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Electric-field controlled magnetism is a potential way to realize strong magneto-electric (ME) coupling for nonvolatile memory applications. The electric field induced nonvolatile modulated magnetization was obtained in NiFe2O4/SrRuO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) thin film heterostructures. The collective effect of charge and strain significantly modified the magnetization of the NiFe2O4 layer in NiFe2O4/SrRuO3/PMN-PT heterostructures. The analysis of XMCD data establishes that the cation (Fe3+/Ni2+) redistribution occurs on tetrahedral and octahedral sites in the electric field poled NiFe2O4 films, confirming the coupling between magnetism and ferroelectric properties. The films demonstrate repeatable switching of sign of ME output voltage α (α = dP/dH) in response to the applied positive and negative electric pulse, which can be used to store binary information in the nonvolatile manner. The electric-field-controlled switching of α in thin films offers an energy-efficient approach for low-power-consumption nonvolatile memory devices. [ABSTRACT FROM AUTHOR]

In this article, we provide an initial qualitative description of the basic magnetization reversal processes behind temperature and cooling field-dependent exchange bias effect at Co/CoO interface of Fe3O4/Alq3/Co/CoO/Au hybrid spin valve (SV) device structure. The exchange field at Co/CoO interface is observed to be inversely proportional to temperature, indicating enhanced magnetic field sensitivity of Co reverse domain nucleation at the high-temperature region. The exchange field, at constant temperature, is found to be insensitive to change in the cooling field, which may be due to efficient ferromagnetic coupling at the Co/CoO interface of the device. Sudden decrease of exchange field with training cycle number ($n$) has been observed at lower values of $n$ , which may be attributed to rearrangement of Co pinned layer spin configuration toward equilibrium. Interestingly, incorporation of antiferromagnetic CoO layer has not been observed to bring any change in magnetoresistance (MR) behavior of the exchange biased SV device, which shows a two-step switching pattern of MR at 100 K. [ABSTRACT FROM AUTHOR]

The structural, morphological, optical, and magnetic properties of BiFe1−xTixO3 (x = 0.025, 0.05, 0.075, and 0.1) nanorod (NR)-structured thin films synthesized by hot-wall spray pyrolysis have been investigated in detail. Such synthesis of one-dimensional BiFeO3 (BFO) NRs using a self-made system is unique and barely reported. NR size reduction is observed due to suppression of oxygen vacancies on Ti doping. The magnetic properties of the Ti-doped BFO NRs as shown by M–H and M–T curves reveal that the saturation magnetization increased with increasing dopant concentration. The origin and increase of the magnetization with doping of a nonmagnetic element (Ti) in BFO NRs are significant results that are discussed in detail. This unconventional magnetic property is important for multiferroic materials applications. [ABSTRACT FROM AUTHOR]

Here, we present the low temperature magnetic behaviour of epitaxial La0.7Ca0.3Mn0.85Al0.15O3 (LCMAO) thin film through a series of DC magnetic measurements. Overall behaviour inferred from the magnetization measurements indicate that the magnetic phases created due to Al doping induced inhomogeneous distribution of Mn3+ and Mn4+ ions and oxygen vacancies present in the system act like superspins, and the strong interaction among themselves results in the superspin glassy behaviour. Interactions among the superspins are marked by the aging and zero filed memory effects. The glassy magnetic phase in LCMAO is found to follow the hierarchical model of spin glasses. [ABSTRACT FROM AUTHOR]

In this study, we investigate magnetoelectric (ME) properties in nanocomposite films (P(VDF-TrFe))/SmFeO3 consist of ferroelectric copolymer, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFe)) and magnetic SmFeO3 nanoparticles. Comparative magnetization vs magnetic field hysteresis loops for un-poled and electric field poled (P(VDF-TrFe))/SmFeO3 nanocomposite films demonstrate strong electric filed control of magnetization. The nanocomposite films exhibit large exchange biasing (EB) effects in magnetic measurements near spin switching temperature (~ 100 K) of SmFeO3 and the EB effects were significantly modified under electric field (E) poled conditions (at E = 200 kV/cm), indicating ME coupling. Remarkably, we observe electric field poling induced self biased converse ME effect in the (P(VDF-TrFe))/SmFeO3 nanocomposite films. The maximum magnetoelectric output voltage (α) obtained is 55 mV/cm/Oe at Hbias = 1 kOe and 25 mV/cm/Oe at Hbias = 0, after electric field poling. The discovery of self biasing phenomenon with converse ME effects at room temperature in flexible (P(VDF-TrFe))/SmFeO3 nanocomposite films is highly desirable for device applications such as electrically controlled thin memory devices and ME sensors etc. [ABSTRACT FROM AUTHOR]

In the present work, we report the growth and properties of pulsed laser deposited epitaxial bilayer structures of Fe3O4/ZnO and ZnO/Fe3O4 on single crystal Al2O3 (0001) substrates. In order to check the structural compatibility of these structures we annealed these samples at different temperatures. Interface between the two layers plays an important role in determining the structural and magnetic properties. X-ray diffraction (XRD) studies revealed the (111) and (0001) oriented growth of Fe3O4 ZnO layers, respectively, in both the bilayers. Phi-scan shows the epitaxial nature of individual layer in both the bilayers. Raman spectra and XRD indicate the formation of ZnFe2O4 at the interface after annealing of ZnO/Fe3O4 bilayer. Magnetization measurements are in correlation with the structural results. The results indicate that Fe3O4/ZnO bilayer is more stable and has sharper interface than the other bilayer. [ABSTRACT FROM AUTHOR]

We report the x-ray absorption studies on O K, Fe L3,2, Ni L3,2, and Pr M5,4 edges in PrFe1-xNixO3 along with their structural, electrical transport, and magnetization characterizations. All the samples are in single phase having orthorhombic structure with space group Pnma for x≤0.4. Ni doping at Fe site brings the system in the conducting regime, resistivity decreases from GΩ cmto 260 mΩ cm at room temperature, and the magnetic ordering is stabilized. The temperature dependent resistivity follows the semiconducting behavior and fits well with Greaves’ variable range hopping model. The gap parameter is reduced from 2 to 0.118 eV. The materials are in weak ferromagnetic state and magnetization is gradually decreasing with the enhancement of Ni substitution, whereas magnetic anisotropy is reduced substantially. A new feature about 2.0 eV lower than the pre-edge of PrFeO3 in O K edge is observed with Ni substitution at Fe site due to the 3d contraction effect and is growing with the increase of Ni substitution. From 2p edges (L3,2 edges) of Fe and Ni, it is confirmed that both are in trivalent state and Ni is in mixed spin state with 3d7 (t2g5,eg2 and t2g6,eg1) configuration in ground state. The trivalent state of Pr is confirmed by x-ray absorption spectroscopy of Pr at M5,4 edges. These observations have been explained on the basis of charge carrier doping in PrFeO3 with the Ni substitution. The disorder induced localization is found to control the conductivity and magnetism in the present materials. The controlled doping of carriers in semiconducting regime and ferromagnetism propose these materials as a promising candidate for the spintronic applications. [ABSTRACT FROM AUTHOR]

The effect of swift heavy ion (SHI) irradiation (190 MeV Ag) on structural, electrical transport and magnetic properties of epitaxial magnetite (Fe3O4) thin films (thickness ∼70 nm) grown on MgO<100> oriented substrate have been investigated. The x-ray diffraction shows that at low fluence values up to 5×1011 ions/cm2, the strain in the films is relaxed, whereas, at higher fluence range 1×1012–1×1013 ions/cm2, the epitaxial relationship with the substrate is lost along with a phase transformation from magnetite to more oxidized magnetite phase (i.e., maghemite). The Verwey transition temperature measured by electrical transport is found to increase from 109 to 117 K with the low fluence SHI irradiation, which is related to the irradiation induced strain relaxation and structural modifications. At higher fluences the system did not show Verwey transition and the resistance is also increased. The similar results were obtained by magnetization studies. The observed magnetization at 1 T field is increased at low fluence suggesting the reduction of areas with frustrated exchange interactions associated with the cationic arrangement at the anti phase boundaries. At higher fluences it decreases monotonically, indicating the emergence of other phases. The observed modifications are explained on the basis of structural strain and disorder induced by swift heavy ions, which lead to modification of the interionic Coulomb potential at octahedral sublattices and bandwidth in this system. [ABSTRACT FROM AUTHOR]

We present low-temperature infrared measurements of magnetite (Fe3O4) thin films on Si (111) substrate across the Verwey transition temperature (TV). The line parameters of the most intense t1u mode observed in the Fourier transform infra red spectrum of the film is studied as a function of temperature. We observe that mode frequency increases abruptly at 130 K, and full width at half maxima of the mode increases abruptly at 113 K. The observations point out that structural transition may start earlier at 130 K than the actual Verwey transition (121 K) and that complete at 113 K. These results are consistent with the higher transition temperature as observed in resistivity and magnetization measurements. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of SrRuO3 having thicknesses 100, 50, 25, and 12 nm have been grown on SrTiO3 (001) substrate by pulsed laser deposition technique. The thickness dependent resistivity analysis reveals the non-Fermi-liquid type behavior by obeying T1.5 temperature dependence below the transition temperature. Increase in disorder and correlation with decrease in the film thickness lead to the transition from metallic to insulating phase for 12 nm film. Magnetic studies suggest the destruction of ferromagnetism for this film. Magnetization obeys 3D mean field model for 100 nm film and 2D Ising model for 50 and 25 nm films. [ABSTRACT FROM AUTHOR]

Utilisation of multiferroic BiFeO3 nanoparticles requires that these be embedded in a suitable matrix. We prepared BiFeO3/poly (methyl methacrylate) nanocomposite films with varying volume fraction of nanoparticles and investigated their magnetic and dielectric properties. The results obtained show that BiFeO3 nanoparticles exhibit superparamagnetic behaviour in nanocomposite films. The magnetization was observed to saturate beyond ∼13 kOe for 2.5% and 5% BFO composite films. The AC conductivity of composite films (∼10-12 Ohm-1cm-1) is also significantly reduced (by four order of magnitude) compared to that of the bulk BFO. The superparamagnetic behavior, reduced conductivity, and flexibility make these composite films attractive candidates for potential applications [ABSTRACT FROM AUTHOR]

Temperature dependent experimental magnetic Compton profiles (MCPs) of inverse spinel CoFe2-xRExO4 (x = 0.05; RE = Dy, Gd) have been decomposed into constituent profiles to determine site-specific spin moments. A comparison of MCPs of doped and undoped CoFe2O4 shows a decrease in spin moment on 5% doping of Dy and Gd. Reduction in spin moment is explained on the basis of migration of Co2+ ions from octahedral to tetrahedral sites, which is also supported by photoelectron spectroscopy measurements. The orbital moments deduced from combination of spin momentum density and magnetization data are found to be almost similar in doped ferrites. [ABSTRACT FROM AUTHOR]

Magnetic properties as a function of film thickness (2-55 nm) for magnetite (Fe[sub3]O[sub4]) thin films grown on MgO (100) substrates show that the small thickness films (⩽ 5 nm) are ferromagnetic and possess magnetization values which are much greater than that of bulk Fe[sub3]O[sub4]. The inverse thickness dependence of the magnetization points to an interface related mechanism. Whereas, our detailed spin polarized density functional theoretical calculations suggests that there is only a marginal enhancement in the local spin moments of Fe-atom in the vicinity of the Fe[sub3]O[sub4]-MgO interface and it turns out that the noncompensation of spin moments between the two magnetic sublattices of spinel Fe[sub3]O[sub4] is a major factor contributing to the enhancement of magnetization. [ABSTRACT FROM AUTHOR]

Spin and orbital magnetic moments in hole doped manganite La0.7Ca0.3Mn1-xAlxO3 (x = 0, 0.02, and 0.06) have been scrutinized using experimental spin momentum densities. An analysis of magnetic Compton profiles shows that the spin moment of Mn 3d has a major contribution towards the total spin moment and its contribution decreases as we increase the concentration of Al. The present experiment along with magnetization data predict orbital moment of -0.29 ± 0.03 μB/f.u. in the parent compound (x = 0), which almost disappears on substitution of Al. The results are explained on the basis of imbalance in Mn3+ and Mn4+ charge ratio in these compounds. [ABSTRACT FROM AUTHOR]

We have studied the structural, transport, and magnetic properties of La0.7Ca0.3-xCexMnO3 (x = 0.0, 0.025, 0.05, 0.1, and 0.15) manganite thin films on LaAlO3 (100) substrate prepared by pulsed laser deposition technique. The grown films are single phase and epitaxial in nature as revealed by x-ray diffraction and in-plane phi-scan. The temperature dependent resistivity measurements of these films reveal a metal-semiconductor transition at TP and transition temperature is found to shift lower temperature with Ce doping. Resistivity data at high temperature have been fitted with the variable range hopping model to estimate the density of states at Fermi level {N (EF)}, while at low temperature electron-electron, electron-phonon, and electron-magnon processes contribute to scattering of carriers. It was observed that N(EF) decreases with Ce doping leads to a decrease in conductivity of the Ce doped samples. We have observed maximum magnetoresistance value ∼90% near the TP. Magnetization measurements reveal that long-range ferromagnetic ordering in all samples and that saturation magnetic moment increases as x increases. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Zero-field cooled exchange bias in hexagonal YMnO3 nanoparticles" that was published in the 2013 issue.

We have studied the magnetic properties of Sr2CoO4 (SCO) thin film. Magnetic hysteresis loops of the film divulge two-phase-like magnetic behavior consisting of hard and soft magnetic phases. Temperature dependent magnetization measurements and time evolution of thermo-remanent magnetization relaxation indicate the possibility of spin-glass dynamics in SCO. The Arrott plots (M2 vs. H/M) exhibit the convex behavior, while the M4 vs. H/M plots show the linear relation near Curie temperature signifying itinerant ferromagnetism in the material, consistent with the calculated Rhodes-Wohlfarth ratio for the film. It is suggested that SCO has electrons with localized character as well as itinerant character. [ABSTRACT FROM AUTHOR]