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1.
Polarized neutron reflectometry (PNR) is an ideal non-destructive tool for chemical and magnetic characterization of thin
films and multilayers. We have installed a position sensitive detector-based polarized neutron reflectometer at Dhruva reactor,
Trombay. In this paper we will discuss the results obtained from this instrument for two multilayer samples. The first sample
is a (Ni-Mo alloy)/Ti multilayer sample. We have determined the chemical structure of this multilayer by unpolarized neutron
reflectometry (NR). The other sample is a Fe/Ge multilayer sample for which we obtained the chemical structure by NR and magnetic
moment per Fe atom by PNR. 相似文献
2.
Detailed morphologies of the exposed surface of a Ni film vis-à-vis a buried interface below it have been determined by diffuse (off-specular) neutron scattering (DNS) and specular neutron reflectometry (NR). The exposed surface shows distinct morphological changes with respect to the buried interface, due to corrosion. The results demonstrate the strength of DNS in obtaining morphology of hidden interfaces and exposed surfaces simultaneously. 相似文献
3.
N. K. Pleshanov L. A. Axel’rod V. N. Zabenkin V. G. Syromyatnikov V. A. Ul’yanov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(6):846-855
The most detailed and reliable information about the magnetic state (magnetization depth profiles) of layers can be obtained by neutron reflectometry with vector polarization analysis. Two schemes of realization of this technique are considered. Precession coils designed to manipulate the polarization vector of monochromatic beams are used in scheme I. This scheme was tested at the neutron reflectometer NR-4M (PNPI, Gatchina). The earliest experimental data on the polarization vector rotation are reported, giving direct evidence of the wave function phase shift of a massive particle, the neutron, under total reflection. The basic elements for scheme II are remanent supermirrors. This scheme is designed for use with a white beam and is advantageous for pulse neutron sources. The effect of stray fields produced by remanent supermirrors on the neutron polarization has been theoretically and experimentally evaluated; efficient ways of compensating the stray fields are proposed. 相似文献
4.
B. M. Law M.D. Brown L. Marchand L. B. Lurio W. A. Hamilton I. Kuzmenko T. Gog S. Satija E. Watkins J. Majewski 《The European physical journal. Special topics》2009,167(1):127-132
It has proven to be a challenging task to quantitatively resolve the
interfacial profile at diffuse interfaces, such as, the adsorption profile
near a bulk binary liquid mixture critical point. In this contribution we
examine the advantages and disadvantages of a variety of experimental
techniques for studying adsorption, including neutron reflectometry, X-ray
reflectometry and ellipsometry. Short length scale interfacial features are
best resolved using neutron/X-ray reflectometry, whereas, large length scale
interfacial features are best resolved using ellipsometry, or in special
circumstances, neutron reflectometry. The use of multiple techniques
severely limits the shape of the adsorption profile that can describe all
experimental data sets. Complex interfaces possessing surface features on
many different length scales are therefore best studied using a combination
of neutron/X-ray reflectometry and ellipsometry. 相似文献
5.
Surendra Singh Saibal Basu M. Vedpathak R.H. Kodama R. Chitra Y. Goud 《Applied Surface Science》2005,240(1-4):251-259
Metal-semiconductor multilayers are interesting, artificial structures as prospective candidates for spin injection devices. A Fe–Ge multilayer sample with very thin individual layers (few crystallographic planes) has been deposited by sputtering on Si[1 0 0] substrate. We have characterized the structure of this multilayer sample using X-ray diffraction, X-ray reflectometry and neutron reflectometry. The magnetic moment density in the ferromagnetic Fe layer has been obtained by polarized neutron reflectometry and the bulk magnetic behavior of the thin film by SQUID magnetometer measurements. We found that the film is a soft ferromagnet at room temperature with a substantially reduced magnetic moment of the Fe atoms. 相似文献
6.
A. V. Kovalev 《Physics of the Solid State》2011,53(4):717-722
The specific features of the magnetic textures of the multilayer thin film systems [CoFe/TiZr]68 and [CoFe/TiZr]195 have been studied using polarized neutron reflectometry with an external magnetic field applied in different ways. A technique
has been developed for taking into account systematic errors of the measurement setup, which has made it possible to reveal
additional components in specular neutron “spinflip” reflections, whose origin is not related to the well-known mechanism
of Zeeman splitting. The samples under investigation are characterized by large differences in hysteresis curves, remanent
magnetizations, and magnetic textures. The experimental data have been analyzed using the results obtained by the author in
the previous works. 相似文献
7.
Antimonide-based superlattices dedicated to the elaboration of opto-electronic devices have been studied by X-ray scattering techniques. In particular, specular and non-specular X-ray reflectometry experiments have been performed on two MBE-samples elaborated with different shutter sequences at the interfaces. The results have shown a limitation of the incorporation of Sb species in the subsequent InAs layer for one of the samples, as expected.Then, a study on a InGaAs-cap layer/(InGaAs/AlAsSb)N superlattice grown on a InGaAs/InP buffer layer by both specular X-ray reflectometry and High resolution X-ray diffraction is reported. In particular, the results have revealed the presence of a highly disturbed thin-layer on top of the MOVPE-made GaInAs, whose presence has been explained by In-concentration modification during the desoxidation procedure at the surface of the MOVPE-made GaInAs.Beside the results on the Sb-based heterostructures, the use of X-ray scattering metrology as a routinely working non-destructive testing method has been emphasized. 相似文献
8.
Amitesh Paul Thomas KristAnke Teichert Roland Steitz 《Physica B: Condensed Matter》2011,406(8):1598-1606
We report on the enhanced capabilities of neutron reflectometer V6 at the research reactor BER II at Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) in investigating magnetic thin films and multilayers. It is now fully equipped for simultaneous measurements of specular and off-specular scattering with polarization and polarization analysis. The magnetization configuration of a [CoO/Co/Au]×16 polycrystalline multilayer at room temperature is reported in demonstrating the efficiency of the instrument. The data is simulated within the supermatrix formalism under the distorted wave Born approximation for a quantitative analysis. 相似文献
9.
S.F. Masoudi M. Vaezzadeh M. Golafrouz G.R. Jafari 《Applied Physics A: Materials Science & Processing》2007,86(1):95-100
A method is proposed for overcoming the famous ‘phase problem’ in neutron specular reflectometry. It is shown that the complex reflection coefficient of any unknown non magnetic layer, with real scattering length density, can be determined by using a magnetic transmitted media and by measuring the polarization of the reflected beam relative to the incident beam. The method follows directly from a recent one which is limited to a one-dimensional neutron polarization. Here, the theory is generalized for a neutron polarization of arbitrary direction. We show that some combinations between the polarization of the incident and reflected beam must be used to determine the reflection coefficient. Also, it is shown that instead of full polarization or reflectivity analysis, some combinations between polarization and reflectivity can be used in the analysis process. The method is supplemented with a schematic example to test the method and its stability in the presence of experimental uncertainties and roughness of the interfaces. PACS 61.12.Ha; 28.20.-v 相似文献
10.
E. Anabitarte E. G. Bustamante M. A. G. Calderón J. M. Senties 《International Journal of Infrared and Millimeter Waves》1987,8(7):733-751
This work describes a Q-band microwave reflectometer designed to obtain electron-density profiles of the plasma in the tokamak TJ-1. We present a brief study of the conditions for applying this technique to the tokamak TJ-1 as well as the experimental results obtained with a solid state sweep oscillator that eliminates the uncertainty sometimes involved in interpreting reflectometry results. 相似文献
11.
W.C. Chen R. Erwin J.W. McIver III S. Watson C.B. Fu T.R. Gentile J.A. Borchers J.W. Lynn G.L. Jones 《Physica B: Condensed Matter》2009,404(17):2663-2666
At the NIST Center for Neutron Research (NCNR), we have applied 3He neutron spin filters (NSFs) to the instruments where 3He NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and diffuse reflectometry. We present the status of our development and application of this method, including polarized gas production by spin-exchange optical pumping, magnetostatic cavities for storage of the polarized gas on the beam line, and nuclear magnetic resonance (NMR)-based, on-line monitoring and reversal of the 3He polarization. We present the status of developing user-friendly interfaces incorporated into the instrument software to handle these 3He neutron spin filters while taking data and performing data analysis. Finally we discuss the status of development of a polarization capability on the multi-axis crystal spectrometer, which requires polarization analysis over a 220° angular range. 相似文献
12.
Presently, neutron reflectometers can be divided in two main classes:
monochromatic and time-of-flight instruments. Both types of instruments
have been optimized in the last 2 decades and allow now to
measure reflectivities below 10-6 which is sufficient for most
experiments. The next big step is to perform specular reflectivity
measurements in matters of minutes rather than hours. In order to
take this step, a significant improvement in flux must be achieved.
In the past few years, several proposals have been made to
radically change the way reflectometers are operated. Methods based
either on space-time, energy-space
or spin-space encoding have been proposed. They all have the
potential to increase the flux for specular reflectivity measurements
by one to two orders of magnitude. We discuss the advantages and
shortcomings of these different techniques. 相似文献
13.
V.S. Litvin V. A. Trunov A. P. Bulkin V. A. Ul’yanov V. A. Solovei M. R. Kolkhidashvili S. I. Kalinin R. A. Sadykov E. A. Koptelov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(6):873-878
The Gorizont time-of-flight neutron reflectometer—small-angle spectrometer has been designed, manufactured, and assembled to operate with the IN-0 6 pulsed neutron source. The instrument has a vertical neutron scattering plane enabling research on liquid surfaces and interfaces. Model calculations of neutron spectra, beam profiles, and spectrometer resolutions have been performed via the Monte Carlo method. The spectrometer operates at wavelengths from 1.5 to 9 Å and ensures measurements in the momentum-transfer range of 0.003—1.5 Å-1. 相似文献
14.
V. D. Zhaketov Yu. V. Nikitenko A. V. Petrenko A. Csik V. L. Aksenov F. Radu 《Journal of Experimental and Theoretical Physics》2017,125(3):480-494
We have proposed a real-time method of neutron reflectometry. The magnetic state of the Ta/V/FM/Nb/Si ferromagnetic–superconducting system has been analyzed. Relaxation of the inhomogeneous magnetic state with a characteristic time of several hours, which depends on the magnetic field magnitude and temperature, has been observed. The relaxation of the domain structure has changed upon a transition of the V and Nb layers to the superconducting state. It has been concluded that real-time reflectometry data for polarized neutrons are important for determining the origin of magnetism in ferromagnetic–superconducting layered structures. 相似文献
15.
16.
We report on the magnetization reversal in series of
exchange-biased multilayers
NiFe(10.0 nm)/[ Ir20Mn80(6.0 nm)/Co80Fe20(3.0 nm)] N studied by specular
reflection and off-specular scattering of polarized neutrons. All
specimens are sputtered and post-annealed at 530 K (i.e. above the
IrMn Néel temperature of 520 K) in Ar atmosphere before cooling
to room temperature in the presence of a field of 130 Oe which
induces the unidirectional anisotropy. We find HEB is
dependent upon the number of bilayers N as it gradually
increases from 0.33 kOe for N=1 to a considerably higher value
of upto ≈0.9 kOe for N=10. X-ray specular and diffuse
scattering data reveal no significant variation of the lateral
correlation length and only a weak dependence of the vertical rms
interface roughness on N. Atomic and magnetic force microscopy,
however, show a strong reduction of the grain size accompanied by
distinct changes of the ferromagnetic domain structure. The
enhancement of the exchange bias effect is presumably related to
the shrinking of the related domain size in the antiferromagnet
due to the structural evolution in the multilayers. Polarized
neutron reflectometry (PNR) measurements are done at different
applied fields sweeping both branches of the hysteresis loop. The
spin-flip (SF) cross section of both the N=10 and 3 samples
show diffusely scattered intensity appears gradually as the field
approaches HEB and is most intense where the net
magnetization vanishes. The disappearance of diffuse scattering in
saturation indicates that the off-specular intensity is related to
the reversal process. The reversal proceeds sequentially starting
with the bottom (top) CoFe layer for decreasing (increasing) field
and is related to the evolution of the grain size along the stack.
The reversal of each CoFe layer is for both field branches due to
domain wall motion. Thus as a main result, we observe a
sequential and symmetric magnetization reversal in
exchange-biased multilayers. The concomitant in-plane
magnetization fluctuations revealed by off-specular
spin-flip scattering indicate a more complex reversal mechanism
than hitherto considered. Moreover, although the grain size
decreases from N=3 to 10 by a factor of about four the reversal
mechanism remains similar. 相似文献
17.
M. Al-Jawad G. Fragneto J. Liu S. R. Chang B. Clarkson 《The European physical journal. E, Soft matter》2009,30(2):175-179
In implantology it is known that fibronectin affects cell-substrate adhesion, consequently, the structure and composition of the initially adsorbed fibronectin layer to a large extent determines the biological response to a biomaterial implanted into the body. In this study we have used neutron reflectometry and quartz-crystal microbalance with dissipation to investigate the amount of fibronectin adsorbed, the layer density, thickness and structure of films adsorbed to polished silicon oxide surfaces. We have cultured MG63 osteoblast-like cells on surfaces coated and uncoated with fibronectin and monitored the cellular response to these surfaces. The results show that at fibronectin concentrations in the range 0.01 to 0.1mg/ml a single highly hydrated layer of fibronectin approximately 40-50Å in thickness adsorbs to a polished silicon oxide surface and is likely to correspond to one diffuse monolayer of fibronectin arranged side-on. Cells cultured on this fibronectin layer have dramatically different morphology and growth to those grown on bare surfaces. Using a model silicon oxide surface has enabled us to study the substrate/protein interface, together with the impact of a fibronectin layer on the cellular response using consistent experimental conditions across a unique set of experimental techniques. 相似文献
18.
作为中国散裂中子源(CSNS)工程中多功能反射(RM)谱仪一部分的3He管探测器数据获取系统不仅要具有基本的读取和处理数据的功能,还需要协调配合谱仪的整体运行,稳定可靠地与其它异构系统进行交互。通过规划数据获取的整体框架,采取有效的方式优化关键部分,另外挑选合适的三方软件包整合到数据获取系统中,达到了该系统操作方便灵活、功能完善、运行稳定可靠并且高效率,满足谱仪实验需求的目的。包括数据获取系统在内的多功能反射谱仪顺利通过了国家验收,目前这套数据获取系统已经成功应用在多功能反射谱仪的束流实验中。 相似文献
19.
We present unpolarized and polarized neutron reflectometry data on Fe/Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer thickness of 130 Å was grown on Si substrate by RF magnetron sputtering technique. Unpolarized neutron reflectivity measurement yields nuclear scattering length density profile. The magnetic scattering length density profile has been obtained from polarized neutron reflectivity measurements. 相似文献
20.
S. V. Kozhevnikov F. Ott A. Paul L. Rosta 《The European physical journal. Special topics》2009,167(1):87-92
Off-specular neutron scattering from layered resonant
systems has been studied. As an example, tri-layer neutron waveguides have
been investigated experimentally by neutron reflectometry. In such systems,
the neutron wave function is strongly localized in the guiding layer. The
resonant states in the total reflection region lead to enhanced off-specular
scattering from the interface roughness. The relation between the resonant
states and off-specular scattering is discussed. 相似文献