[en] We report on a new zero-field spin-echo spectrometer (ZETA), installed at the thermal three-axis spectrometer IN3 at ILL, Grenoble. In this technique the two long precession solenoids from neutron spin echo are replaced by two pairs of magnetic resonance coils in a zero-field region. This allows easy adaptation of tilted field geometries, necessary for measurements of phonon line widths with μeV energy resolution. First test measurements of the roton line width and energy shift as well as line width of the low-Q phonon and in the 'region beyond the roton' in superfluid ⁴He are described. The results are in agreement with the literature and show the good operation of ZETA. The implementation of ZETA at the high-flux three-axis spectrometer IN20, foreseen in the near future, will increase the count rate by typically one order of magnitude

[en] Small Angle Scattering techniques are now commonly used worldwide by scientists to characterize their samples. Collimator slit size opening is one among many parameters that the user can fine tune to fit his experiment in terms of the balance between intensity, resolution and transmitted beam size on the detector. Although every instrument in the world offer this possibility, surprisingly very few offer the possibility to change the beam stop size, located in front of the detector, to match with transmitted beam size. This article describes a device allowing changing beam stops remotely and reliably during an experiment, and its integration into an existing instrument. (author)

[en] We report on the first application of polarized neutron reflectometry (PNR) to probe the re-magnetization kinetics in thin films subjected to periodic magnetic fields. Specular PNR and off- specular scattering were recorded from a 100 nm thick MBE grown Fe film under the application of AC magnetic fields with amplitudes up to 60 Oe and frequencies in the range of 0.3 - 1.8 MHz. It was found that up to 0.4 MHz a complete magnetization reversal of the Fe film takes place during each AC field cycle. Higher frequencies cause only a partial re-magnetization and above 0.8 MHz the AC field no longer alters the sample magnetization. High frequencies suppress magnetization fluctuations on a micrometer scale which are otherwise seen via off-specular scattering.

[en] We present a system which can shape the intensity of a continuous, polychromatic polarized neutron beam into a high frequency sinusoidal signal of high contrast. It is based on a pure quantum-mechanical effect (longitudinal Stern-Gerlach). The system relies on a sequence of three RF flippers, and it works virtually loss-free. The signal occurs far downstream of the last flipper within a well defined region. As an application we discuss its use in high resolution neutron spectroscopy

[en] A new experimental method (angular encoding) based on the combination of reflectometry and neutron spin-echo methods, which makes it possible to use widely collimated neutron beams and provides an angular resolution of about 0.01°, has been proposed. It was used to study magnetic thin films. In particular, the effect of Larmor pseudoprecession of neutron polarization upon reflection from a ⁵⁷Fe film with a thickness of about 100 nm was investigated, and it was shown that this method allows one to determine the absolute magnetization direction; this cannot be done using conventional reflectometry.

[en] A new experimental method (angular encoding) based on the combination of reflectometry and neutron spin-echo methods, which makes it possible to use widely collimated neutron beams and provides an angular resolution of about 0.01^o, has been proposed. It was used to study magnetic thin films. In particular, the effect of Larmor pseudoprecession of neutron polarization upon reflection from a ⁵⁷Fe film with a thickness of about 100 nm was investigated, and it was shown that this method allows one to determine the absolute magnetization direction; this cannot be done using conventional reflectometry

No abstract available

[en] Over the last decade, the systematic application of spherical neutron polarimetry (SNP) has been successfully used to investigate scientific questions which were intractable before, e.g. study of magneto-electric crystals such as LiCoPO₄ and MnGeO₃. Until now, the only device capable of performing routine SNP measurements at finite scattering angles was CryoPAD (cryogenic polarization analysis device), presented by Tasset et al. in 1989. Recently we demonstrated that an alternative setup named MuPAD (Mu-metal polarization analysis device) based on a zero-field environment produced by highly permeable mu-metal is also feasible. Here we present this new SNP device together with some first results

[en] Polarized neutrons present Larmor pseudo-precession (LPP) when reflected from magnetic films. LPP is a result of quantum interference between the different spin components of the neutron wave reflected from the substrate and the front face of a magnetic film. This interference manifests as an effective rotation of the neutron polarization vector around the magnetization direction of the film. A new method is presented here, based on the effect of LPP, which allows the absolute direction of the magnetization vector inside a layer to be determined. This is not possible using conventional reflectometry techniques

[en] The first test of angular encoding of a neutron beam with Larmor precession was performed at the spin-echo set-up of ZETA on IN3 (ILL, Grenoble, France). The polymer multilayer sample exhibits specular and off-specular scattering previously measured with reflectometry. The Yoneda scattering was discriminated from the specular reflection employing the angular encoding. The scans of the reflected and the off-specular scattered intensities as a function of the spin-echo length reveal its sinusoidal intensity dependence and the phase relation with respect to each other. The phase shift between the off-specular scattering and specular reflected intensity produced the wanted and necessary angular resolution. An estimation of the effective resolution abilities of this method in reflectometry kinematics yields that the angular encoding including subsequent deconvolution is useful for any divergent or convergent incoming or outgoing beam in order to separate signals