Schweizerische Gesellschaft Für Neutronenstreuung Société .

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Number 31July 2007Schweizerische Gesellschaft für NeutronenstreuungSociété Suisse pour la Diffusion des NeutronsSwiss Neutron Scattering Society

Editorial:Editor:Swiss Neutron Scattering SocietyBoard for the Period June 2007 – June 2010:President:Dr. P. Allenspachpeter.allenspach@psi.chBoard Members:Prof. Dr. S. Decurtinssilvio.decurtins@iac.unibe.chProf. Dr. B. Schönfeld schoenfeld@iap.phys.ethz.chSecretary:Dr. S. Janssenstefan.janssen@psi.chHonorary Members: Prof. Dr. W. Hälg, ETH ZürichProf. Dr. K.A. Müller, IBM Rüschlikon and Univ. ZürichProf. Dr. A. Furrer, ETH Zürich and Paul Scherrer InstitutAuditors:Dr. W. Fischer, Paul Scherrer InstitutDr. K. Krämer, University of BerneAddress:Sekretariat SGN/SSDNPaul Scherrer Institutbldg. WLGA/0025232 Villigen PSI, SwitzerlandBank Account:phone: 41-(0)56 - 310 4666fax: 41-(0)56 - 310 3294www:http://sgn.web.psi.chPostfinance: 50-70723-6BIC:POFICHBEIBAN:CH39 0900 0000 5007 0723 6Printing:Paul Scherrer InstitutCirculation:2000, 2 numbers per yearCopyright:SGN/SSDN and the respective authorsOn the cover:An artist’s view of the new SINQ backscattering spectrometer MARS byGeorgina McIntyre. A detailed description of the instrument and its novelfeatures can be found in this issue.

Contents2The President’s Page4Minutes of the SGN/SSDN General Assembly on 26/06/200710Polarized Neutron Reflectometry at AMOR: Status and Examples16Introducing the Inverted Time-Of-Flight Backscattering Instrument,MARS at SINQ28Jeffrey Penfold: Walter Hälg Prize Winner 200729Henrik M. Rønnow: Lewy-Bertaut Prize Winner 200730Dominik Schaniel: Max-von-Laue-Prize Winner 2007329th SINQ Users’ Meeting in Lund3490th Birthday of Walter Hälg37Announcements39Conferences 2007/2008

2The President’s Pagetime. The result of these (somewhat optimistic) replies can be seen in Fig. 1. A translationinto beam weeks (Fig. 2) shows that thesenumbers will decrease beyond 2020 due toshut-downs of ageing facilities. This can inpart be compensated by ESS; certainly morethan the pure beam weak numbers indicate,since a beam week at ESS will be more productive than one at an existing facility. Adelay in building ESS or an earlier shut-downof existing sources (at the end of their “assured” lifetime) would result in a gap in theneutron capacity (at a level of slightly morethan half of its present value).However, in the past neutron sources haveDear membersnot been shut-down at the end of their lifecycle but rather for political/financial (Risø,Presently, three governments (the Spanish,Studsvik, FRJ-2) or for technical (Brookhaven)Swedish and Hungarian) have put forwardreasons. Hence, to run sources to their ageofficial bids of typically one third of the invest-limit is not an automatism but demands ament costs in order to host the Europeanhigh degree of awareness of all influencesSpallation Source ESS. This demonstrates theable to threaten a lasting operation. The twoattractiveness of ESS but, on the other hand,major threats are that such a source is re-poses the problem of the selection of its finalgarded as needless or as dangerous. To coun-location (since there exists no given procedureter the first of these two points is the duty offor such a decision making process in Europe).the scientists by doing excellent science andAnyhow, there is momentum and a there isto “sell” the results to other scientists, toconsensus that no viable alternative to ESSpoliticians and to the public. Source designers,exists. I have asked the neutron facility man-builders and operators are responsible for theagers to send me information about theirsecond point. They have to guarantee thatsource and the corresponding possible life-the source is neither regarded as dangerous

3nor that it actually is dangerous for the pub-With the hope that all sources will reachlic or the environment. Risk management attheir design lifetime and the hope for a suc-such complex installations is not an easy taskcessful quest for the ESS the future of neutronbut has to be done thoroughly by eliminatingscattering looks bright, however both will notor reducing known risks and by providingcome true automatically but needs work andprocedures for the management of the unex-dedication.pected. The worst thing is to run into disasteropen-eyed. Peter AllenspachFig. 1: Lifetime of differentneutron sources providedby the corresponding facilitymanagers.Fig. 2: Calculation of for scenariosbased on the data from Fig. 1 andthe number of beam weeks peryear and facility. Worst case: Allsources stop at the end of their“assured” operation period.

4Minutes of the SGN/SSDN General Assembly on 26/06/2007Date / Locality:June 26, 2007, University of Lund (during ECNS 2007)Begin:16:50End:17:30Participants:16 members of the society, 1 non-member1. Welcome3. Annual Report of the ChairmanThe president of the SGN/SSDN, Peter Allens P. Allenspach reports on the activities of thepach welcomes the participants to the gen-SGN/SSDN in the year 2006:eral assembly 2007. He proposes that theorder of the agenda will be slightly changeda) The SGN continued its activities regardingsince he has to leave earlier for other obliga-the supply of a 16T self-shielding magnettions and the assembly agrees.for the instruments of the SNS in OakRidge. The contract with SNS was signed.Next steps are functional tests of the2. Minutes of the Generalmagnet at the manufacturer (Bruker,Assembly 2006Zürich) and thereafter tests with neutronsat SINQ. The return for the Swiss neutronThe minutes of the General Assembly of theSGN/SSDN from 10/05/2006 published inSwiss Neutron News 29 (June 2006) are accepted without objections.scattering community will be granted access to the instrumentation at SNS.b) The Swiss use of the ILL is very sound ona level between 3.3 and 4.2%.

5c) Latest News on the ESS project will be5. SGN/SSDN Activities 2007announced during the session on neutronsources during the ECNS conference theother day.d) The approach to establish the SGN/SSDNas a member of the Swiss academy ofa) A new initiative will be taken to establishthe SGN/SSDN as member of the SwissAcademy of Science, which could not berealized in 2006.science was postponed to the year 2007b) On April 28, 2007 a dedicated symposiumdue to other obligations of the chairmanwas organized at PSI on the occasion ofrelated to the ESS project.the 90th birthday of the SGN honorarye) A welcome reception was offered by themember Prof. Walter Hälg. Many SGNsociety during the ‘PSI Summer School onmembers attended the symposium. ACondensed Matter Research 2006’ inspecial highlight was the presentation ofZuoz.the former Swiss Bundesrat Kaspar Villiger,f) Two new issues of ‘Swiss Neutron News’who was a student of Walter Hälg.were published, numbers 29 and 30, bothc) The SGN will again sponsor the Zuoz sum-issues are on the web: http://sgn.web.psi.mer school on condensed matter researchch/sgn/snn.htmlby a welcome reception.g) Presently the society has 202 members.6. Miscellaneous4. News from ENSAP. Allenspach asks the audience about theira) ENSA has now been turned into a “Swisspriorities for the next ECNS conference 2011.club” with location in Niederweningen/ZH.The candidate cities are Venice, Prague andIt is released from paying taxes and is nowEdinburgh. J. Mesot proposes to put specialallowed to possess property e.g. for donat-emphasis on the support of young scientistsing the Walter-Hälg-prize.and students. The conference fee again shouldb) The 2007 Walter-Hälg-prize will be grant-include lunch on site to enhance discussionsed to Jeffrey Penfold from the ISIS facilityamong the participants. Venice or Pragueand the new Lewy-Bertaut-prize to Henrikwould be welcome.Rønnow/EPF Lausanne. The prizes will beOn September 21 a symposium will beawarded during a special ceremony duringorganized at PSI to celebrate the 10th anni-ECNS 2007 in Lund.versary of SINQ. Invitations will also be sentc) Regarding the new ESS initiative P. Allens pach again refers to the dedicated sessionof the ECNS conference the other day.to the SGN members.T. Gutberlet proposes that the SGN partlyfunds one or two Ph.D. students in the fieldof neutron scattering in Switzerland. Theamount of funding could be in the order ofCHF 100 –200,– per month. S. Janssen refers

6to the very limited funds available but pro-The EASY Access System will grant diffrac-poses to discuss that issue in the next boardtion beamtime to scientists, who need ameeting.rapid structural characterization of samples and data analysis. Access will be openall year long and it will not be necessary7. News from the InstitutLAUE Langevin ILLto go through the standard ILL proposalsystem.b) InstrumentationThe ILL director C. Vettier reports on recentThree new instruments are on the ILLnews from the institute:roadmap: WASP (neutron spin echo), D33a) Beam time allocation and user service(small angle scattering) and THALES (triple-Over the last years the number of request axis spectrometer). Upgrades on existinged days per proposals has decreased,instruments are on their way for IN16Bhence more proposals ask for short beam(backscattering) and LADI (Laue diffrac-time periods. The average overload factortion). The following instrument projectsof the instruments is between 1.5 and 2.0have been postponed: DRACULA andexcept for the SANS instruments, whereTOPTOF.the overload is higher.The following neutron guides will be re-The block allocation of beamtime on theplaced H112, H12, H5 and H14.SANS instruments for Biology works wellThe instruments ‘D1A, IN3, IN10, DB21,and the respective teams start to collabo-IN14’ will phase out during the nextrate.years.The ILL intends to introduce the system ofThe ILL/ESRF partnership for Soft Con-longterm proposals. One condition for thedensed Matter is on good track. As oneallocation of such proposals is the relationof the first measures a joint soft matterto technical developments at ILL such aslaboratory will be installed soon.instrument components or sample envi-c) Miscellaneousronment devices.J. L. Martinez will become new ILL FrenchFrom September 2007 on it will be pos-Associate Director and Head of the Sciencesible to apply for computing time (simula-division to replace Christian Vettier.tion of experiments) together with ordinary beam time requests. This initiative ispart of the C(omputing)-lab at ILL.

78. Report of the TreasurerS. Janssen presents the annual balance sheet 2006:SFr. 4833,35Assets SGN/SSDN on 1.1.2006:Receipts [SFr]Membership-fees (cash box)550,–Membership-fees (postal check acc.)740,–Donations (cash box)Expeness [SFr]90,–Total expenses676,50– Apéro Zuoz (2006)547,50– Expenses PC account45,60– Present Güdel83,40Credit for accrued interestTotal3,–1383,–676,50Net earnings 2006:706,50Assets SGN/SSDN on 31.12.06:5539,85Balance sheet 2006:Assets [SFr] Liabilities [SFr]Postal check account3731,35Cash box1808,50Assets on 31.12.065539,85

89. Report of the AuditorsBoth Auditors (W. Fischer, K. Krämer) haveexamined the bookkeeping and the balance2006. They accepted it without any objections. The participants therefore unanimously vote for a release of the SGN/SSDNboard.10. Budget 2007The treasurer presents the following proposal for the budget 2007:Receipts [SFr]member feesinterestsExpenditures [SFr]800,–5,–fees PC account40,–Prof Hälg 901500,–Zuoz Apero 2007Totalbalance 2007805,–– 1335,–The participants accept the budget proposal unanimously.600,–2140,–

911. E lectionsThe attending members are asked to elect thePresident:Peter Allenspach,new SGN/SSDN board and the two auditorsPaul Scherrer Institutfor the period 2007– 2010. All present boardBoard members: Silvio Decurtins,members and the previous auditors volunteerUniversity of BernBernd Schönfeld,ETH Zürichasks the audience, if any other candidate isSecretary:Stefan Janssen,proposed for one of the functions. This is notPaul Scherrer Institutagain for another term of office.S. Janssen (in absence of Peter Allenspach)Auditors:Walter Fischer,He then proposes to elect all candidatesPaul Scherrer Institutin a single vote per acclamation. The membersKarl Krämer,agree to that procedure and elect the follow-University of Bernthe case.ing members unanimously for the next threeyears:S. Janssen, SGN secretaryJuly 9, 2007

10Polarized Neutron Reflectometry at AMOR:Status and ExamplesJochen Stahn, Thomas GutberletLaboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institut,5232 Villigen PSI, SwitzerlandProbing magnetism in magnetic layersprofile along the sample normal can be re-and thin films has received increasingtrieved. Layer-resolved magnetization profilesinterest in the recent years [1]. Examplesat various states of magnetization can bedemonstrating the importance to studyobtained by PNR. Off-specular PNR allows forthese phenomena include the exchangeexploring magnetic roughness and samplescoupling between similar ferromagneticwith a periodic lateral structure [3].layers separated by paramagnetic orTo enable complete polarization analysissemiconducting spacer layers, the ex-of all SF and NSF reflectivities adequate neu-change bias effect between ferro- andtron polarizing and analyzing devices are re-antiferromagnetic layers, the exchangequired. Magnetically remanent neutron su-spring effect between hard and soft mag-permirrors using the material combinationsnetic layers, reorientation phase transi-Fe/Si and FeCo/Si have been developed astions, and the proximity effect betweenversatile devices with high neutron polariza-ferromagnetic and superconducting lay-tion for usage in PNR [4]. In particular theers.polarizing remanent supermirrors show verygood performance in monochromatic as wellA powerful and versatile experimental toolas in polychromatic mode, used in broadfor the analysis of the structural and physicalwavelength band time-of-flight reflectome-properties of magnetic layer systems is polar-ters.ized neuron reflectometry (PNR) [2]. PNR al-The time-of-flight neutron reflectometerlows to measure independently the non-spin-AMOR at SINQ/PSI [5] has been equipped withflip (NSF) reflectivities R , R and the spin-flipa set of remanent supermirrors as polarizer(SF) reflectivities R , R . From these reflec-and analyzer. In the following the currenttivities, the nuclear and magnetic potentialset-up of AMOR and the performance of the

11polarizing remanent supermirrors used will beq-range is adjusted by tilting a deflectionexplained with respect to full polarizationmirror and/or the sample. A flexible softwareanalysis of specular and off-specular signals.control of the θ – 2θ-movement around axesExamples of measurements with PNR at AMORthat are not mechanically coupled has beenare given to illustrate current instrumentimplemented, which enables an extremelyperformance.simple operation for measurements. Thestandard mode of the instrument is time-offlight, which has been opened for user op-AMOReration in October 2002. An area detector ortwo single detector tubes can be operatedThe principal setup of AMOR allows measure-alternatively with new fast detector read-outments with polarized or unpolarized neutronselectronics.in white beam time-of-flight mode (1.3 Å Most optical components are riding on anλ 13 Å). The scattering plane of the sample8 m optical bench so that the chopper-detec-is oriented vertically in order to allow measure-tor distance can be varied in order to give anments at open liquid surfaces, too. The in optimum sample illumination and resolutionclination angle and thereby the accessible(Fig.1).Fig.1: View of time-of-flight reflectometer AMOR and schematic layout of the instrument.

12Remanent supermirrorsbe done using the analyzer unit in the beampath, equipped with an identical supermirror.To polarize the incoming neutron beam atWithout the analyzer unit off-specular PNRAMOR a switchable remanent supermirror hascan be measured for spin up and spin downbeen implemented in the beam path of thepolarized neutrons. An analyzer to cover theinstrument [3]. The supermirror is a FeCoV/Ti:opening for the 2D-detector system for off-N multilayer on float glass with dimension ofspecular PNR is under development.Fig. 2: FeCoV/Ti:N supermirror in polarizing unit (left). Polarization performance of supermirror at 1.0 (right).70 x 500 mm2. This mirror is placed on a rota-Magnetic sample environmenttion and translation stage below an electromagnet to change the magnetisation directionTo study magnetic materials and magnetismof the multilayer and thus to switch betweenat AMOR the instrument can be equippedspin-up and spin-down polarized neutrons. Awith dedicated sample environment to allowview of the polarizing unit is shown in Fig. 2.for low temperatures and magnetic fields atThe unit is placed within the shielding of thethe sample position. The most convenientoptical units of the reflectometer after theset-up consists of a closed cycle refrigeratorchopper housing. The polarization perform-with various sample holders to be placedance is shown for the wavelength bandwithin a Helmholtz coil for measurements upof 2 Å λ 12 Å at an angle of 1.0 of theto 0.1 T or underneath a large electromagnet supermirror towards the incoming beam.for measurements up to 1 T (Fig. 3). The CCRThe current set-up of the polarizing unitallows for cooling samples down to 10 Kproduces an average polarization of aboutwithin applied horizontal field. The maximum90% of all accepted wavelengths.sample size is 30 x 30 mm2.Full polarization analysis of the SF as wellFor lower temperature and higher mag-as NSF channels for specular reflectivities cannetic fields a cryomagnet can be placed on

13Fig. 3: CCR with Helmholtz coil at AMOR (left). CCR with 1 T electromagnet (right).the sample stage of AMOR to allow for temperatures down to 1.5 K and horizontal fieldsup to 2 T. The maximum sample size is then15 x 15 mm2.ExamplesSince availability of polarized neutrons atthe reflectometer AMOR various kinds ofexperiments have been performed successfully [6 –9]. Among others the interlayer exchange coupling in FM/AM/FM (FM ferro-Fig. 4: PNR of selected Ti(5 nm)/FeCoV (20 nm) /magnet, AF antiferromagnet) trilayers wasNiO (t nm)/ FeCoV (20 nm)/Ti(5 nm) [t 0.9 - 100probed. FM/AF/FM trilayers exhibit intriguingnm] samples during the magnetization reversal.spin configurations in the AF depending onits thickness. Possible interlayer exchangemediated by the AF was investigated by PNR.Each sample was saturated at -5000 Oe prior tothe experiment. The experimental data are represented by the symbols (Δ R (red uptriangle), R (blue downtriangle),R (green square),R From the obtained layer resolved magnetiza-(yellow circle)) and computed reflectivities by thetion profile the authors concluded that partiallines, respectively.domain wall formation in the AF is responsiblefor the observed magnetization behavior ofvery low field strengths (HFC) was studied atthe trilayers [6].various external fields (Fig. 5). The SF intensi-The exchange bias in the AF/FM multi-ties in the specular geometry along the fieldslayer of [Co/CoO/Au]16 when the system isof the decreasing branch indicated rotationalcooled below the blocking temperature atreversal of the unpinned half of moments

14(increased SF) while the pinned half showsthe difference in scattering length densitydomain wall nucleation and propagation (lack(SLD) profiles for spin-up and spin-downof SF) during the reversal [8].neutrons. Comparison of PNR data with curvesGiant proximity effect in high-temperaturecalculated for certain models presented insuperconductors between ferromagnetic andFigs. 6 lead to the conclusion that most prob-superconducting layers was studied [9]. In theably the superconducting YBCO layers aresuperconducting state the magnetic field iscoupled through the antiferromagnetic PBCOexpelled from the superconducting volume oflayer. This was also confirmed by low-energythe sample. Thus, in addition to nuclear scat-μ-SR measurements.tering, ma

Paul Scherrer Institut bldg. WLGA/002 5232 Villigen PSI, Switzerland phone: 41-(0)56 - 310 4666 fax: 41-(0)56 - 310 3294 . for the instruments of the SNS in Oak Ridge. The contract with SNS was signed. Next steps are functional tests of the magnet at the manufacturer (Bruker, .

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