Voltage-induced magnetic anisotropy has been quantitatively studied in polycrystalline Ni thin film deposited on flexible substrate using microstrip ferromagnetic resonance. This anisotropy is induced by a piezoelectric actuator on which the film/substrate system was glued. In our work, the control of the anisotropy through the applied elastic strains is facilitated by the compliant elastic behavior of the substrate. The in-plane strains in the film induced by the piezoelectric actuation have been measured by the digital image correlation technique. Non-linear variation of the resonance field as function of the applied voltage is found and well reproduced by taking into account the non linear and hysteretic variations of the induced in-plane strains as function of the applied voltage. Moreover, we show that initial uniaxial anisotropy attributed to compliant substrate curvature is fully compensated by the voltage induced anisotropy.

Up to now, electric field induced non-linear conduction in the Pr 1−x Ca x MnO 3 system has been ascribed to a current-induced destabilization of the charge ordered phase. However, for x ≤ 0.25, a ferromagnetic insulator state is observed and charge-ordering is absent whatever the temperature. A systematic investigation of the non-linear transport in the ferromagnetic insulator Pr 0.8 Ca 0.2 MnO 3 shows rather similar results to those obtained in charge ordered systems. However, the experimental features observed in Pr 0.8 Ca 0.2 MnO 3 are distinct in that the collapse of the CO energy gap can not be invoked as usually done in the other members of the PCMO system. We propose interpretations in which the effectiveness of the DE is restored upon application of electric field.Typeset using REVT E X 1 Hole-doped perovskite manganese oxides R 1−x AE x MnO 3 (R and AE, being trivalent rare-earth and divalent ions, respectively) are associated with a wide variety of electronic and magnetic properties depending on the value of x and the averaged A-site cation radius, r A .1 These materials have recently been the subject of intense studies due to intriguing phenomena such as charge/orbital ordering (CO) 2 or colossal magnetoresistance (CMR). 3The latter is usually interpreted by means of the double-exchange interaction (DE) scenario 4 which gives an interesting qualitative interpretation of coupled ferromagnetic ordering and metallicity. Within such a framework, the ferromagnetic (FM) ordering is related to a large electronic itinerancy i.e. metallic behavior. Among the various mixed valent manganites studied so far, the Pr 1−x Ca x MnO 3 system (PCMO) is perhaps the most interesting because it shows a great variety of ordered phases very sensitive to cation / anion doping. This produces a decrease of the magnitude of the e g bandwidth and,consequently, in a reduction in the effectiveness of the double exchange. On the other hand, for x ≤ 0.25 we deal with a very low hole concentration which does not favor a delocalized electronic state.The aim of our experience was to investigate whether a current-induced metal-insulator transition can be observed in a non-CO manganite of the PCMO system. For this purpose, a crystal of Pr 0.8 Ca 0.2 MnO 3 , not so far from the CO region, has been chosen. Although a M-I transition has not been clearly observed, the resistance for increasing bias current is drastically reduced. Moreover, strong non-linear electrical conduction is found with a NDR developing for T < T c . This behavior is not sensitive upon application of a magnetic field.Compared to already reported results, the experimental features observed here are distinct in that the collapse of the CO energy gap can not be invoke as usually done in the other members of the PCMO system. 17,18,[20][21][22][23][24][25] Using the floating-zone method with a feeding rod of nominal composition Pr 0.8 Ca 0.2 MnO 3 , a several-cm-long single crystal was grown in a mirror furnace. Two samples were cut out of the central part of this ...

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The complex impedance of a Pr 0.67 Ca 0.33 MnO 3 crystal has been measured. The frequency dependence is studied for a wide range of temperatures (50K-403K) and is found to be characteristic of relaxation process with a single Debye time relaxation constant, which is interpreted as a dielectric constant of the material. A strong peak is observed in this dielectric constant (up to 10 6 ) at the charge ordering transition suggesting an interpretation in terms of ordering of electric dipoles at T CO or in term of phase separation. Comparison with Pr 0.63 Ca 0.37 MnO 3 -in which the phase separation is much smaller and the peak in the dielectric constant is absent -suggests an interpretation in term of phase separation between insulating and metallic states.