WEMS2016

30 Jun 2016, 13:30 → 2 Jul 2016, 21:00 Europe/Zurich

Haraldur Pall Gunnlaugsson (KU Leuven (BE)), Karl Johnston (CERN), Lino Miguel Da Costa Pereira (KU Leuven (BE))

WEMS 2016, Leuven, Belgium 30/6-2/7 2016

The workshop on applications of emission Mössbauer spectroscopy (WEMS) is organized by members of the Mössbauer collaboration at ISOLDE/CERN. The group has for many years applied implantation of short-lived radioactive parent isotopes produced at the  ISOLDE facility at CERN for emission Mössbauer spectroscopy, mostly in the field of material sciences. The next workshop is organized as a satellite meeting of the International Conference on Hyperfine Interactions and their Applications.  

The aim of the workshop is to review the main findings of the collaboration in recent year(s) and bring together groups with interest in emission Mössbauer spectroscopy for studies in material sciences and/or biophysics. 

Currently, ISOLDE is undergoing a major upgrade (the HIE-ISOLDE) aimed to provide higher intensity beams and increased flexibility, which will enable new applications of emission Mössbauer spectroscopy. 

Registration for the workshop is free but mandatory. 

Thursday 30 June

13:30 → 15:05 Introduction

Convener: Guido LANGOUCHE (Katholieke Universiteit Leuven)

13:30 Welcome and practicals

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

13:35 The ISOLDE facility

I will give a brief general overview of ISOLDE

Speaker: Torben Esmann Molholt (CERN)

13:50 Solid State Physics and Perturbed Angular Correlations at ISOLDE

Since the late 70s researchers at ISOLDE have been applying radioactive nuclear techniques to materials science and biophysics research. A considerable infrastructure has been built up on-site to allow scientists to perform experiments using short-lived isotopes [COR2012]. The production of radioactive isotopes online with big yields, elemental and isotopic purity allow the choice of the right probe radioactive element / isotope adequate to study each problem. In this context, Deep Level Transient Spectroscopy and Photoluminescence with radioactive Isotopes and nuclear techniques such as Perturbed Angular Correlations, Emission Channeling, ß-Nuclear Magnetic Resonance, Secondary Ion Mass Spectroscopy, Spreading Resistance Profiling and Mössbauer are very powerful to characterize new materials, particularly from an atomic point of view. ISOLDE is the world reference on production and delivery of radioactive beams of high purity dedicated to many different purposes for, e.g., atomic, nuclear, solid state, biophysics, and medical research. This laboratory is also a pioneer in the use of nuclear techniques – with an enriched potential due to the wide number of available radioactive probe elements – while studying the atomic scale interactions of the probe nuclei with its neighbourhood. Gamma-Gamma, Electron-Gamma and Beta-Gamma Perturbed Angular Correlation (GEBPAC) experiments appear in this concept to provide information about the hyperfine interactions between extranuclear electromagnetic fields and nuclear moments of a radioactive probe nucleus placed on a particular atomic site of the material. The precession frequency is determined from the observed modulations of PAC spectra and provides information about electric and magnetic fields generated by the electronic and ionic charge distribution in the neighborhood of the probe nuclei. This contribution explores the history of the PAC technique, isotopes and its application to new materials.
References
[ABR1953] A. Abragam and R. V. Pound. Physical Review 92, n. 4, 943 (1953).
[COR2012] J. G. Correia, K. Johnston and U. Wahl. Radiochim. Acta 100, 127 (2012).
[SCH1996] G. Schatz and A. Weidinger, Nucl. Cond. Matt. Phys., Wiley, Chichester (1996).

Speaker: Dr Juliana Schell (Experimentalphysik, Universität des Saarlandes, Germany)

Juliana_Schell_SSPtalk_WEMS2016.pdf

Juliana_Schell_SSPtalk_WEMS2016.pptx

14:20 Physics at IKS, KU Leuven

Speaker: Prof. Andre Vantomme (IKS, KU Leuven)

14:45 Emission channeling at ISOLDE

Speaker: Tiago Abel De Lemos Lima (KU Leuven (BE))

15:05 → 15:25 Coffee

15:25 → 16:45 eMS

Convener: Lino Miguel Da Costa Pereira (KU Leuven (BE))

15:25 eMS@ISOLDE, equipment and status of current experiments

I will give a overview of emission Mössbauer spectroscopy at ISOLDE, with emphasiz on on-line experiments using short lived parent isotopes

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

15:50 Dy-Gd beam for 151Eu eMS and prelinimary results

Beam production and initial results

Speaker: Torben Esmann Molholt (CERN)

16:05 High transition energy isotopes, the I161 experiment

Plans for I161 and cryostat facilities at ISOLDE

Speakers: Haraldur Pall Gunnlaugsson (KU Leuven (BE)), Torben Esmann Molholt (CERN)

16:20 Use of 181Ta eMS

Properties of 181Ta, and its use for eMS

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

Friday 1 July

09:00 → 10:35 New experiments and facilities

Convener: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

09:00 Topological insulators, Exp. IS 612

Overview of experiment

Speaker: Lino Miguel Da Costa Pereira (KU Leuven (BE))

09:20 Results obtained in topological insulators

Speaker: Hilary Masenda (University of Witwatersrand)

09:35 The CERN MEDICIS facility for the production of medical research radioisotopes — et plus si affinités?

CERN MEDical Isotopes Collected from ISolde (MEDICIS) is an offline separator under construction next to CERN ISOLDE, where targets parasitically irradiated at ISOLDE can be used to collect long-lived radioisotopes (min 1 hour half-life). The main goal of this facility is to provide a large catalog of radioisotopes to support the medical research on functional imaging and targeted radio-therapy. Other use of this facility may however be explored, especially in synergy for other research facilities at CERN (e.g Mössbauer, nToF).

Speaker: Prof. Thomas Elias Cocolios (KU Leuven - IKS)

cocolios - wems.pdf

10:15 Cold CEMS measurements at KU Leuven

An overview of a new setup for CEMS measurements down to 2.1 K is described, together with some results on calibration foils and 57Fe in STO

Speaker: Valerie Augustyns (K)

10:35 → 10:55 coffee

10:55 → 12:25 AlGaN:Mn

Convener: Tiago Abel De Lemos Lima (KU Leuven (BE))

10:55 AlGaN:Mn overview

General overview of manganese doped AlGaN

Speaker: Aitana Tarazaga (JKU, Linz, Austria)

11:10 The IS576 experiment

The IS576 experiment. Overview of the datasets obtained so far

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

11:20 Analysis of the data obtained with Mn beam and interpretation

I will give a thourough overview of the analysis, and how this is to be interpreted

Speakers: Aitana Tarzaga (JKU, Linz, Austria), Haraldur Pall Gunnlaugsson (KU Leuven (BE))

11:45 Results obtained with In beam in AlGaN's

What components and why

Speaker: Hilary Masenda (University of Witwatersrand)

12:05 AlGaN status and conclusions

Overall status of the IS576 experiment, are we done? What next?

Speakers: Aitana Tarzaga (JKU, Linz, Austria), Haraldur Pall Gunnlaugsson (KU Leuven (BE))

12:25 → 13:55 Lunch

13:55 → 15:30 Miscellaneous science

Convener: Dr Juliana Schell (Experimentalphysik, Universität des Saarlandes, Germany)

13:55 **On the Syntheses of ⁵⁷Mn Compounds for the Moessbauer Researches**

⁵⁷Mn emission Moessbauer spectroscopy has been known since 1975, when Preston and Zabransky published the first paper [1]. They applied the nuclear reaction ⁵⁴Cr(α,p)⁵⁷Mn to synthesize the source of ⁵⁷Mn in Cr₂O₃ matrix. In 1992 Nakada et al. [2] used the same reaction to get the sources from metallic chromium, Cr₂O₃ and CrO₃. Later, the alternative approach for producing the ⁵⁷Mn sources by ion-implantation of ⁵⁷Mn into substance was developed in ISOLDE [3] and RIKEN [4].

The peculiarity of these two approaches is the complicated chemistry which accompanies the stabilization of ⁵⁷Mn ions after ⁵⁴Cr decay or the stabilization of ⁵⁷Mn ions braking in the target as well as the radiolysis of the substance. The half-life time of ⁵⁷Mn is quite short (85 s). Therefore, it is difficult to conduct the common chemical synthesis with it. However, such a synthesis could be realized using convincing chemical reactions.

The simplest way to involve manganese into chemical reaction is to heat-up the target. This approach was already applied for several matrices. But the spectra obtained are commonly quite complicated due to the presence of several forms of ⁵⁷Fe, magnetic effects being also observed. This is due to the nature of the matrices, in particular, their low chemical activity.

We believe that the use of chemically active matrices is a way to the synthesis of ⁵⁷Mn-doped compounds containing manganese in wide range of oxidation states. We would offer several reactions which were already used by us to synthesize the compounds of ⁵⁷Fe and ⁵⁷Co [5-9].

The first type of the reactions, which could be tested is the oxidation of ⁵⁷Mn in the matrix of alkali metals peroxides or superoxides (MO_x). These oxides contain active oxygen which allows one to oxidize manganese at moderate heating [5,6]. According to manganese chemistry such interactions lead to manganese(IV), (V) and (VI). To make such tests ⁵⁷Mn can be implanted into the powder or the melt of MO_x. Then, the short-time heating should be quickly done to transform manganese into MnO₄^n--ions, n=2,3,4. In spite of high chemical activity of the peroxides and superoxides, many of them are melted at high temperatures and stable when melting. The oxidation of the transition metal takes place locally. Thus, the reactions can be cyclically repeated with the same target.

The second type is the reactions with the mixture of alkali metal peroxides or superoxides and transition metals (metal powder, oxides, etc.) [3-5]. In this case, the chemical behavior of implanted ⁵⁷Mn is determined by the matrix of the synthesizing metallates (chromates, manganates, ferrates, cobaltates, etc.). But to repeat the synthesis one should use fresh mixture.

The above mentioned reactions are greatly exothermic. The interactions are self-sustaining and less sensitive to the temperature profile in the reaction zone. The irradiation by light can be effectively used to initiate the interactions. This should noticeably simplify the experimental set-up. In particular, it allows one to use different zones of one target sequentially for the implantation and the heating.

The formation of manganate-ions (⁵⁷MnO₄^n-) could be used for Moessbauer observation of Fe⁷⁺. Indeed, it is well-known that the proper acidification of the substrate containing MnO₄^n--ions leads to disproportionation of manganese:

5 MnO₄^n- + 8(n-1) H⁺ → (6-n) MnO₄^- + (n-1) Mn²⁺ + 4(n-1) H₂O

The respective study of ⁵⁷Co and ⁵⁷Fe with the dissolution in alkali media was already performed by us [10]. But instead of iron and cobalt reduced in acidic media, manganese can easily transform to septavalent state.

We consider also the third type of the reactions where ⁵⁷Mn could be implanted into a stable at high temperature easily melting but relatively inert substance of simple composition, e.g. into V₂O₅ [8,9]. In this case, any defects can be eliminated by melting. Then, the chemical behavior of manganese is determined by crystallizing melt. This synthesis can be also performed repeatedly with one target.

References:

1. R.S.Preston and B.J.Zabransky, Physics Lett. 1975, V.55A (3), p.179-180.

2. M.Nakada et al., Bull. Chem. Soc. Jpn. 1992, V.65, p.1-5.

3. V.N.Fedoseyev et al., Nucl. Instrum. Methods Phys. Res. B 1997, V.126, 88-91.

4. Y.Yoshida, Hyp. Int. 1998, V.113, p.183-198.

5. S.K.Dedushenko et al., J.Alloys Compd. 1997, V.262-263, p.78-80.

6. S.K.Dedushenko et al., Radiochemistry 1998, V.40 (5), p.416-419.

7. S.K.Dedushenko et al., Hyp. Int. 2008, V.185, p.197-202.

8. S.K.Dedushenko and Yu.D.Perfiliev, Bull. Rus. Acad. Sci. Physics 2001, V.65 (7), p.1125-1128.

9. S.K.Dedushenko et al., Radiochemistry 2014, V.56 (5), p.481-485.

10. L.A.Kulikov et al., J. Phys. Chem. Solids 1995, V.56 (8), p. 1089-1094.

Speaker: Dr Sergey Dedushenko (-)

14:25 Boron Nitrate

I will describe the results obtained in BN from 2015 (In beam) and 2016 (Mn beam)

Speaker: Deena Naidoo (University of the Witwatersrand)

14:40 LiNbO3 & LaTaO3

Data obtained in 2015 and 2016

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

14:50 WC_Co

Speaker: Deena Naidoo (University of the Witwatersrand)

15:00 Titanium nitride: Overview of the material and the emission Mössbauer spectroscopy results

Titanium nitride (TiN) belongs to the transition metal nitrides exhibiting metallic behavior in the visible and near-IR ranges, chemical stability, high melting temperature, and tunable optical properties. As an extremely hard material with high thermal and chemical stability, low electrical and thermal resistivity, TiN thin films have found many applications in the microelectronics industry. They have also been proposed as a promising alternative plasmonic material.

TiN thin films can be synthesized by many different deposition methods. Magnetron sputtering has been proved to be a successful technique and promoted to an industrial scale for many years. Especially, the recent version of high-power impulse magnetron sputtering (HiPIMS) makes the growth of high density, metallic-like ultra-thin TiN at room temperature possible. Perfect TiN possesses face centered cubic structure. However, non-stoichiometry and possible structural defects may exist in the TiN thin films grown by magnetron sputtering. Recently, a unique static magnetic and dynamic electromagnetic behavior in TiN/C composites driven by defect engineering was reported.

In this presentation, we employed emission Mössbauer Spectroscopy (e-MS) following implantation of 57Mn to study TiN thin films prepared with magnetron sputtering. The high sensitivity of this technique makes it especially useful to correlate or elucidate the possible magnetic properties owing to the structural defects or non-stoichiometry of the as-grown TiN thin film.

Speaker: Bingcui Qi (Univ. Iceland)

15:20 Implantation in water and historical books

Speaker: Torben Esmann Molholt (CERN)

15:30 → 15:50 Coffee

15:50 → 17:05 Manganese based alloys

Convener: Valerie Augustyns (K)

15:50 MnSi status and general status of IS578

Speakers: Haraldur Pall Gunnlaugsson (KU Leuven (BE)), Roberto Mantovan

15:55 Heulser alloys and status

Speaker: Iraultza Unzueta Solozabal (Universidad del País Vasco / Euskal Herriko Unibertsitatea (ES))

16:15 Results in GaxMn

Speakers: Haraldur Pall Gunnlaugsson (KU Leuven (BE)), Torben Esmann Molholt (CERN)

16:25 Thinking break

16:30 Practice talk?

Speaker: Torben Esmann Molholt (CERN)

Saturday 2 July

09:00 → 10:50 Oxides

Convener: Torben Esmann Molholt (CERN)

09:00 Ar and C implanted ZnO

Overview of data obtained in Ar and C implanted ZnO

Speaker: Krish Bharuth-Ram

09:20 Quenching in MgO and Al2O3

Results from quenching experiments in MgO and Al2O3, comparison with resutls and interpretations from spectral series

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

09:40 Fe implanted ZnO

Description of data obtained and comparison with litterature

Speaker: Hilary Masenda (University of Witwatersrand)

09:55 Vanadium oxides: Overview of the material and the emission Mössbauer spectroscopy results

Vanadium oxides belong to the strongly correlated transition metal oxides exhibiting diverse temperature-dependent electronic, magnetic, and catalytic properties. They have wide potential applications in temperature sensors, optical and electronic devices and catalysts.

A large variety of the vanadium oxide phases have been reported, including VO (rocksalt structure),V2O3 (corundum),VO2 (rutile),V2O5 (layered orthorhombic), and Magneli phases, the homogeneous series of VnO2n-1 (3 ≤ n ≤ 9) which can be considered as intermediate structures between the end members VO2 (n →∞) and V2O3 (n = 2). Depending on a change of a thermodynamic parameter (such as pressure and temperature), or with variation in phase composition, phase transformations between these oxides can occur, which may lead to. With the exception of one Magneli phase (V7O13) and the highest-valence vanadium oxide (V2O5), most of the vanadium oxides undergo metal-insulator transitions (MITs) as functions of temperature. These complex structural and electronic transformations may involve the formation of mixed valence phases. The determination of cation oxidation state and site distribution in mixed metal oxides may be difficult in cases in which the cations exhibit variable valency.

In this presentation, we report the emission Mössbauer Spectroscopy (e-MS) measurements following implantation of 57Mn on the VO2 and V2O3 thin films prepared under different growth conditions with magnetron sputtering. The technique combines Coulomb excitation of the Mössbauer-active state with the recoil implantation of the excited atom. It has the high sensitivity and allows working at low and high temperatures to probe the temperature-induced phase changes in the VO2 and V2O3 thin films.

Speakers: Bingcui Qi (Univ. Iceland), Sveinn Olafsson (University of Iceland (IS))

10:10 YAG YIG GGG

Comparison between the materials and main results

Speaker: Petko Krastev (Bulgarian Academy of Sciences (BG))

presentation_YAG,YIG,GGG_pk4.pdf

presentation_YAG,YIG,GGG_pk4.pptx

10:30 Fe damage in ZnO

Characteristics of damage in ZnO compared to RBS data

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

10:50 → 11:10 Coffee

11:10 → 12:55 MoOx

Convener: Hilary Masenda (University of Witwatersrand)

11:10 Mo oxides studied by means of Mössbauer and Perturbed Angular Correlation Techniques

Using Perturbed Angular Correlations (PAC) and emission Mössbauer (eMS) techniques it is possible to measure hyperfine electric and magnetic fields in the material, even with very small concentrations of the implanted probes (ppm). The techniques, using exotic beams available at ISOLDE, lend itself to studying Molybdenum oxides since, due to these small concentrations, the underlying structure of the system under investigation is essentially unaltered and an unambiguous picture of physical processes can be obtained. In comparison to transition-metal oxides, the Molybdenum oxide compounds are particularly attractive due to the 2 D structure and to the ability of the molybdenum ion to change its oxidation state. When the probe atoms are located on substitutional Cd sites, after annealing at 450°C, the residual detrimental effects from ion implantation are minimal not disturbing the study of the component of interest. The PAC data show evidence for Cd occupying regular sites of the MoO3 lattice. Two EFGs are observed and the fraction of probes interacting with EFG1/EFG2 increase/decrease as a function of measuring temperature. This behaviour hints to the activation of an electronic localized state at the Cd dopant, as a function of temperature to be further investigated.

Speaker: Dr Juliana Schell (Experimentalphysik, Universität des Saarlandes, Germany)

11:40 MoOx, Mn beam

Overview of results obtained with Mn beam

Speaker: Aitana Tarzaga (JKU, Linz, Austria)

12:00 MoOx, In beam

Overview of results obtained with In beam

Speaker: Aitana Tarzaga (JKU, Linz, Austria)

12:20 MoOx, flakes

Overview of results obtained with Mn beam on MoOx single crystals

Speaker: Aitana Tarzaga (JKU, Linz, Austria)

12:35 MoS2

Results obtained on MoS2

Speaker: Torben Esmann Molholt (CERN)

12:55 → 14:25 Lunch

14:25 → 15:55 Silicon

Convener: Krish Bharuth-Ram

14:25 Overview of Silicon and the silicon part of IS501

I will give an overview of the results obtained in silicon from the 1990's and the IS501 experiment

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

14:45 Data obtained in the 501 expeirment and analysis

Speaker: Deena Naidoo (University of the Witwatersrand)

15:05 In implanted silicon and group IV's and quenching in silicon

General results obtained after implantation of 119In in group IV semiconductors together with quenching data from 2016

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

15:25 Quenching experiments with Mn in silicon

Speaker: Deena Naidoo (University of the Witwatersrand)

15:40 Discussion: Future in silicon

We will discuss the consequences of the data obtained in 2016 and the next steps

Speakers: Deena Naidoo (University of the Witwatersrand), Haraldur Pall Gunnlaugsson (KU Leuven (BE))

15:55 → 16:15 Coffee

16:15 → 17:25 Future?

Convener: Sergey Dedushenko

16:15 BMBF application and future possibilites

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

16:25 Nanocrystalline materials: Possibilities

I will give a brief introduction to nanocrystalline alloys

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

16:35 Test results in nanocrystallline material

Data obtained in 2016 and can this be used for future proposal

Speaker: Torben Esmann Molholt (CERN)

16:50 Experimental updates

What can be done better, what is needed, and who is going to do it

Speaker: Haraldur Pall Gunnlaugsson (KU Leuven (BE))

17:10 Concluding remarks

19:00 → 21:00 Workshop dinner

We will find a good restaurant in the center of Leuven