Nanoparticles, bulk and thin films of NiFe 2 O 4 compounds are studied by micro-Raman spectroscopy. The effect of varying the incident laser power up to 40 mW was studied in all forms of the samples. The spectra showed a large magnitude of red shift and line broadening as a result of high incident laser power. It is shown that the inverse spinel structure remains robust, and no trace of laser-induced oxidation was observed. The low-temperature study of the bulk and nanoparticles has also been carried out for elucidating thermal effects due to the high incident laser power. The rise in temperature for maximum incident laser power of 40 mW was estimated to be ∼625 • C.

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We present our study of effect of substrate induced strain on the La 5/8-y Pr y Ca 3/8 MnO 3 (y=0.45), thin films grown on LaAlO 3 , NdGaO 3 and SrTiO 3 susbtrates that show large scale phase separation. It is observed that unstrained films grown on NdGaO 3 behave quite similar to bulk material but the strained film grown on SrTiO 3 show melting of insulating phase to metallic phase at low temperatures. However, the large scale phase separation and metastable glass-like state is observed in all the films despite difference in substrate induced strain. The measurements of resistivity as a function of temperature under cooling and heating in unequal field (CHUF) protocol elucidates the presence of glass-like metastable phase generated due to kinetic arrest of first order transformation in all the films.Like structural glasses, these magnetic glass-like phase shows evidence of devitrification of the arrested charge order-antiferromagnetic insulator (CO-AFI) phase to equilibrium ferromagnetic metallic (FMM) phase with isothermal increase of magnetic field and/or isofield warming. These measurements also clearly brought out the equilibrium ground state of this system to be FMM and metastable glass-like phase to be AFI phase. PACS number(s): 75.30. Kz, 75.47.Lx, 75.60.Nt Introduction:

Utilization of magnetoelectric effects in multiferroic materials hold great potential to fabricate nonvolatile memory devices with outstanding characteristics. In particular, organic thin memories are favorable because of their environment friendly nature, mechanical flexibility, and low fabrication cost. In this work, we have demonstrated a room temperature paradigm two level nonvolatile memory operation by exploiting the nonlinear magnetoelectric effects in flexible SmFeO 3 /P(VDF-TrFE) nanocomposite films using organic ferroelectric polymer (P(VDF-TrFE)) as a host matrix. Strong strain mediated interfacial interactions between ferromagnetic and ferroelectric phases in SmFeO 3 /P(VDF-TrFE) nanocomposite films allow electric field controlled magnetic switching. The maximum magnetoelectric coefficient (α) obtained is 45 mV cm −1 Oe 1− at H bias = 1 kOe and 16 mV cm −1 Oe 1− at H bias = 0 in electrically poled composite films (30% SmFeO 3 ). The experiments demonstrate that during seven operative cycles for 1500 s, the applied positive and negative electric fields can repeatedly switch states of α. Binary information is stored by using the states of α, rather than resistance, magnetization, and electric polarization, which is advantageous to overcome the drawback of destructive reading of polarization of ferroelectric random access memory. The magnetoelectric response and the required voltage for switching of α can be tuned by varying the magnetic phase fraction (SmFeO 3 nanoparticles) in nanocomposite films. Hence, the kind of nonvolatile memory using organic, flexible magnetoelectric SmFeO 3 /P(VDF-TrFE) nanocomposite films has excellent practical characteristics, that is, compactness, easy and fast speed reading/writing operation, and reduced power consumption.

SmFeO3/poly(vinylidene fluoride) composite films exhibit tunable magnetoelectric effects induced by strong strain interactions at the interfaces.