Raman investigation of the charge-density-wave mixed-crystal system 1T-TaS\u3csub\u3e2-x\u3c/sub\u3eSe\u3csub\u3ex\u3c/sub\u3e

The results of Raman scattering measurements on the mixed-crystal system 1T- TaS2-xSex in the commensurate charge-density-wave state are reported. In the pure compounds, our measurements indicate that a strong LA-TA phonon interaction at the distortion wave-vector results in additional coupled charge-density-wave-lattice excitations. These excitations can be followed over the whole range of concentrations in the mixed crystals. The concentration dependences of the mode frequencies are treated using an effective oscillator model

Raman investigation of the charge-density-wave mixed-crystal system 1T-TaS\u3csub\u3e2-x\u3c/sub\u3eSe\u3csub\u3ex\u3c/sub\u3e

The results of Raman scattering measurements on the mixed-crystal system 1T- TaS2-xSex in the commensurate charge-density-wave state are reported. In the pure compounds, our measurements indicate that a strong LA-TA phonon interaction at the distortion wave-vector results in additional coupled charge-density-wave-lattice excitations. These excitations can be followed over the whole range of concentrations in the mixed crystals. The concentration dependences of the mode frequencies are treated using an effective oscillator model

Mixed-crystal lattice dynamics of Hf\u3csub\u3ex\u3c/sub\u3eTi\u3csub\u3e1-x\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e

The first-order Raman spectra of the mixed-crystal layered compound HfxTi1-xSe2 have been studied over the whole range of concentrations 0≤x≤1. Both pure compounds, TiSe2 and HfSe2, have the CdI2 structure and so have two Raman-active phonons of A1g phonon is at about 205 cm -1. As x is decreased from 1.0, a new Raman peak, of A1g symmetry, appears near 180 cm -1. As x is decreased further, this peak shifts smoothly upwards in frequency, until it finally merges (by x=0.05) with the pure TiSe2 A1g phonon. A modified random-element isodisplacement model involving only short-range forces is developed to describe the observed concentration dependences of the frequencies of these phonons. The calculated concentration dependences are in good quantitative agreement with the experimental results

Magnetic and magneto-optical properties of Mn\u3csub\u3e\u3ci\u3ex\u3c/i\u3e\u3c/sub\u3ePt\u3csub\u3e1–\u3ci\u3ex–y\u3c/i\u3e\u3c/sub\u3eZn\u3csub\u3e\u3ci\u3ey\u3c/i\u3e\u3c/sub\u3e

In this work we have prepared thin films of the ternary alloy MnxPt1–x–yZny by magnetron sputtering onto quartz substrates. We have found a wide range of compositions which are strongly ferromagnetic at room temperature. A transition from a cubic to tetragonal phase with decreasing Pt content is confirmed by x-ray diffraction. X-ray diffraction measurements also show a strong (001) reflection consistent with long range order along the c axis for the tetragonal phase. These films show large complex Kerr rotations (up to 0.7°) in the visible spectrum. This combined with their anisotropic structure suggests that they may be suitable for magneto-optic data storage applications

Long-range order and magnetic properties of Mn\u3csub\u3ex\u3c/sub\u3ePt\u3csub\u3e1 – x\u3c/sub\u3e thin films

Thin films of MnxPt1–x (x = 0.18, 0.22, 0.25, 0.30, 0.34) were prepared by magnetron sputtering onto quartz substrates. After annealing in vacuum for 1 h at 850°C, X-ray diffraction indicates that the films have the Cu3Au cubic structure (a = 3.87 Å) and are highly textured with the (111) axis along the film normal. These samples have a high degree of long-range order, as indicated by the ratio of the intensities of the superlattice (100) and fundamental (200) X-ray diffraction reflections. We report here the results of magnetic and magnetooptical measurements on these samples over a wide range of temperatures

Magnetization reversal in Co/Cr multilayer films

Magnetization reversal of Co/Cr multilayer films is studied by utilizing initial magnetization curves, minor loops, isothermal and dc demagnetization remanence curves, and temperature dependence of the loops. Electron microscope observations reveal that the films consist of columnar grains of size from 400 to 800 Å. It is suggested that the magnetization reversal is dominated by rotation of single-domain grains. Numerical calculations are performed based on the Stoner–Wohlfarth coherent rotation model for noninteracting, single-domain particles of uniaxial anisotropy. The calculated results agree qualitatively with the experimental results. To investigate the quantitative differences, magnetic interactions among the grains are measured in terms of deviations from the linear Hankel plot predicted by Wohlfarth

Raman-Active Resonance Modes, Overtones, and Anharmonicity in NaCl:Cu\u3csup\u3e+\u3c/sup\u3e

The existence of an impurity-activated Eg resonance mode in NaCl:Cu+ has been suggested by several previous experiments. Raman data presented here reveal this resonance directly and also reveal the three components of the first overtone of the 23.5-cm-1 infrared resonance mode. The frequencies of the Eg resonance and the Eg component of the overtone are shifted as a result of a strong anharmonic coupling. Their line shapes and strengths are considerably altered by an interference between the Raman amplitudes. A reasonable fit to the data has been obtained using a simple theory

Structural, magnetic and magneto-transport properties of Pt-alloyed MnBi thin films

The structural, magnetic and magneto-transport properties of highly c-axis oriented Mn55−xPtxBi45 (x=0, 1.5, 3, and 4.5) thin films have been investigated. The coercivity of the Pt-alloyed thin films increases and the saturation magnetization decreases as the Pt concentration increases. The anisotropy field Ho increases as a function of Pt concentration, too but the coercivity increases more rapidly than the anisotropy field. This indicates an enhanced domain-wall pinning, caused by increased interstitial disorder due to the occupancy of regular Mn sites by Pt. The same mechanism explains the reduced magnetization. All samples exhibit a large extraordinary Hall effect with anomalous Hall coefficient about an order of magnitude larger than the ordinary Hall coefficient

MFM studies of interlayer exchange coupling in Co/Ru/Co films: Effect of Ru layer thickness

Antiferromagnetically coupled magnetic thin films are promising candidates for the design of new magnetic storage and logic devices. The ability to control the interlayer thickness, therefore the magnetic reversal response, of exchange-coupled magnetic layers is of paramount importance in nanotechnology, especially in magnetic sensing element design and applications. In this work, magnetic force microscopy (MFM) with improved sensitivity and high spatial resolution probes was used to obtain a more detailed view of magnetization reversal behavior and domain evolution in the indirect exchange-coupled trilayer system: Co/Ru/Co. The effect of the variable Ru interlayer thickness on the exchange coupling and thus the magnetic domain structure during the ferromagnetic (FM)/antiferromagnetic (AF) coupling transition in Co/Ru/Co films is well demonstrated. The MFM images display a distinct signature of AF coupling for the films with Ru thickness of 0.4 nm. MFM has proven to be an effective tool for detecting FM/AF interlayer coupling and exploring magnetic domain structures in exchange-coupled layered thin films

Magnetization precession and domainwall structure in cobalt-ruthenium-cobalt trilayers

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width that varies from about 150–60 nm. This behavior is explained in terms of a micromagnetic local-anisotropy model