STSM reports 1 year

Michaela Altmeyer

Home Institution: ITP, University Frankfurt, Germany

Host Institution: CNR-SPIN, L´Aquila, Italy

STSM period: 07-02-2015/14-02-2015

Brief Summary of the STSM activity:

During the STSM there has been an extensive exchange about recent results concerning both the Rashba effect and ferroelectricity. On the basis of a group seminar the grantee presented work of the Frankfurt group on SrTiO3 surfaces, in which the interplay of magnetism and Rashba coupling is believed to play an important role to explain recent experimental observations.

In the framework of a group-internal workshop the members of the host institution introduced the grantee to the calculation of polarization in ferroelectric materials.

Moreover there were many interesting debates about the interplay of ferroelectricity and Rashba coupling and possible new projects for collaborations combining the expertise of both groups were discussed.

Impact: Poster presentation at the KITP conference on “New Phases and Emergent Phenomena in Correlated Materials with Strong Spin-Orbit Coupling”, Talk at the 2015 DPG Frühjahrstagung

Eleni Aza

Home Institution:Institute of Electronic Structure and Laser, Foundation for Research and Technology Heraklion, Greece

Host Institution: Department of Physics, The University of Warwick

STSM period: 2015-02-09 to 2015-03-22

Brief Summary of STSM activity:

Within the framework of the STSM during the first Grant period in the laboratories of the University of Warwick’ Physics Department and under the guidance of my host Prof G. Balakrishnan, an actual opportunity was offered for the implementation of almost all aspects of the initially suggested work plan.

Training was obtained on the fundamentals of crystal growth involving different techniques for the production of high quality crystals while the focus was put on the Floating zone technique using optical furnaces of different characteristics and the Flux method for the purposes of crystal growth of frustrated 2D magnetic systems. Starting from two different polymorphs of our 2D Manganese oxide system, we obtained mm to cm sized crystals using both floating zone & flux method. X-ray diffraction (XRD) facilities (Laue method for single crystals and Bragg-Brentano for powders) were utilized as well as SEM / EDX for the basic characterization of the first crystals that confirm the single crystal structure of the products.

Impact: The promising results from this short term visit are encouraging to further pursuit and optimize the production of quality crystals of this system in close collaboration with the Host Institution and combine it with subsequent variable-field ME characterisation at the home Institution and foreseen joint beam time applications at large-scale facilities (e.g. ISIS for neutron diffraction and DIAMOND for RIXS work).

Wojciech Brzezicki

Home Institution: CNR-SPIN Salerno, Italy

Host Institution: Jagiellonian University, Krakow, Poland

STSM period: 2015-03-27 to 2015-04-09

Brief Summary of STSM activity:

The approaches to the novel and highly non-trivial problem of the hybrid oxides, the 3d-doped 4d oxides and others were discussed with prof. Andrzej M. Oleś and his research group based on a seminar that was given by the STMS Grantee. A concept of a new publication was developed, being a valuable extension of our common PRX paper from this year, where a non-homogeneous superexchange model derived for a Mn-doped single layer ruthenate was solved. New results were obtained for a doping concentration that was not discussed in this paper, which is x=1/4 and he resolved the question of doubling of the unit cell.

Impact: Publication: W. Brzezicki, M. Cuoco and A. M. Oleś, “Novel Spin-Orbital Phases Induced by Orbital Dilution”, Journal of Superconductivity and Novel Magnetism, in press, arXiv:1506.07048.

Collaboration: This mission strengthen collaboration between my group at the Jagiellonian University in Kraków and the group of Dr. Mario Cuoco in CNR-SPIN Institute in Salerno.

Monica Buriel

web report not yet submitted

Greta Dellea

Home Institution: Politecnico di Milano – (IT)

Host Institution: ESRF – (FR)

STSM period: 01.02.2015 / 31.03.2015

Brief Summary of STSM activity:

At present, the scientific output of resonant inelastic x-ray scattering (RIXS) is reaching its limits mainly due to technical limitations in therms of energy resolution, signal intensity and sample control. In order to overcome these limitations, the new European-RIXS instrument at the new ID32 beamline of the ESRF has been designed.

The main goal of this STSM was the commissioning and performancies characterization of this new high resolution RIXS spectrometer, working in the regime of soft x-rays, for studies of electronic structure and magnetism in transition-metal-oxide. The work has been developed in strong collaboration between the beamline staff and my group in Milano. Beamline and spectrometer performances have been tested and sets of spectra in real experimental conditions have been acquired at different absorption edges (i.e. Ni-L3, Mn-L3, Ti-L3, Ce-M5, Gd-M5). The instrument, which now holds the world record of resolving power with a total instrumental resolution of 55 meV at Cu-L3 edge (930 eV), is now ready for the first users experiments run.

Impact: Measurements on different samples and at different absorption edges, as well as an optimization of the actual spectrometer performances are already planned for the future months. This will be also done in the framework of a long term proposal presented by Prof. Ghiringhelli and co-authors.

The work done during my STSM has been presented as an oral contribution at the FisMat2015 conference hold in Palermo September 28 – October 2, 2015.

Rosalba Fittipaldi

Home Institution: CNR SPIN UOS Salerno, Italy


STSM period: 20-02-2015 / 27-02-2015

Brief Summary of STSM activity:

The most important result of the short term mobility visit is the starting of a collaboration between home and host institution based on the characterization of eutectic crystals, synthesized by Prof. Pawlak’s group, via the scanning electron microscope with nano-manipulators available in the Musa group of the CNR-SPIN institute in Salerno. In particular the current-voltage measurements may be performed on the Bi2O3-Ag and GdCrO3-Gd2Oeutectics to shed light on the mechanism taking place at the interface between the phases solidified in these eutectic compounds.

During the short term mobility visit another interesting subject of study came out, i.e. the possibility to explore the optical behaviour of Sr based ruthenates crystals available in Salerno as possible metamaterials with a negative refractive index.

Impact: A new collaboration has been promoted.

Alessandro Leveratto

Home Institution: CNR-SPIN, Genova

Host Institution: TU Delft, Kavli Institute, Caviglia LAB

STSM period: 15-02-2015/28-02-2015

Brief Summary of STSM activity:

The starting purpose was to explore the low dimensional system ZnO/Zn1-xMgxO thanks to TU Delft robust support, with advanced nanolithography, for the realization of nanodevices and low-T transport measurements down to 40mK. During the STSM, before the nanodevice fabrication, sub-mm samples have been prepared and characterized by the applicant at high magnetic field, performing electric transport measurements showing quantum effects (QHE). Reducing spatially the 2DEG (0D-1D) required a tough fabrication process. The most critical situation has been the Ar-dry etching that generated a large amount of oxygen vacancies that turned partially the ZnO film/substrate into a metallic state. This added a parallel resistance contribute to the 2DEG and moreover a cross-talking among the many Hall bars realized. 2DEG has shown a high robustness, which was not obvious, to many fabrication processes. The preliminary obtained results are satisfactory and it has been shown that e-beam lithography can successfully be applied to ZnO based heterostructures.

Impact: Home and Host Institutions are still working together on the project about ZnO heterostructures. However, to obtain publishable results, a further step towards miniaturization and nanodevice realization must be done. The applicant and the Host institution already agreed further visits in order to achieve this goal. A successful realization of nanometric FET could lead to publications on high impact journals, being all such experiments not performed yet by anybody.

Nicola Maraviglia

Home Institution: Università Federico II di Napoli, IT

Host Institution: Technical University of Denmark, DK

STSM period: 28-04-2015 / 10-05-2015

Brief Summary of the STSM activity:

The new deposition chamber available in the DTU labs was successfully employed to deposit thin films of Al203 in crystalline phase upon SrTiO3 substrates by using the pulsed deposition technique. As reported by previous researches, this kind of device shows conductivity properties close to the interface between the two materials that are otherwise insulating. Furthermore, an innovative way for monitoring the film growth was tested.

The first part of the work consisted in the setting up of the electronic part that allowed for in-situ measurements of the conductivity of the samples during the deposition itself. The films were then deposited while recording the conductivity and this led to the estimation of the different contributions to the overall transport properties.

The UV light coming from the plume is able to induce photoconductivity in the bare substrate; the conductivity has a rapid increase when the thickness reaches overpass 1 nm and saturates at around 1.5 nm known as critical thickness. RHEED analysis stated the crystallinity of the deposited film

Davide Peddis

Home Institution: ISM‐CNT

Host Institution: Uppsala University

STSM period: 23/02/2015 – 23/03/2015

Summary of the STSM activity:

During the stay of Davide Peddis in Uppsala University, magnetic properties of two kinds of nanocomposites of transition metal oxides (called N‐MIX and NC sample in the following) have been investigated and discussed; each one comprises nanoparticles of La0.67Ca0.33MnO3 and CoFe2O4 in similar volume fractions, however arranged with different morphology. Magnetization dynamics have been investigated by performing magnetization measurements in different applied fields, as a function of temperature and time. Reversal mechanism of the magnetization have been studied by remanent magnetization measurements (IRM and DCD protocols). Some additional measurements have been carried to investigate the non‐equilibrium dynamics of magnetization (i.e. memory experiment with different protocols) in MnFe2O4 nanoparticles and Fe nanoparticles embedded in Cr matric (Fe@Cr). As indicated in the proposal, an intense dissemination of scientific results has been done


Designing new manganite/ferrite nanocomposites with tunable magnetic and electrical properties G. Muscas, P. Anil Kumar, G. Barucca, G. Concas, G. Varvaro, R. Mathieu and D. Peddis

Poster Communication to : International Conference on magnetism – Barcelona, July 5‐10 2015


D. Peddis*, M.T. Qureshi, S.H. Baker, C. Binns, M. Roy, S. Laureti, D. Fiorani, P. Nordblad & R. Mathieu Magnetic anisotropy and magnetization dynamics of Fe nanoparticles embedded in Cr and Ag matrices, Philosophical Magazine, 1, 10, 6435, 2015

Designing new manganite/ferrite nanocomposites G. Muscas, P. Anil Kumar, G. Barucca, G. Concas, G. Varvaro, R. Mathieu* and D. Peddis* Nanoscale 2015, In Press

Aleksandr Petrov

Home Institution: IOM-CNR Trieste, IT

Host Institution: University of Tuebingen, DE

STSM period: 02.03.2015 / 27.03.2015

Brief Summary of the STSM activity:

The idea of the research work is the study of interaction on the ferroelectric/ferromagnetic interface. Like ferromagnetic and ferroelectric were choose La1-xSrxMnO3 (LSMO) and BaTiO3 (BTO), respectively. The ferroelectric polarization with the density 0.3 C/m2 for BTO lead to the electric field screening in the interfacial layers of ferroelectric. This charge carriers change due to the screening, due to complex phase diagram of manganites, could result not only in the film resistance change but also in the LSMO magnetic order change. Like in the case of sample doped with the values close to FM-AFM phase boundary (x=0.5 for bulk). Epitaxial // LSMO heterostructures with different doping level x of the LSMO top layer and a ferroelectric BTO barrier were grown bv MBE. Afterward optical lithography combined with Ar ion milling were performed to obtain separated trilayer capacitor devices of different dimensions on each chip (SrTiO3 substrate). For measurements of ferroelectric polarization of the BTO barrier and for electric transport measurements, bottom and top LSMO electrodes have been electrically contacted. The samples were mounted on a He-gas flow cryostat for measurements down to law temperatures (∼5 K). For each device, the ferroelectric polarization current was measured, in order to check the capacitor characteristics, like polarization density and leakage current. Subsquentely, for good devices resistivity vs temperature was measured with and without externally applied magnetic field, and the resistivity in remnant polarization and in static polarization at different temperatures has been determined. Magneto-optical Kerr effect mapping was done for the top ferromagnetic LSMO layer at temperatures below the Curie temperature.

The work is continuing yet and no results were publicated or presented in conference yet.

Mantas Simenas

Mantas Simenas

Home Institution: Vilnius University, Faculty of Physics

Host Institution: Leipzig University, Faculty of Physics and Earth Sciences

STSM period: 23-02-2015/01-03-2015

Brief Summary of the STSM activity:

The continuous wave (CW) and pulse EPR methods were successfully applied to investigate the structural phase transition in [(CH3)2NH2][Zn(HCOO)3] metal-organic framework (MOF) powder sample doped withMn2+ ions. A sudden change in the X- and Q-band CW and two-pulse field-sweep EPR spectra was observed at 160K temperature, which corresponds to the structural phase transition temperature in the investigated MOF. This indicates that the Mn2+ ions successfully replaced Zn2+ ion species in the framework allowing observation of the local changes of the Mn2+ coordination environment at the phase transition point.

Publications: EPR Study of Structural Phase Transition in Manganese Doped [(CH3)2NH2][Zn(HCOO)3] metal-organic framework, submitted to the Journal of Physical Chemistry C

Brief Summary of the STSM activity:

The STSM provided an ideal opportunity for extended discussions on recent results obtained about the influence of flexoelectricity in centerosymmetric and non centerosymmetric crystals. Additionally the STSM provided an understanding of the experimental capabilities and competencies of the host institution and fostered discussion about future collaboration projects

Impact: The visit facilitated discussion of ideas and the identification of challenges hindering their pursuit. However, to obtain publishable results, extensive work has to be made for the fabrication and characterization of the proposed devices

Emiliano Di Gennaro

Home Institution: Università di Napoli Federico II, Napoli , Italy

Host Institution: Swiss Light Source Paul Scherrer Institut, Switzerland

STSM period: 2016-10-22/2016-10-28

Brief Summary of the STSM activity:

The goal of the collaboration was to determine the nature of the interface states near the Fermi surface of LAO/ETO/STO and ETO/STO heterostructures and the Eu-4f, and in case Eu-5d states contribution to the conduction band of the spin-polarized 2DEG. With this aim, we fabricated ETO films in with different thicknesses on STO substrates at SIS beamline, by RHEED assisted PLD; then, we performed, in-situ, ARPES measurements at the HRPES station and spin-resolved ARPES at the COPHEE station. Instead to investigate the band structure and the orbital character of the electronically reconstructed LaAlO3/EuTiO3/SrTiO3 heterostructure fabricated in Naples, we used resonant soft x-ray angle resolved photoemission spectroscopy


Compared to STO and LAO/STO, ETO and LAO/ETO/STO are system much less studied. As a consequence, the results we obtained in these measurements runs are of great interest and surely innovative, deserving high level publications.

We foresee to quickly publish the results obtained by resonant soft x-rays ARPES, which allow a relatively more immediate analysis. A first publication will concerns the fundamental spectroscopic features that we measured, and their comparison with the well known features of STO. Then, possibly, a second important output can come from the polaronic character of the interface states, if confirmed.

The measurements at High Resolution ARPES beamline will complement this study, allowing a detailed description of the ETO bands and Fermi surface, on which there are currently not a full knowledge. Finally, a further publication could come from the spin-resolved ARPES data, if the related analysis will furnish a complete picture.