The contribution of the CNR research unit in Trieste is based on the experimental support of the TASC-INFM-CNR National Laboratory, an infrastructure historically active in the research with synchrotron radiation. Such a Laboratory is involved in the activities at the ELETTRA synchrotron radiation facility where it manages six synchrotron radiation beamlines. These apparatuses are available to the unit components as well as to other units participating to the project. The TASC-INFM-CNR group involved in the PRIN project, mainly operating at the ALOISA beamline, has a deep-rooted capability in the study of low dimensional systems by means of photoelectron spectroscopies and photoelectron and photon diffraction and, in particular, they are a reference group for the electron-electron coincidence spectroscopy (APECS) from solids. With respect to the magnetic dichroism measured in the more conventional single particle spectroscopies (like absorption and photoemission), the line shape of core-valence-valence Auger decays, whose final state is at least a two hole one, has got intrinsically information on the electronic correlation in the valence band. If measured in coincidence with the parent photoelectron emission, it has got a further selectivity on the local environment and on the emission depth. Such an added value will be joined with the magnetic dichroism effect which has been recently discovered by the Trieste and Roma3 groups (DEAR-APECS), thank to the availability of polarized radiation supplied by the synchrotron source. The ID8 Dragon beamline at ESRF in Grenoble and the BL U49-2_PGM-1 beamline - End Station PHOENEXS - at Bessy in Berlin will be considered for the spin resolved measurements for the ejected Auger electrons. One of the research scientists which is integral part of the CNR unit is employed in the IFN-CNR institute in Rome. Indeed he operates in the laboratories of the Roma Tre University, in the group which constitutes the Roma Tre Unit. He will act as an effective joining between the Rome units and the experimental support in Trieste. Taking into account the capabilities of the TASC-INFM-CNR, the Trieste unit will give the experimental support to carry out the planned synchrotron radiation experimental program: 1.Ni/Cu(100) measurements on ALOISA: - APECS on the MVV Auger line at energy resolution not limited by the core hole lifetime broadening and DEAR-APECS crossing the magnetic ordering transition as a function of the thickness and/or the temperature. - DEAR-APECS switching the magnetization by means of a coercive field parallel to the surface, analogously to which is performed to detect the LMDAD (Linear Magnetic Dichroism in the Angular Distribution); comparison with spin resolved Auger spectra - AES/APECS measurements in the sub-monolayer regime in order to test the calculations for magnetic impurities diluted in simple metals already developed by the Milano Bicocca group. 2. NiO/Ag(001) a antiferromagnetic system (AFM): measurements DEAR-APECS above and below the Neèl transition temperature in order to confirm the navel and huge magnetic dichroism effect observed on the analogous CoO/Ag(001) system. 3. Fe islands on Cu3Au(001) whose magnetic properties depend upon the size of the islands: Auger line shape measurements on ALOISA by AES/APECS in order to highlight effects due to the size of the islands and to the interface; eventual comparison with spin resolved Auger spectra. 4. Eventual DEAR-APECS measurements on Fe(x)Co(1-x) monolayers on Pt(111) in order to see how the Auger line shape and its magnetic dichroism are affected, with respect to the bulk alloys, by a system characterized by a high magnetic anisotropy accompanied with a low average saturation magnetization, an effect induced by the reduced dimensionality. We also plan the implementation of a magnetization stage on the sample holder of the ALOISA end-station realized and tested by the Roma Tre Unit.
Il contributo dell'unità di ricerca di Trieste del CNR è fondato sul supporto sperimentale fornito dal Laboratorio Nazionale TASC-INFM-CNR, un'infrastruttura storicamente attiva nella fisica della materia mediante l'utilizzo della Radiazione di Sincrotrone. Tale Laboratorio è coinvolto nelle attività di ricerca scientifica presso il Sincrotrone ELETTRA di Trieste, dove gestisce sei Linee di luce di sincrotrone (beamlines). L'accesso a questi apparati è aperto sia ai componenti dell'unità CNR, sia a quelli delle altre unità partecipanti al presente progetto. Il gruppo del TASC-INFM-CNR coinvolto nel PRIN opera principalmente sulla linea ALOISA ed ha radicate competenze nell'ambito degli studi dei sistemi a bassa dimensionalità attraverso l'indagine mediante spettroscopie elettroniche e tecniche di diffrazione sia di fotoelettroni che di fotoni. In particolare, tale gruppo costituisce un riferimento per le spettroscopie in coincidenza elettrone-elettrone APECS (Auger PhotoElectron Coincidence Spectroscopy) da solidi. Rispetto alle misure di dicroismo magnetico nelle più convenzionali spettroscopie a singola particella (quali assorbimento e fotoemissione), la forma di riga di decadimenti Auger core-valenza-valenza, il cui stato finale è almeno a due lacune, possiede intrinsecamente informazioni sulla correlazione elettronica in banda di valenza. Se misurata in coincidenza con il fotoelettrone progenitore, possiede inoltre selettività sull'ambiente locale e sulla profondità di emissione. Tale valore aggiunto della spettroscopia Auger verrà combinato con l'effetto di dicroismo magnetico recentemente scoperto dai gruppi di Trieste e Roma3 (DEAR-APECS), reso possibile grazie all'utilizzo della radiazione polarizzata prodotta dalla sorgente di sincrotrone. Per quanto concerne le misure di elettroni Auger risolte in spin, si farà riferimento alle beamline ID8 Dragon di ESRF a Grenoble e BL U49-2_PGM-1 End Station PHOENEXS di Bessy a Berlino. Fa parte integrante dell'unità CNR anche un ricercatore dell'Istituto IFN di Roma che, di fatto, opera presso i laboratori dell'Università di Roma Tre nel gruppo che costituisce l'unità di Roma Tre. Egli costituirà pertanto un efficace anello di congiunzione tra le due unità. Facendo riferimento alle potenzialità del laboratorio TASC-INFM-CNR, l'unità di Trieste fornirà il supporto sperimentale al fine di attuare il seguente programma di esperimenti con radiazione di sincrotrone: 1. Ni/Cu(100) misure su ALOISA: - APECS delle righe MVV con risoluzione energetica non limitata dal tempo di vita media della buca e DEAR-APECS attraversando la transizione di ordine magnetico in funzione dello spessore e/o della temperatura - DEAR-APECS invertendo la magnetizzazione con un campo coercitivo parallelo alla superficie in analogia a quanto si fa per il dicroismo magnetico lineare osservato nella distribuzione angolare: LMDAD (Linear Magnetic Dichroism in the Angular Distribution); confronto con spettri Auger risolti in spin. - AES/APECS nel regime di sub-monolayer per testare la teoria per impurezze magnetiche diluite in substrato metallico già sviluppato dal gruppo di Milano Bicocca. 2. NiO/Ag(001) sistema antiferromagnetico (AFM): misure DEAR-APECS sopra e sotto la temperatura di transizione di Neèl, per confermare il grosso effetto di dicroismo magnetico riscontrato sul sistema CoO/Ag(001). 3. Isole di Fe/Cu3Au(001) i cui parametri magnetici cambiano al variare delle dimensioni delle isole: misure della forma di riga Auger su ALOISA con AES/APECS per evidenziare effetti dovuti alla dimensione delle isole e all'interfaccia; eventuale confronto con spettri Auger risolti in spin. 4. Eventuali misure DEAR-APECS su monostrati di Fe(x)Co(1-x) su Pt(111) allo scopo di vedere la ripercussione sulla forma di riga Auger e sul suo dicroismo magnetico, rispetto alle leghe di volume, di un sistema caratterizzato da un'alta anisotropia magnetica accompagnata da un bassa magnetizzazione media di saturazione, un evidente effetto indotto dalla dimensionalità ridotta. E' infine prevista l'implementazione di un sistema di magnetizzazione solidale con il porta campione per la camera sperimentale di ALOISA, realizzato e testato dall'Unità Roma Tre.
PROGETTO DI UNITÀ DI RICERCA
damjan krizmancic
2008
Abstract
The contribution of the CNR research unit in Trieste is based on the experimental support of the TASC-INFM-CNR National Laboratory, an infrastructure historically active in the research with synchrotron radiation. Such a Laboratory is involved in the activities at the ELETTRA synchrotron radiation facility where it manages six synchrotron radiation beamlines. These apparatuses are available to the unit components as well as to other units participating to the project. The TASC-INFM-CNR group involved in the PRIN project, mainly operating at the ALOISA beamline, has a deep-rooted capability in the study of low dimensional systems by means of photoelectron spectroscopies and photoelectron and photon diffraction and, in particular, they are a reference group for the electron-electron coincidence spectroscopy (APECS) from solids. With respect to the magnetic dichroism measured in the more conventional single particle spectroscopies (like absorption and photoemission), the line shape of core-valence-valence Auger decays, whose final state is at least a two hole one, has got intrinsically information on the electronic correlation in the valence band. If measured in coincidence with the parent photoelectron emission, it has got a further selectivity on the local environment and on the emission depth. Such an added value will be joined with the magnetic dichroism effect which has been recently discovered by the Trieste and Roma3 groups (DEAR-APECS), thank to the availability of polarized radiation supplied by the synchrotron source. The ID8 Dragon beamline at ESRF in Grenoble and the BL U49-2_PGM-1 beamline - End Station PHOENEXS - at Bessy in Berlin will be considered for the spin resolved measurements for the ejected Auger electrons. One of the research scientists which is integral part of the CNR unit is employed in the IFN-CNR institute in Rome. Indeed he operates in the laboratories of the Roma Tre University, in the group which constitutes the Roma Tre Unit. He will act as an effective joining between the Rome units and the experimental support in Trieste. Taking into account the capabilities of the TASC-INFM-CNR, the Trieste unit will give the experimental support to carry out the planned synchrotron radiation experimental program: 1.Ni/Cu(100) measurements on ALOISA: - APECS on the MVV Auger line at energy resolution not limited by the core hole lifetime broadening and DEAR-APECS crossing the magnetic ordering transition as a function of the thickness and/or the temperature. - DEAR-APECS switching the magnetization by means of a coercive field parallel to the surface, analogously to which is performed to detect the LMDAD (Linear Magnetic Dichroism in the Angular Distribution); comparison with spin resolved Auger spectra - AES/APECS measurements in the sub-monolayer regime in order to test the calculations for magnetic impurities diluted in simple metals already developed by the Milano Bicocca group. 2. NiO/Ag(001) a antiferromagnetic system (AFM): measurements DEAR-APECS above and below the Neèl transition temperature in order to confirm the navel and huge magnetic dichroism effect observed on the analogous CoO/Ag(001) system. 3. Fe islands on Cu3Au(001) whose magnetic properties depend upon the size of the islands: Auger line shape measurements on ALOISA by AES/APECS in order to highlight effects due to the size of the islands and to the interface; eventual comparison with spin resolved Auger spectra. 4. Eventual DEAR-APECS measurements on Fe(x)Co(1-x) monolayers on Pt(111) in order to see how the Auger line shape and its magnetic dichroism are affected, with respect to the bulk alloys, by a system characterized by a high magnetic anisotropy accompanied with a low average saturation magnetization, an effect induced by the reduced dimensionality. We also plan the implementation of a magnetization stage on the sample holder of the ALOISA end-station realized and tested by the Roma Tre Unit.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
