Growth of Li x La y Sr z MnO3 thin films by pulsed laser deposition: complex relation between thin film composition and deposition parameters

Li _x La _y Sr _z MnO₃ thin films of various compositions (x,y,z) have been grown using pulsed laser deposition. The compositions of the films have been studied as a function of deposition temperature, target-to-substrate distance and deposition pressure with respect to different cation ratios of the targets by inductively coupled plasma mass spectrometry. When growing multi-elemental oxide thin films containing lithium (with its large mass difference to other elements), lithium loss is most probably inevitable. But the desired thin film composition can be achieved by selecting specific growth conditions and different target compositions. The experiments also elucidate some of the mechanisms behind the incongruent lithium transfer from the targets to thin films.

Erratum: Self-Diffusion in Amorphous Silicon [Phys. Rev. Lett. 116, 025901 (2016)]

This corrects the article DOI: 10.1103/PhysRevLett.116.025901.

Strain-induced ferromagnetism in antiferromagnetic LuMnO3 thin films

Single phase and strained LuMnO(3) thin films are discovered to display coexisting ferromagnetic and antiferromagnetic orders. A large moment ferromagnetism (≈1μ(B)), which is absent in bulk samples, is shown to display a magnetic moment distribution that is peaked at the highly strained substrate-film interface. We further show that the strain-induced ferromagnetism and the antiferromagnetic order are coupled via an exchange field, therefore demonstrating strained rare-earth manganite thin films as promising candidate systems for new multifunctional devices.

Magnetic proximity effect in YBa2Cu3O7/La(2/3)Ca(1/3)MnO3 and YBa2Cu3O7/LaMnO(3+δ) superlattices

Using neutron reflectometry and resonant x-ray techniques we studied the magnetic proximity effect (MPE) in superlattices composed of superconducting YBa2Cu3O7 and ferromagnetic-metallic La0.67Ca0.33MnO3 or ferromagnetic-insulating LaMnO(3+δ). We find that the MPE strongly depends on the electronic state of the manganite layers, being pronounced for the ferromagnetic-metallic La0.67Ca0.33MnO3 and almost absent for ferromagnetic-insulating LaMnO(3+δ). We also detail the change of the magnetic depth profile due to the MPE and provide evidence for its intrinsic nature.

Surfactant induced symmetric and thermally stable interfaces in Cu/Co multilayers

In this work we studied Ag surfactant induced growth of Cu/Co multilayers. The Cu/Co multilayers were deposited using Ag surfactant by the ion beam sputtering technique. It was found that Ag surfactant balances the asymmetry between the surface free energies of Cu and Co. As a result, the Co-on-Cu and Cu-on-Co interfaces become sharp and symmetric and thereby improve the thermal stability of the multilayer. On the basis of obtained results, a mechanism leading to symmetric and stable interfaces in Cu/Co multilayers is discussed.

Giant superconductivity-induced modulation of the ferromagnetic magnetization in a cuprate-manganite superlattice

Artificial multilayers offer unique opportunities for combining materials with antagonistic orders such as superconductivity and ferromagnetism and thus to realize novel quantum states. In particular, oxide multilayers enable the utilization of the high superconducting transition temperature of the cuprates and the versatile magnetic properties of the colossal-magnetoresistance manganites. However, apart from exploratory work, the in-depth investigation of their unusual properties has only just begun. Here we present neutron reflectometry measurements of a [Y(0.6)Pr(0.4)Ba(2)Cu(3)O(7) (10 nm)/La(2/3)Ca(1/3)MnO(3) (10 nm)](10) superlattice, which reveal a surprisingly large superconductivity-induced modulation of the vertical ferromagnetic magnetization profile. Most surprisingly, this modulation seems to involve the density rather than the orientation of the magnetization and is highly susceptible to the strain, which is transmitted from the SrTiO(3) substrate. We outline a possible explanation of this unusual superconductivity-induced phenomenon in terms of a phase separation between ferromagnetic and non-ferromagnetic nanodomains in the La(2/3)Ca(1/3)MnO(3) layers.

Direct observation of magnon fractionalization in the quantum spin ladder

We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)2CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in the saturated phase contrast sharply with a spinon continuum at intermediate fields characteristic of the Luttinger-liquid phase. By tuning the magnetic field, we drive the fractionalization of magnons into spinons and, in this deconfined regime, observe both commensurate and incommensurate continua.

[Recurrence rates after pterygium excision with sliding conjunctival flap versus free conjunctival autograft]

BACKGROUND

After simple excision without additional surgical measures, pterygiums demonstrate high recurrence rates. According to the literature, recurrences may occur in up to 83% after simple excision compared to 5-21% after excision combined with conjunctival autografts. An alternative to the free conjunctival graft is the sliding conjunctival graft.

METHODS

The data of 50 patients operated over a period of 8 years were evaluated retrospectively. The long-term results after pterygium excision with free conjunctival graft vs sliding conjunctival flap were compared with data extracted from the literature.

RESULTS

The average follow-up was 23 months. During this period, 18.5% of 27 operated eyes with free conjunctival grafts developed a recurrence of pterygium. After excision with sliding conjunctival grafts only 6.9% of 29 operated and examined eyes developed recurrences.

CONCLUSION

In the present study pterygium excision combined with sliding conjunctival graft was a simplified surgical technique with a lower recurrence rate compared to the free conjunctival graft.

Multiple magnon modes and consequences for the Bose-Einstein condensed phase in BaCuSi2O6

The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution considerably higher than in an earlier study. We observe multiple magnon modes, indicating clearly the presence of magnetically inequivalent dimer sites. The more complex spin Hamiltonian revealed in our study leads to a distinct form of magnon Bose-Einstein condensate phase with a spatially modulated condensate amplitude.

Harmonic and anharmonic thermal vibrations in cubic ZnSe

The parameters of the interatomic one-particle potentials of cubic ZnSe were determined experimentally unsing X-ray diffraction methods. The harmonic force constants α of zinc and selenium were obtained from the temperature dependence of mean square displacements evaluated from the intergrated intensities of selected reflections between 50 K and 300 K at a wavelength of λ = 0.806 Å. Least squares analysis of the experimental data yields the room temperature mean square displacements 〈u 2 Zn〉 = 0.0129(10)Å2 and 〈u2 Se〉 = 0.0115(10)Å2 i.e. harmonic force constants α Zn = 3.21(1) · 10-19 J Å-2 and α Se = 3.60(1) · 10-19 J Å-2, respectively. The third order anharmonicity constant β was determined exploiting the energy dependence of the Bijvoet ratio between the reflections 666 and 6̅6̅6̅ near the K-absorption edge of Se. It amounts to β Zn = 1.48(15) · 10-19 J Å-3 assuming β Zn = -β Se. The coefficients of the one-particle potentials of the series Ge, GaAs and ZnSe α and β decreases with rising ionicity.

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

The current best sets of X-ray structure amplitudes for GaAs, gallium arsenide, are completed by highly precise data recorded at 0.50 < sin θ/λ < 1.35 Å−1. For the strong reflections the required accuracy of ΔF/F ≤ 1% was realized by the use of Pendellösung measurements at λ = 0.30 Å, recording the integral intensities as a function of the effective thickness from ∼500 µm thick GaAs wafers. Additionally, several weak reflections were determined from their integral intensities within the kinematic limit at wavelengths λ = 0.3, 0.56 and 0.71 Å. From these data individual Debye–Waller factors for gallium and arsenic were determined using the model of independent spherical atoms [B Ga = 0.666 (4) and B As = 0.566 (4) Å2]. The extended set of experimental structure factors now available is compared with those obtained by ab initio solid-state Hartree–Fock (HF) and density functional (DF) calculations. Therefore, the theoretical data were adapted to room temperature using the experimentally evaluated Debye–Waller factors and the model mentioned above. The valence and difference charge densities obtained from experimental and theoretical data show the expected charge accumulation between nearest neighbours slightly shifted towards the arsenic site. The disagreement remaining between the experimental and theoretical data, on the one hand, and between those of both ab initio methods, on the other hand, are of the same order of magnitude.