities that exhibit entirely different properties. Such hybrids are nowadays intensively studied since they are attractive for both basic research and oncoming practical applications. Here, we studied hybrids constituted of piezoelectric (PE) and ferromagnetic (FM) components in the form FM/PE/FM, ultimately aiming to provide means for the controlled modulation of the properties of the FM electrodes, originating from the strain imposed to them by the PE mediator when an electric field is applied. The PE component is in single crystal form, 0.71Pb(Mg1/ 3Nb 2/3)O3-0.29PbTiO3 (PMN-PT), while the FM outer layers are Cobalt (Co) in thin film form. Detailed magnetization measurements performed under variation of the electric field applied to PMN-PT demonstrated the efficient modulation of the properties of the Co electrodes at low temperature (coercive field modulation up to 27% and saturation magnetization absolute modulation up to 4% at T = 10 K for electric field not exceeding 6 kV/cm). The modulation degree faints upon increase of the temperature, evidencing that the thermal energy eventually dominates all other relevant energy scales. Candidate mechanisms are discussed for the explanation of these experimental observations. The results presented here demonstrate that commercially available materials can result in quantitatively noticeable effects. Thus, such elemental Co/PMN-PT/Co units can be used as a solid basis for the development of devices. 2013 AIP Publishing LLC. In many cases, technological advances are based on artificial low-dimensional structures of heterogeneous constituents, thus called hybrids, that when come together they provide stand-alone entities that exhibit entirely different properties. Such hybrids are nowadays intensively studied since they are attractive for both basic research and oncoming practical applications. Here, we studied hybrids constituted of piezoelectric (PE) and ferromagnetic (FM) components in the form FM/PE/FM, ultimately aiming to provide means for the controlled modulation of the properties of the FM electrodes, originating from the strain imposed to them by the PE mediator when an electric field is applied. The PE component is in single crystal form, 0.71Pb(Mg 1/3 Nb 2/3 )O 3 -0.29PbTiO 3 (PMN-PT), while the FM outer layers are Cobalt (Co) in thin film form. Detailed magnetization measurements performed under variation of the electric field applied to PMN-PT demonstrated the efficient modulation of the properties of the Co electrodes at low temperature (coercive field modulation up to 27% and saturation magnetization absolute modulation up to 4% at T ¼ 10 K for electric field not exceeding 6 kV/cm). The modulation degree fa...

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The ferroelectric compound family Pb(Zr x Ti1−x )O3 (PZT) is one of the most investigated and widely used piezoelectric materials. Optimization of the piezoelectric coefficients is observed for x ~ 0.52 (Pb(Zr0.52Ti0.48)O3) and is further promoted by the increase of grain size (GS). However, in some cases the piezoelectric properties of Pb(Zr0.52Ti0.48)O3 deteriorate upon processing due to the decrease of density, ρ, that is mostly ascribed to the appearance of byproduct phases. In the present study we discuss the influence of the processing conditions on the piezoelectric properties for polycrystalline Pb(Zr0.52Ti0.48)O3, specifically focusing on the sintering temperature, 1100 °C  ⩽  T sin  ⩽  1250 °C. To this end, we use atomic force microscopy (AFM), Archimedes’ method, x-ray diffraction (XRD) and a newly introduced local technique, based on a conventional optical microscope, which is further developed here to accommodate non-clamped specimens. The data obtained via this technique in the regime of relatively high electric fields evidence that the absolute piezoelectric coefficients, |d zi | (i  =  x, y) show a non-monotonic behavior with an unexpectedly high maximum value |d zi | ~ 1100 pm V−1 at T sin  =  1180 °C. These features are accompanied by a progressive increase of coercivity, reaching maximum value E C,i ~ 4.5–5.0 kV cm−1 (i  =  x, y) at T sin  =  1250 °C. To explain these findings, the |d zi | coefficients are compared with the microstructure and compositional information, coming from AFM, Archimedes’ method and XRD data. We conclude that the significantly high |d zi | values observed for samples prepared at T sin  =  1180 °C are motivated by the increase of mean GS, <GS>, while for T sin  >  1180 °C the decrease of density, ρ, ascribed to the appearance of byproduct phases, dominates and deteriorates |d zi |. These experimental results on |d zi |(T sin) are reliably reproduced by a phenomenological model with reasonable assumptions for  <GS>  (T sin) and ρ(T sin). The unexpectedly high piezoelectric coefficients, |d zi | ~ 1100 pm V−1, reported here for the first time, are provocative and call for utilization of the introduced approach in the investigation of the respective properties of other compounds.

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Low-dimensional hybrid structures of heterogeneous constituents usually exhibit abnormal properties, a fact that makes such hybrids attractive for various cryogenic and room-temperature applications. Here, we studied Co/(1 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3/Co (Co/PMN-xPT/Co) with x = 0.29 and 0.30, specifically focusing on the evolution of the remanent ferromagnetic state, mrem of the Co outer layers in the whole temperature range from 300 K down to 10 K, upon application of an external electric field, Eex. We observed that mrem was vulnerable to degradation through the occurrence of electric field-induced magnetic instabilities (EMIs) that appeared only when Eex ≠ 0 kV/cm and were facilitated as Eex increases. However, EMIs completely ceased below a characteristic temperature Tces = 170 K even for the maximum |Eex| = 5 kV/cm applied in this work. A direct comparison of the magnetization data of the Co/PMN-xPT/Co hybrids reported here with the electromechanical properties of the parent PMN-xPT crystals plausibly indicates that EMIs are motivated by the coupling of the ferromagnetic domains of the Co outer layers with the ferroelectric domains of the PMN-xPT crystal. These results highlight the drawback of EMIs in relevant hybrids and delimit the temperature regime for the reliable operation of the Co/PMN-xPT/Co ones studied here.