MARIA: Magnetic reflectometer with high incident angle

The neutron reflectometer MARIA with polarisation analysis, which is operated by JCNS, Forschungszentrum Jülich, was designed for the investigation of thin magnetic layered structures down to the monolayer scale and lateral structures

TREFF: Reflectometer and instrument component test beamline at MLZ

TREFF is a high resolution polarized neutron reflectometer and instrument component test beamline resulting in a highly modular instrument providing a flexible beam line for various applications

Influence of Ibuprofen on Phospholipid Membranes

Basic understanding of biological membranes is of paramount importance as these membranes comprise the very building blocks of life itself. Cells depend in their function on a range of properties of the membrane, which are important for the stability and function of the cell, information and nutrient transport, waste disposal and finally the admission of drugs into the cell and also the deflection of bacteria and viruses. We have investigated the influence of ibuprofen on the structure and dynamics of L-alpha-phosphatidylcholine (SoyPC) membranes by means of grazing incidence small-angle neutron scattering (GISANS), neutron reflectometry and grazing incidence neutron spin echo spectroscopy (GINSES). From the results of these experiments we were able to determine that ibuprofen induces a two-step structuring behavior in the SoyPC films, where the structure evolves from the purely lamellar phase for pure SoyPC over a superposition of two hexagonal phases to a purely hexago- nal phase at high concentrations. Additionally, introduction of ibuprofen stiffens the membranes. This behavior may be instrumental in explaining the toxic behavior of ibuprofen in long-term application.Comment: -Improved indexing in Fig. 4e) -changed concentrations to mol% -improved arguments, however conclusions stay unchange

SEOP polarized 3 He Neutron Spin Filters for the JCNS user program

Over the past several years the JCNS has been developing in-house applications for neutron polarization analysis (PA). These methods include PA for separation of incoherent from coherent scattering in soft matter studies (SANS), and online polarization for analysis for neutron reflectometry, SANS, GISANS and eventually spectroscopy. This paper will present an overview of the user activities at the JCNS at the MLZ and gives an overview of the polarization 3He methods and devices used. Additionally we will summarise current projects which will further support the user activities using polarised 3He spin filters

Microscopic picture of magnetic correlation with loss of uniaxial anisotropy upon swift ion beam irradiation in an interlayer coupled system

Exclusive evidence of magnetic structure modification has been revealed by depth-sensitive polarized neutron scattering measurements in an antiferromagnetically coupled specimen upon swift heavy ion irradiation. The effects are independent of any structural modifications within the system (such as intermixing or roughness) that may normally have contributed to the changes in magnetic structure as well. The modifications include (a) the loss of uniaxial anisotropy, (b) changes in the variation of the mean magnetization angle and (c) changes in the variation of the lateral and longitudinal magnetic correlation lengths. We explain the changes within the thermal spike model. The possibility of controlling local magnetization can be foreseen from these results, which can be done even without damaging the structure

Untersuchung der strukturellen Phasenübergänge und Domänenbildung in den ferroischen Modellsubstanzen RbH 2 PO 4 und RbD 2 PO 4

RDP (RbH2PO4) belongs to the well known family of hydrogen bonded ferroelectrics with the composition A(H,D)2XO4 (A=K,Rb,Cs,Tl and X=P,As). On KDP (KH2PO4), the root member of the family, Busch and Scherrer discovered in 1935 the ferroelectric behaviour. A rich number of works concerning the ferroelectric - paraelectric phase transition of KDP investigated by a great variety of methods have been published. But the principal mechanism of the phase transition is still not understood. One of the basic problems here is the so called isotope effect. Just by an exchange of the protons with deuterium atoms Tc increases from 123K (KDP) to 220K (DKDP (KD2PO4)). The present work is divided into two parts. The first part is regarded to the polymorphism of RDP and DRDP. Both are less detailed investigated then in KDP and DKDP. Therefor single crystal diffraction experiments with neutron and X-ray radiation have been undertaken. As a result two new structures have been discovered and disagreements in the polymorphism are understood. The second part concentrates on the paraelectric - ferroelectric phase transition. Here are first high resolution X-ray single diffraction experiments as a function of electrical field and temperature presented. Both parts of this work have revealed a new role of the hydrogen/deuterium atoms in the structure of all phases in RDP and DRDP. The hydrogen/ deuterium atoms were interpreted in former works as individual parts of the structure. But in contrast to this they are forming [PO4H2]-groups. The former separation into ordered and disordered (H,D)-distributions is just a consequence of the in time and space averaging investigation methods. In terms of [PO4H2]-groups the paraelectric - ferroelectric phase transition of RDP(II)/(I) is of disorder - order type. In the tetragonal HT-structure local orthorhombic short range clusters with a resulting dipol moment are formed. In approaching Tc, with decreasing temperature, these clusters are growing and the resulting polarisation increases. The clusters with anti parallel polarisation are arranged by long range dipol - dipol interactions. With a critical size the growing of the clusters is blocked and 180°-twin lamellae of the ferroelectric phase are formed. Although the phase transition has a group - subgroup relation of index two, which is regarding to Landau the sufficient condition for a order disorder type, with the abrupt formation of the twin lamellae the transition is principally discontinuously and of first order

Magnetization reversal and domain correlation for a non-collinear and out-of-plane exchange-coupled system

We have investigated the impact of out-of-plane ferromagnetic (FM) anisotropy (which can be coincident with the direction of unidirectional anisotropy), where antiferromagnetic (AF) anisotropy is along the film plane. This provides a platform for non-collinear exchange coupling in an archetypal exchange coupled system in an unconventional way. We probe the in-plane magnetization by the depth-sensitive vector magnetometry technique. The experimental findings reveal a magnetization reversal (i) that is symmetric for both the branches of the hysteresis loop, (ii) that is characterized by vertically correlated domains associated with a strong transverse component of magnetization and (iii) that remains untrained (suppression of trained state) with field cycling. This scenario has been compared with in-plane magnetization reversal for a conventional in-plane unidirectional anisotropic case in the same system that shows usual asymmetric reversal and training for vertically uncorrelated domains. We explain the above observations for the out-of-plane case in terms of inhomogeneous magnetic states due to competing perpendicular anisotropies that result in non-collinear FM–AF coupling. This study provides direct evidence for the vertical correlation of domains mediated by out-of-plane exchange couplin