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Cerium substituted yttrium iron garnet (Ce:YIG) epitaxial thin films are prepared on a gadolinium gallium garnet (GGG) substrate with pulsed laser deposition. It is observed that the films grown on a GGG(111) substrate exhibit perpendicular magnetic anisotropy (PMA) as compared to films grown on a GGG(100) substrate. The developed PMA is confirmed from a magneto-optical Kerr effect, bulk magnetization, and ferromagnetic resonance measurements. Furthermore, the magnetic bubble domains are observed in the films exhibiting PMA. The observations are explained in terms of the growth direction of Ce:YIG films and the interplay of various magnetic anisotropy terms. The observed PMA is found to be tunable with the thickness of the film, and a remarkable temperature stability of the PMA is observed in all the studied films of Ce:YIG deposited on a GGG(111) substrate. [ABSTRACT FROM AUTHOR]

The study of magneto-optical (MO) properties is reported in epitaxial cerium (Ce) substituted yttrium iron garnet thin films deposited on Gd 3 Ga 5 O 12 (GGG) substrates using pulsed laser deposition technique at (i) different O 2 partial pressure (OPP) during film deposition and (ii) with different film thickness at a given OPP. The MO activity is estimated by measuring the Kerr rotation using the longitudinal magneto-optical Kerr effect with blue (405 nm), green (532 nm), and red (632 nm) incident laser light. The Kerr rotation is observed to increase with an increase in OPP and vary differently with thickness for a given OPP as a function of incident light wavelength. The results are explained in terms of the possible charge transfer mechanism for the films prepared with OPP variation and the optical interference effects in dielectric films with thickness variation. [ABSTRACT FROM AUTHOR]

The present work reports the unconventional exchange bias (EB) phenomena in an exchange-coupled hard and soft magnetic bilayer system and the tunability of EB. The EB phenomena, i.e., shifting of the hysteresis loop of the soft (Fe) layer is observed when the hard magnetic ( L 1 0 FePt) layer is under the remanent state indicating the development of unidirectional anisotropy. The nuclear resonant scattering measurements clearly reveal the development of unidirectional anisotropy in the soft magnetic (Fe) layer, when the hard magnetic layer is under the remanent state. The magnetization reversal process is investigated by measuring two in-plane orthogonal components of magnetization, i.e., parallel ( M ∥) and perpendicular ( M ⊥ ) to the applied field using the magneto-optical Kerr effect (MOKE). When the magnetic field is applied parallel (antiparallel) to the biasing field direction, ( H SAT ) magnetization reversal is nonuniform, and on the other hand, the rotation of magnetization is observed when the magnetic field is applied away from the H SAT direction. In addition, the sign inversion of the M ⊥ component is observed when the magnetic field is applied at the same angle on either side of the H SAT direction, which clearly imply the change in handedness of the chirality of spin structure during the magnetization reversal of the soft layer. Further, it is observed that the EB decreases with the increase of soft magnetic (Fe) layer thickness, demonstrating the tunable nature of EB phenomena even in these unconventional systems. [ABSTRACT FROM AUTHOR]

The effect of oxygen partial pressure (OPP) during deposition on the structural and ferroelectric properties of epitaxial SmFeO 3 (SFO) thin films is studied in the present report. The thin films are deposited using the pulsed laser ablation method. Two (00l) oriented substrates, viz., LaAlO 3 (LAO) and niobium doped SrTiO 3 (Nb:STO), are used for the deposition of films with 35 and 170 nm thicknesses at different OPP values. The prepared films are found to be of single phase and grow in the out-of-plane configuration SFO(hh0)/LAO(00l) using x-ray 2 θ − ω and ϕ scans. The epitaxial relationship between the substrate and the film, domain twinning, is confirmed by reciprocal space map measurements. Films of higher thickness exhibit tilted twin structures, more prominently for the films prepared at lower OPP. A significant change in the leakage current is observed as a function of OPP, and the results are explained in terms of the microstructure of the films. [ABSTRACT FROM AUTHOR]

Onsite magnetic moments through cation distribution and magnetocrystalline anisotropy studies of NiFe2-xRxO4 (R?=?Y and Lu; x?=?0, 0.05, and 0.075) compounds were investigated, and the results are discussed and presented in this paper. All the compounds were prepared by solid state reaction, and the compounds formed in the cubic inverse spinel phase with the space group Fd3̄m. The cation distribution, bond lengths, u-parameter, etc. were estimated through the Rietveld refinement of XRD patterns. Increment in the lattice constant was observed upon partial substitution of Fe3+ by Y3+/Lu3+. The presence of all elements and their ionic states were confirmed from X-ray photoelectron spectroscopy studies. Analyses of Mössbauer spectra revealed that the hyperfine fields and the magnetic moments at the B-site (and hence net moment) decreased with increasing Y3+/Lu3+ occupancy and that the compounds exhibited a Néel-type, collinear ferrimagnetic structure. Magnetization measurements revealed that the magnetic moment decreased with Y3+/Lu3+ substitution. The high field regimes of the magnetization curves were modeled using the law of approach to the saturation magnetization equation, and the first order cubic anisotropy constants (K1) were calculated. The temperature variation of K1 and effects of Y3+/Lu3+ substitution are explained. [ABSTRACT FROM AUTHOR]

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In the present work polycrystalline composites consisting of soft and hard ferrimagnetic phases with compositional formula (NiFe2O4)100-x – (BaFe12O19)x (x = 0,20,40,50,60,80,100) have been synthesized by sol-gel method. Thus formed materials were calcined at 1000 °C for 2 h and sintered in a microwave furnace at 1200 °C for 30 min. These composites were characterised structurally by X-ray diffraction studies and morphological studies were done using scanning electron microscopy (SEM). Analysis of XRD data confirmed hexagonal structure with P63/mmc space group for Barium hexaferrite (BFO) and cubic structure with Fd-3 m (227) space group for Nickel ferrite (NFO). Mössbauer spectroscopy measurements were also done for the selected samples and the data is analysed to extract the hyperfine parameters of both the soft magnetic and hard magnetic phases and the results are used to corroborate the observed magnetic properties. [ABSTRACT FROM AUTHOR]

Epitaxial BiFeO3 (BFO) films were deposited using pulsed laser deposition method. The prepared films were characterized using x-ray diffraction, x-ray reflectivity, ferroelectric loop tracer, and leakage current measurements before and after oxygen plasma treatment. The leakage current of the films, a crucial parameter in device applications, is observed to be reduced by two orders of magnitude with oxygen plasma treatment at room temperature. P-E hysteresis loops were observed in oxygen plasma treated BFO films. The observed results indicate the usefulness of oxygen radio frequency plasma treatment (RF 13.56 MHz), which is an effective and low temperature processing technique, in such lossy ferroelectric thin films. [ABSTRACT FROM AUTHOR]

We demonstrate enhancement in electro-optical properties of ferroelectric liquid crystal (FLC) material on incorporation of perovskite CsPbBr3 quantum dots (QDs). The underlying mechanism for enhancement in optical contrast, optical tilt angle, photoluminescence intensity and reduced saturation voltage of an FLC mixture is a consequence of incorporation of CsPbBr3 QDs. The amount of CsPbBr3 QDs in FLC material was varied as well. The experimental findings were attributed to the modification in the local ordering and orientation of the FLC molecules influenced by the presence of the QDs. Stable and improved electro-optical properties of FLC composite, by choosing an optimised concentration of the QDs in FLC is the primary finding of the present efforts. The results presented here are useful in the manufacturing of improved LC display devices based on QDs having larger viewing angles, improved contrast and lower operating voltage. [ABSTRACT FROM AUTHOR]

The magnetic and structural properties of equiatomic FePt alloy obtained from the thermal annealing of [57Fe(19 Å)/Pt(25 Å)]×10 multilayer have been studied as a function of vacuum annealing at different temperatures. The multilayers are prepared by ion beam sputtering. X-ray reflectivity (XRR), x-ray diffraction (XRD), magneto-optical Kerr effect, and conversion electron Mössbauer spectroscopy are used to characterize the as-deposited and annealed multilayers. Using XRR it is observed that due to intermixing FePt alloy formation takes place with annealing. The XRD indicated the presence of superstructure peaks due to fct FePt phase at 350 °C and above. Mössbauer measurements indicated a clear evidence for the strong exchange coupling between the soft fcc FePt and hard fct FePt phases. The results indicate that the multilayer structure does not transform directly to the ordered fct FePt, rather first a fcc FePt phase is formed and subsequently it gets converted into the fct FePt phase as a function of annealing. [ABSTRACT FROM AUTHOR]

The epitaxial films of LaFeO3 (LFO) and LaFe0.75Zn0.25O3 (LFZO) are grown on a SrTiO3 (STO) (100) substrate using pulsed laser deposition. The as-grown films have been investigated to study the structural properties and magnon excitations using temperature dependent Raman spectroscopy. X-ray diffraction and high resolution x-ray diffraction reciprocal space mapping indicate the epitaxial growth of films on the STO (100) substrate. RSM shows the broadening of the diffraction spot in the qz direction that may be due to the tilt present in the thin films, suggesting the orthorhombic growth of the films. Raman measurements on LFO and LFZO thin films have been performed for structure identification. The absence of first order phonon modes in Raman spectra suggests that the structure of films is symmetric and is coherent with the cubic substrate. High energy Raman bands with typical characteristics of two-magnon scattering appear below Neel temperature. Splitting of magnon branches is seen for both LFO and LFZO films and has been analyzed on the basis of the magnetic structure of LFO. The hardening of the magnon modes is observed as the temperature approaches towards the Neel temperature that may be attributed to the lattice contraction and correlated with a decrease in the tilt and a corresponding increase in the Heisenberg exchange constant (J) leading to a more ordered state at Neel temperature. [ABSTRACT FROM AUTHOR]