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1. Crossover From Individual to Collective Magnetism in Dense Nanoparticle Systems: Local Anisotropy Versus Dipolar Interactions

Author

Sánchez, Elena H., Vasilakaki, Marianna, Lee, Su Seong, Normile, Peter S., Andersson, Mikael S., Mathieu, Roland, López-Ortega, Alberto, Pichon, Benoit P., Peddis, Davide, Binns, Chris, Nordblad, Per, Trohidou, Kalliopi, Nogués, Josep, and De Toro, José A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Materials Science
Abstract

Dense systems of magnetic nanoparticles may exhibit dipolar collective behavior. However, two fundamental questions remain unsolved: i) whether the transition temperature may be affected by the particle anisotropy or it is essentially determined by the intensity of the interparticle dipolar interactions, and ii) what is the minimum ratio of dipole-dipole interaction ($E_\text{dd}$) to nanoparticle anisotropy ($K_{\text{ef}}V$, anisotropy $\times$ volume) energies necessary to crossover from individual to collective behavior. A series of particle assemblies with similarly intense dipolar interactions but widely varying anisotropy is studied. The $K_\text{ef}$ is tuned through different degrees of cobalt-doping in maghemite nanoparticles, resulting in a variation of nearly an order of magnitude. All the bare particle compacts display collective behavior, except the one made with the highest anisotropy particles, which presents ``marginal'' features. Thus, a threshold of $K_{\text{ef}} V/E_{\text{dd}} \approx 130$ to suppress collective behavior is derived, in good agreement with Monte Carlo simulations. This translates into a crossover value of $\approx 1.7$ for the easily accessible parameter $T_\text{MAX}$(interacting)$/T_\text{MAX}$(non-interacting) (ratio of the peak temperatures of the zero-field-cooled magnetization curves of interacting and dilute particle systems), which is successfully tested against the literature to predict the individual-like$/$collective behavior of any given interacting particle assembly comprising relatively uniform particles., Comment: 24 pages (proof version), 6 figures

Published
2024
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4. Probing the Meta-Stability of Oxide Core/Shell Nanoparticle Systems at Atomic Resolution

Author

Roldana, Manuel A., Mayence, Arnaud, López-Ortega, Alberto, Ishikawa, Ryo, Salafranca, Juan, Estrader, Marta, Salazar-Alvarez, German, Baró, M. Dolors, Nogués, Josep, Pennycook, Stephen J., and Varelaa, Maria

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

Hybrid nanoparticles allow exploiting the interplay of confinement, proximity between different materials and interfacial effects. However, to harness their properties an in-depth understanding of their (meta)stability and interfacial characteristics is crucial. This is especially the case of nanosystems based on functional oxides working under reducing conditions, which may severely impact their properties. In this work, the in-situ electron-induced selective reduction of Mn3O4 to MnO is studied in magnetic Fe3O4/Mn3O4 and Mn3O4/Fe3O4 core/shell nanoparticles by means of high-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Such in-situ transformation allows mimicking the actual processes in operando environments. A multi-stage image analysis using geometric phase analysis combined with particle image velocity enables direct monitoring of the relationship between structure, chemical composition and strain relaxation during the Mn3O4 reduction. In the case of Fe3O4/Mn3O4 core/shell the transformation occurs smoothly without the formation of defects. However, for the inverse Mn3O4/Fe3O4 core/shell configuration the electron beam-induced transformation occurs in different stages that include redox reactions and void formation followed by strain field relaxation via formation of defects. This study highlights the relevance of understanding the local dynamics responsible for changes in the particle composition in order to control stability and, ultimately, macroscopic functionality.

Published
2020
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5. Magnetoplasmonics in nanocavities: Dark plasmons enhance magneto-optics beyond the intrinsic limit of magnetoplasmonic nanoantennas

Author

López-Ortega, Alberto, Herrera, Mario Zapata, Maccaferri, Nicolò, Pancaldi, Matteo, Garcia, Mikel, Chuvilin, Andrey, and Vavassori, Paolo

Subjects
Physics - Optics
Abstract

Enhancing magneto-optical effects is crucial for size reduction of key photonic devices based on non-reciprocal propagation of light and to enable active nanophotonics. We disclose a so far unexplored approach that exploits dark plasmons to produce an unprecedented amplification of magneto-optical activity. We designed and fabricated non-concentric magnetoplasmonic-disk/plasmonic-ring-resonator nanocavities supporting multipolar dark modes. The broken geometrical symmetry of the design enables coupling with free-space light and hybridization of dark modes of the ring nanoresonator with the dipolar localized plasmon resonance of the magnetoplasmonic disk. Such hybridization generates a multipolar resonance that amplifies the magneto-optical response of the nanocavity by ~1-order of magnitude with respect to the maximum enhancement achievable by localized plasmons in bare magnetoplasmonic nanoantennas. This large amplification results from the peculiar and enhanced electrodynamic response of the nanocavity, yielding an intense magnetically-activated radiant magneto-optical dipole driven by the low-radiant multipolar resonance. The concept proposed is general and, therefore, our results open a new path that can revitalize research and applications of magnetoplasmonics to active nanophotonics and flat optics., Comment: Supplementary Information included

Published
2019
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8. Addressing climate change with behavioral science:A global intervention tournament in 63 countries

Author

Vlasceanu, Madalina, Doell, Kimberly C., Bak-Coleman, Joseph B., Todorova, Boryana, Berkebile-Weinberg, Michael M., Grayson, Samantha J., Patel, Yash, Goldwert, Danielle, Pei, Yifei, Chakroff, Alek, Pronizius, Ekaterina, van den Broek, Karlijn L., Vlasceanu, Denisa, Constantino, Sara, Morais, Michael J., Schumann, Philipp, Rathje, Steve, Fang, Ke, Aglioti, Salvatore Maria, Alfano, Mark, Alvarado-Yepez, Andy J., Andersen, Angélica, Anseel, Frederik, Apps, Matthew A.J., Asadli, Chillar, Awuor, Fonda Jane, Azevedo, Flavio, Basaglia, Piero, Bélanger, Jocelyn J., Berger, Sebastian, Bertin, Paul, Białek, Michał, Bialobrzeska, Olga, Blaya-Burgo, Michelle, Bleize, Daniëlle N.M., Bø, Simen, Boecker, Lea, Boggio, Paulo S., Borau, Sylvie, Bos, Björn, Bouguettaya, Ayoub, Brauer, Markus, Brick, Cameron, Brik, Tymofii, Briker, Roman, Brosch, Tobias, Buchel, Ondrej, Buonauro, Daniel, Butalia, Radhika, Carvacho, Héctor, Chamberlain, Sarah A.E., Chan, Hang Yee, Chow, Dawn, Chung, Dongil, Cian, Luca, Cohen-Eick, Noa, Contreras-Huerta, Luis Sebastian, Contu, Davide, Cristea, Vladimir, Cutler, Jo, D'Ottone, Silvana, De Keersmaecker, Jonas, Delcourt, Sarah, Delouvée, Sylvain, Diel, Kathi, Douglas, Benjamin D., Drupp, Moritz A., Dubey, Shreya, Ekmanis, Jānis, Elbaek, Christian T., Elsherif, Mahmoud, Engelhard, Iris M., Escher, Yannik A., Etienne, Tom W., Farage, Laura, Farias, Ana Rita, Feuerriegel, Stefan, Findor, Andrej, Freira, Lucia, Friese, Malte, Gains, Neil Philip, Gallyamova, Albina, Geiger, Sandra J., Genschow, Oliver, Gjoneska, Biljana, Gkinopoulos, Theofilos, Goldberg, Beth, Goldenberg, Amit, Gradidge, Sarah, Grassini, Simone, Gray, Kurt, Grelle, Sonja, Griffin, Siobhán M., Grigoryan, Lusine, Grigoryan, Ani, Grigoryev, Dmitry, Gruber, June, Guilaran, Johnrev, Hadar, Britt, Hahnel, Ulf J.J., Halperin, Eran, Harvey, Annelie J., Haugestad, Christian A.P., Herman, Aleksandra M., Hershfield, Hal E., Himichi, Toshiyuki, Hine, Donald W., Hofmann, Wilhelm, Howe, Lauren, Huaman-Chulluncuy, Enma T., Huang, Guanxiong, Ishii, Tatsunori, Ito, Ayahito, Jia, Fanli, Jost, John T., Jovanović, Veljko, Jurgiel, Dominika, Kácha, Ondřej, Kankaanpää, Reeta, Kantorowicz, Jaroslaw, Kantorowicz-Reznichenko, Elena, Kaplan Mintz, Keren, Kaya, Ilker, Kaya, Ozgur, Khachatryan, Narine, Klas, Anna, Klein, Colin, Klöckner, Christian A., Koppel, Lina, Kosachenko, Alexandra I., Kothe, Emily J., Krebs, Ruth, Krosch, Amy R., Krouwel, Andre P.M., Kyrychenko, Yara, Lagomarsino, Maria, Lamm, Claus, Lange, Florian, Lee Cunningham, Julia, Lees, Jeffrey, Leung, Tak Yan, Levy, Neil, Lockwood, Patricia L., Longoni, Chiara, López Ortega, Alberto, Loschelder, David D., Lu, Jackson G., Luo, Yu, Luomba, Joseph, Lutz, Annika E., Majer, Johann M., Markowitz, Ezra, Marsh, Abigail A., Mascarenhas, Karen Louise, Mbilingi, Bwambale, Mbungu, Winfred, McHugh, Cillian, Meijers, Marijn H.C., Mercier, Hugo, Mhagama, Fenant Laurent, Michalakis, Katerina, Mikus, Nace, Milliron, Sarah, Mitkidis, Panagiotis, Monge-Rodríguez, Fredy S., Mora, Youri L., Moreau, David, Motoki, Kosuke, Moyano, Manuel, Mus, Mathilde, Navajas, Joaquin, Nguyen, Tam Luong, Nguyen, Dung Minh, Nguyen, Trieu, Niemi, Laura, Nijssen, Sari R.R., Nilsonne, Gustav, Nitschke, Jonas P., Nockur, Laila, Okura, Ritah, Öner, Sezin, Özdoğru, Asil Ali, Palumbo, Helena, Panagopoulos, Costas, Panasiti, Maria Serena, Pärnamets, Philip, Paruzel-Czachura, Mariola, Pavlov, Yuri G., Payán-Gómez, César, Pearson, Adam R., Pereira da Costa, Leonor, Petrowsky, Hannes M., Pfattheicher, Stefan, Pham, Nhat Tan, Ponizovskiy, Vladimir, Pretus, Clara, Rêgo, Gabriel G., Reimann, Ritsaart, Rhoads, Shawn A., Riano-Moreno, Julian, Richter, Isabell, Röer, Jan Philipp, Rosa-Sullivan, Jahred, Ross, Robert M., Sabherwal, Anandita, Saito, Toshiki, Sarrasin, Oriane, Say, Nicolas, Schmid, Katharina, Schmitt, Michael T., Schoenegger, Philipp, Scholz, Christin, Schug, Mariah G., Schulreich, Stefan, Shreedhar, Ganga, Shuman, Eric, Sivan, Smadar, Sjåstad, Hallgeir, Soliman, Meikel, Soud, Katia, Spampatti, Tobia, Sparkman, Gregg, Spasovski, Ognen, Stanley, Samantha K., Stern, Jessica A., Strahm, Noel, Suko, Yasushi, Sul, Sunhae, Syropoulos, Stylianos, Taylor, Neil C., Tedaldi, Elisa, Tinghög, Gustav, Huynh, Luu Duc Toan, Travaglino, Giovanni Antonio, Tsakiris, Manos, Tüter, İlayda, Tyrala, Michael, Uluğ, Özden Melis, Urbanek, Arkadiusz, Valko, Danila, van der Linden, Sander, van Schie, Kevin, van Stekelenburg, Aart, Vanags, Edmunds, Västfjäll, Daniel, Vesely, Stepan, Vintr, Jáchym, Vranka, Marek, Wanguche, Patrick Otuo, Willer, Robb, Wojcik, Adrian Dominik, Xu, Rachel, Yadav, Anjali, Zawisza, Magdalena, Zhao, Xian, Zhao, Jiaying, Żuk, Dawid, Van Bavel, Jay J., Vlasceanu, Madalina, Doell, Kimberly C., Bak-Coleman, Joseph B., Todorova, Boryana, Berkebile-Weinberg, Michael M., Grayson, Samantha J., Patel, Yash, Goldwert, Danielle, Pei, Yifei, Chakroff, Alek, Pronizius, Ekaterina, van den Broek, Karlijn L., Vlasceanu, Denisa, Constantino, Sara, Morais, Michael J., Schumann, Philipp, Rathje, Steve, Fang, Ke, Aglioti, Salvatore Maria, Alfano, Mark, Alvarado-Yepez, Andy J., Andersen, Angélica, Anseel, Frederik, Apps, Matthew A.J., Asadli, Chillar, Awuor, Fonda Jane, Azevedo, Flavio, Basaglia, Piero, Bélanger, Jocelyn J., Berger, Sebastian, Bertin, Paul, Białek, Michał, Bialobrzeska, Olga, Blaya-Burgo, Michelle, Bleize, Daniëlle N.M., Bø, Simen, Boecker, Lea, Boggio, Paulo S., Borau, Sylvie, Bos, Björn, Bouguettaya, Ayoub, Brauer, Markus, Brick, Cameron, Brik, Tymofii, Briker, Roman, Brosch, Tobias, Buchel, Ondrej, Buonauro, Daniel, Butalia, Radhika, Carvacho, Héctor, Chamberlain, Sarah A.E., Chan, Hang Yee, Chow, Dawn, Chung, Dongil, Cian, Luca, Cohen-Eick, Noa, Contreras-Huerta, Luis Sebastian, Contu, Davide, Cristea, Vladimir, Cutler, Jo, D'Ottone, Silvana, De Keersmaecker, Jonas, Delcourt, Sarah, Delouvée, Sylvain, Diel, Kathi, Douglas, Benjamin D., Drupp, Moritz A., Dubey, Shreya, Ekmanis, Jānis, Elbaek, Christian T., Elsherif, Mahmoud, Engelhard, Iris M., Escher, Yannik A., Etienne, Tom W., Farage, Laura, Farias, Ana Rita, Feuerriegel, Stefan, Findor, Andrej, Freira, Lucia, Friese, Malte, Gains, Neil Philip, Gallyamova, Albina, Geiger, Sandra J., Genschow, Oliver, Gjoneska, Biljana, Gkinopoulos, Theofilos, Goldberg, Beth, Goldenberg, Amit, Gradidge, Sarah, Grassini, Simone, Gray, Kurt, Grelle, Sonja, Griffin, Siobhán M., Grigoryan, Lusine, Grigoryan, Ani, Grigoryev, Dmitry, Gruber, June, Guilaran, Johnrev, Hadar, Britt, Hahnel, Ulf J.J., Halperin, Eran, Harvey, Annelie J., Haugestad, Christian A.P., Herman, Aleksandra M., Hershfield, Hal E., Himichi, Toshiyuki, Hine, Donald W., Hofmann, Wilhelm, Howe, Lauren, Huaman-Chulluncuy, Enma T., Huang, Guanxiong, Ishii, Tatsunori, Ito, Ayahito, Jia, Fanli, Jost, John T., Jovanović, Veljko, Jurgiel, Dominika, Kácha, Ondřej, Kankaanpää, Reeta, Kantorowicz, Jaroslaw, Kantorowicz-Reznichenko, Elena, Kaplan Mintz, Keren, Kaya, Ilker, Kaya, Ozgur, Khachatryan, Narine, Klas, Anna, Klein, Colin, Klöckner, Christian A., Koppel, Lina, Kosachenko, Alexandra I., Kothe, Emily J., Krebs, Ruth, Krosch, Amy R., Krouwel, Andre P.M., Kyrychenko, Yara, Lagomarsino, Maria, Lamm, Claus, Lange, Florian, Lee Cunningham, Julia, Lees, Jeffrey, Leung, Tak Yan, Levy, Neil, Lockwood, Patricia L., Longoni, Chiara, López Ortega, Alberto, Loschelder, David D., Lu, Jackson G., Luo, Yu, Luomba, Joseph, Lutz, Annika E., Majer, Johann M., Markowitz, Ezra, Marsh, Abigail A., Mascarenhas, Karen Louise, Mbilingi, Bwambale, Mbungu, Winfred, McHugh, Cillian, Meijers, Marijn H.C., Mercier, Hugo, Mhagama, Fenant Laurent, Michalakis, Katerina, Mikus, Nace, Milliron, Sarah, Mitkidis, Panagiotis, Monge-Rodríguez, Fredy S., Mora, Youri L., Moreau, David, Motoki, Kosuke, Moyano, Manuel, Mus, Mathilde, Navajas, Joaquin, Nguyen, Tam Luong, Nguyen, Dung Minh, Nguyen, Trieu, Niemi, Laura, Nijssen, Sari R.R., Nilsonne, Gustav, Nitschke, Jonas P., Nockur, Laila, Okura, Ritah, Öner, Sezin, Özdoğru, Asil Ali, Palumbo, Helena, Panagopoulos, Costas, Panasiti, Maria Serena, Pärnamets, Philip, Paruzel-Czachura, Mariola, Pavlov, Yuri G., Payán-Gómez, César, Pearson, Adam R., Pereira da Costa, Leonor, Petrowsky, Hannes M., Pfattheicher, Stefan, Pham, Nhat Tan, Ponizovskiy, Vladimir, Pretus, Clara, Rêgo, Gabriel G., Reimann, Ritsaart, Rhoads, Shawn A., Riano-Moreno, Julian, Richter, Isabell, Röer, Jan Philipp, Rosa-Sullivan, Jahred, Ross, Robert M., Sabherwal, Anandita, Saito, Toshiki, Sarrasin, Oriane, Say, Nicolas, Schmid, Katharina, Schmitt, Michael T., Schoenegger, Philipp, Scholz, Christin, Schug, Mariah G., Schulreich, Stefan, Shreedhar, Ganga, Shuman, Eric, Sivan, Smadar, Sjåstad, Hallgeir, Soliman, Meikel, Soud, Katia, Spampatti, Tobia, Sparkman, Gregg, Spasovski, Ognen, Stanley, Samantha K., Stern, Jessica A., Strahm, Noel, Suko, Yasushi, Sul, Sunhae, Syropoulos, Stylianos, Taylor, Neil C., Tedaldi, Elisa, Tinghög, Gustav, Huynh, Luu Duc Toan, Travaglino, Giovanni Antonio, Tsakiris, Manos, Tüter, İlayda, Tyrala, Michael, Uluğ, Özden Melis, Urbanek, Arkadiusz, Valko, Danila, van der Linden, Sander, van Schie, Kevin, van Stekelenburg, Aart, Vanags, Edmunds, Västfjäll, Daniel, Vesely, Stepan, Vintr, Jáchym, Vranka, Marek, Wanguche, Patrick Otuo, Willer, Robb, Wojcik, Adrian Dominik, Xu, Rachel, Yadav, Anjali, Zawisza, Magdalena, Zhao, Xian, Zhao, Jiaying, Żuk, Dawid, and Van Bavel, Jay J.

Abstract

Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions' effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior-several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people's initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors.

Published
2024

9. The personality is political (especially for populists).

Author

López Ortega, Alberto

Subjects
*PERSONALITY, *POPULIST parties (Politics), *POLITICAL psychology
Abstract

Are elections becoming personality contests? A growing literature is concerned about the increasing personalization of politics and its democratic consequences. This paper argues that part of the phenomenon is due to voters using politicians' personalities to infer their party and valence and that voters of populist parties are especially able in this inferential task. Using a varying conjoint experiment in Spain, the author certainly finds evidence that the importance of personality decreases when voters learn both about candidates' party and valence and that this mediating effect is especially relevant for Vox and UP voters. These results dispel concerns about the irrationality of today's politics by showing that the independent effect of personality is minimal and suggesting that populist voters efficiently use the personality of politicians to infer classical vote determinants. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Instrumentally Inclusive: The Political Psychology of Homonationalism.

Author

TURNBULL-DUGARTE, STUART J. and LÓPEZ ORTEGA, ALBERTO

Subjects
*POLITICAL psychology, *OUTGROUPS (Social groups), *LIBERALISM, *PROVOCATION (Behavior), *CRITICAL analysis
Abstract

Can nativist attitudes condition support for LGBT+ rights? The sustained advance in pro-LGBT+ attitudes in the West often contrasts with the greening of anti-immigrant sentiment propagated by nativist supply-side actors. We argue that these parallel trends are causally connected, theorizing that exposure to sexually conservative ethnic out-groups can provoke an instrumental increase in LGBT+ inclusion, particularly among those hostile toward immigration. Leveraging experiments in Britain and Spain, we provide causal evidence that citizens strategically liberalize their levels of support for LGBT+ rights when opponents of these measures are from the ethnic out-group. In a context where sexuality-based liberalism is nationalized, increasing tolerance toward LGBT+ citizens is driven by a desire among nativist citizens to socially disidentify from those out-groups perceived as inimical to these nationalized norms. Our analyses provide a critical interpretation of positive trends in LGBT+ tolerance with instrumental liberalism masking lower rates of genuine shifts in LGBT+ inclusion. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Addressing climate change with behavioral science: A global intervention tournament in 63 countries

Author

Vlasceanu, Madalina, primary, Doell, Kimberly C., additional, Bak-Coleman, Joseph B., additional, Todorova, Boryana, additional, Berkebile-Weinberg, Michael M., additional, Grayson, Samantha J., additional, Patel, Yash, additional, Goldwert, Danielle, additional, Pei, Yifei, additional, Chakroff, Alek, additional, Pronizius, Ekaterina, additional, van den Broek, Karlijn L., additional, Vlasceanu, Denisa, additional, Constantino, Sara, additional, Morais, Michael J., additional, Schumann, Philipp, additional, Rathje, Steve, additional, Fang, Ke, additional, Aglioti, Salvatore Maria, additional, Alfano, Mark, additional, Alvarado-Yepez, Andy J., additional, Andersen, Angélica, additional, Anseel, Frederik, additional, Apps, Matthew A. J., additional, Asadli, Chillar, additional, Awuor, Fonda Jane, additional, Azevedo, Flavio, additional, Basaglia, Piero, additional, Bélanger, Jocelyn J., additional, Berger, Sebastian, additional, Bertin, Paul, additional, Białek, Michał, additional, Bialobrzeska, Olga, additional, Blaya-Burgo, Michelle, additional, Bleize, Daniëlle N. M., additional, Bø, Simen, additional, Boecker, Lea, additional, Boggio, Paulo S., additional, Borau, Sylvie, additional, Bos, Björn, additional, Bouguettaya, Ayoub, additional, Brauer, Markus, additional, Brick, Cameron, additional, Brik, Tymofii, additional, Briker, Roman, additional, Brosch, Tobias, additional, Buchel, Ondrej, additional, Buonauro, Daniel, additional, Butalia, Radhika, additional, Carvacho, Héctor, additional, Chamberlain, Sarah A. E., additional, Chan, Hang-Yee, additional, Chow, Dawn, additional, Chung, Dongil, additional, Cian, Luca, additional, Cohen-Eick, Noa, additional, Contreras-Huerta, Luis Sebastian, additional, Contu, Davide, additional, Cristea, Vladimir, additional, Cutler, Jo, additional, D'Ottone, Silvana, additional, De Keersmaecker, Jonas, additional, Delcourt, Sarah, additional, Delouvée, Sylvain, additional, Diel, Kathi, additional, Douglas, Benjamin D., additional, Drupp, Moritz A., additional, Dubey, Shreya, additional, Ekmanis, Jānis, additional, Elbaek, Christian T., additional, Elsherif, Mahmoud, additional, Engelhard, Iris M., additional, Escher, Yannik A., additional, Etienne, Tom W., additional, Farage, Laura, additional, Farias, Ana Rita, additional, Feuerriegel, Stefan, additional, Findor, Andrej, additional, Freira, Lucia, additional, Friese, Malte, additional, Gains, Neil Philip, additional, Gallyamova, Albina, additional, Geiger, Sandra J., additional, Genschow, Oliver, additional, Gjoneska, Biljana, additional, Gkinopoulos, Theofilos, additional, Goldberg, Beth, additional, Goldenberg, Amit, additional, Gradidge, Sarah, additional, Grassini, Simone, additional, Gray, Kurt, additional, Grelle, Sonja, additional, Griffin, Siobhán M., additional, Grigoryan, Lusine, additional, Grigoryan, Ani, additional, Grigoryev, Dmitry, additional, Gruber, June, additional, Guilaran, Johnrev, additional, Hadar, Britt, additional, Hahnel, Ulf J.J., additional, Halperin, Eran, additional, Harvey, Annelie J., additional, Haugestad, Christian A. P., additional, Herman, Aleksandra M., additional, Hershfield, Hal E., additional, Himichi, Toshiyuki, additional, Hine, Donald W., additional, Hofmann, Wilhelm, additional, Howe, Lauren, additional, Huaman-Chulluncuy, Enma T., additional, Huang, Guanxiong, additional, Ishii, Tatsunori, additional, Ito, Ayahito, additional, Jia, Fanli, additional, Jost, John T., additional, Jovanović, Veljko, additional, Jurgiel, Dominika, additional, Kácha, Ondřej, additional, Kankaanpää, Reeta, additional, Kantorowicz, Jaroslaw, additional, Kantorowicz-Reznichenko, Elena, additional, Kaplan Mintz, Keren, additional, Kaya, Ilker, additional, Kaya, Ozgur, additional, Khachatryan, Narine, additional, Klas, Anna, additional, Klein, Colin, additional, Klöckner, Christian A., additional, Koppel, Lina, additional, Kosachenko, Alexandra I., additional, Kothe, Emily J., additional, Krebs, Ruth, additional, Krosch, Amy R., additional, Krouwel, Andre P.M., additional, Kyrychenko, Yara, additional, Lagomarsino, Maria, additional, Lamm, Claus, additional, Lange, Florian, additional, Lee Cunningham, Julia, additional, Lees, Jeffrey, additional, Leung, Tak Yan, additional, Levy, Neil, additional, Lockwood, Patricia L., additional, Longoni, Chiara, additional, López Ortega, Alberto, additional, Loschelder, David D., additional, Lu, Jackson G., additional, Luo, Yu, additional, Luomba, Joseph, additional, Lutz, Annika E., additional, Majer, Johann M., additional, Markowitz, Ezra, additional, Marsh, Abigail A., additional, Mascarenhas, Karen Louise, additional, Mbilingi, Bwambale, additional, Mbungu, Winfred, additional, McHugh, Cillian, additional, Meijers, Marijn H.C., additional, Mercier, Hugo, additional, Mhagama, Fenant Laurent, additional, Michalakis, Katerina, additional, Mikus, Nace, additional, Milliron, Sarah, additional, Mitkidis, Panagiotis, additional, Monge-Rodríguez, Fredy S., additional, Mora, Youri L., additional, Moreau, David, additional, Motoki, Kosuke, additional, Moyano, Manuel, additional, Mus, Mathilde, additional, Navajas, Joaquin, additional, Nguyen, Tam Luong, additional, Nguyen, Dung Minh, additional, Nguyen, Trieu, additional, Niemi, Laura, additional, Nijssen, Sari R. R., additional, Nilsonne, Gustav, additional, Nitschke, Jonas P., additional, Nockur, Laila, additional, Okura, Ritah, additional, Öner, Sezin, additional, Özdoğru, Asil Ali, additional, Palumbo, Helena, additional, Panagopoulos, Costas, additional, Panasiti, Maria Serena, additional, Pärnamets, Philip, additional, Paruzel-Czachura, Mariola, additional, Pavlov, Yuri G., additional, Payán-Gómez, César, additional, Pearson, Adam R., additional, Pereira da Costa, Leonor, additional, Petrowsky, Hannes M., additional, Pfattheicher, Stefan, additional, Pham, Nhat Tan, additional, Ponizovskiy, Vladimir, additional, Pretus, Clara, additional, Rêgo, Gabriel G., additional, Reimann, Ritsaart, additional, Rhoads, Shawn A., additional, Riano-Moreno, Julian, additional, Richter, Isabell, additional, Röer, Jan Philipp, additional, Rosa-Sullivan, Jahred, additional, Ross, Robert M., additional, Sabherwal, Anandita, additional, Saito, Toshiki, additional, Sarrasin, Oriane, additional, Say, Nicolas, additional, Schmid, Katharina, additional, Schmitt, Michael T., additional, Schoenegger, Philipp, additional, Scholz, Christin, additional, Schug, Mariah G., additional, Schulreich, Stefan, additional, Shreedhar, Ganga, additional, Shuman, Eric, additional, Sivan, Smadar, additional, Sjåstad, Hallgeir, additional, Soliman, Meikel, additional, Soud, Katia, additional, Spampatti, Tobia, additional, Sparkman, Gregg, additional, Spasovski, Ognen, additional, Stanley, Samantha K., additional, Stern, Jessica A., additional, Strahm, Noel, additional, Suko, Yasushi, additional, Sul, Sunhae, additional, Syropoulos, Stylianos, additional, Taylor, Neil C., additional, Tedaldi, Elisa, additional, Tinghög, Gustav, additional, Huynh, Luu Duc Toan, additional, Travaglino, Giovanni Antonio, additional, Tsakiris, Manos, additional, Tüter, İlayda, additional, Tyrala, Michael, additional, Uluğ, Özden Melis, additional, Urbanek, Arkadiusz, additional, Valko, Danila, additional, van der Linden, Sander, additional, van Schie, Kevin, additional, van Stekelenburg, Aart, additional, Vanags, Edmunds, additional, Västfjäll, Daniel, additional, Vesely, Stepan, additional, Vintr, Jáchym, additional, Vranka, Marek, additional, Wanguche, Patrick Otuo, additional, Willer, Robb, additional, Wojcik, Adrian Dominik, additional, Xu, Rachel, additional, Yadav, Anjali, additional, Zawisza, Magdalena, additional, Zhao, Xian, additional, Zhao, Jiaying, additional, Żuk, Dawid, additional, and Van Bavel, Jay J., additional

Published
2024
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14. From field-induced to zero-field SMMs associated with open/closed structures of bis(ZnDy) tetranuclear complexes: a combined magnetic, theoretical and optical study

Author

Zabala-Lekuona, Andoni, primary, Lopez de Pariza, Xabier, additional, Díaz-Ortega, Ismael Francisco, additional, Cepeda, Javier, additional, Nojiri, Hiroyuki, additional, Gritsan, Nina P., additional, Dmitriev, A. A., additional, López-Ortega, Alberto, additional, Rodríguez Diéguez, Antonio, additional, Seco, José Manuel, additional, and Colacio, Enrique, additional

Published
2024
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15. Do political duos diminish discriminatory voter preferences? Evidence from a combined conjoint experiment.

Author

López Ortega, Alberto

Subjects
*POLITICAL parties, *VOTERS, *POLITICAL elites, *MINORITIES, *VOTING
Abstract

In Europe, more and more parties and governments are led by a pair of leaders. What consequences does the presence of duos have on voter preferences? I argue that voters have less discriminatory preferences against untraditional candidates when they choose two leaders instead of only one. However, discriminatory preferences do not entirely vanish; rather, traditionally excluded candidates are often relegated to secondary positions, and there exists a certain threshold of tolerated ticket diversity. Through a novel combined conjoint experiment, I find relative support for this conjecture, especially in the case of ethnic minority candidates. In view of the increasing number of new types of leadership, the results of this study have important implications for the study of political behaviour and elite diversity. [ABSTRACT FROM AUTHOR]

Published
2024
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20. Elucidating individual magnetic contributions in bi-magnetic Fe3O4/Mn3O4 core/shell nanoparticles by polarized powder neutron diffraction

Author

Russian Foundation for Basic Research, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, European Commission, Universidad Pública de Navarra, Golosovsky, Igor V., Kibalin. I. A., Gukasov, A., Roca, Alejandro G., López-Ortega, Alberto, Estrader, Marta, Vasilakaki, Marianna, Trohidou, Kalliopi N., Hansen, T. C., Puente-Orench, Inés, Lelièvre-Berna, E., Nogués, Josep, Russian Foundation for Basic Research, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, European Commission, Universidad Pública de Navarra, Golosovsky, Igor V., Kibalin. I. A., Gukasov, A., Roca, Alejandro G., López-Ortega, Alberto, Estrader, Marta, Vasilakaki, Marianna, Trohidou, Kalliopi N., Hansen, T. C., Puente-Orench, Inés, Lelièvre-Berna, E., and Nogués, Josep

Abstract

Heterogeneous bi-magnetic nanostructured systems have had a sustained interest during the last decades owing to their unique magnetic properties and the wide range of derived potential applications. However, elucidating the details of their magnetic properties can be rather complex. Here, a comprehensive study of Fe3 O4 /Mn3 O4 core/shell nanoparticles using polarized neutron powder diffraction, which allows disentangling the magnetic contributions of each of the components, is presented. The results show that while at low fields the Fe3 O4 and Mn3 O4 magnetic moments averaged over the unit cell are antiferromagnetically coupled, at high fields, they orient parallel to each other. This magnetic reorientation of the Mn3 O4 shell moments is associated with a gradual evolution with the applied field of the local magnetic susceptibility from anisotropic to isotropic. Additionally, the magnetic coherence length of the Fe3 O4 cores shows some unusual field dependence due to the competition between the antiferromagnetic interface interaction and the Zeeman energies. The results demonstrate the great potential of the quantitative analysis of polarized neutron powder diffraction for the study of complex multiphase magnetic materials.

Published
2023

23. Fe3O4–SiO2 Mesoporous Core/Shell Nanoparticles for Magnetic Field-Induced Ibuprofen-Controlled Release

Author

García, Lucia, primary, Garaio, Eneko, additional, López-Ortega, Alberto, additional, Galarreta-Rodriguez, Itziar, additional, Cervera-Gabalda, Laura, additional, Cruz-Quesada, Guillermo, additional, Cornejo, Alfonso, additional, Garrido, Julián J., additional, Gómez-Polo, Cristina, additional, and Pérez-Landazábal, José Ignacio, additional

Published
2022
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26. Crossover From Individual to Collective Magnetism in Dense Nanoparticle Systems: Local Anisotropy Versus Dipolar Interactions

Author

Sánchez, Elena H., primary, Vasilakaki, Marianna, additional, Lee, Su Seong, additional, Normile, Peter S., additional, Andersson, Mikael S., additional, Mathieu, Roland, additional, López‐Ortega, Alberto, additional, Pichon, Benoit P., additional, Peddis, Davide, additional, Binns, Chris, additional, Nordblad, Per, additional, Trohidou, Kalliopi, additional, Nogués, Josep, additional, and De Toro, José A., additional

Published
2022
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27. Supporting Information for Small, DOI: 10.1002/smll.202106762 Crossover From Individual to Collective Magnetism in Dense Nanoparticle Systems: Local Anisotropy Versus Dipolar Interactions

Author

Generalitat de Catalunya, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Sánchez, Elena H., Vasilakaki, Marianna, Lee, Su Seong, Normile, Peter S., Andersson, Mikael S., Mathieu, Roland, López-Ortega, Alberto, Pichon, Benoit P., Peddis, Davide, Binns, Chris, Nordblad, Per, Trohidou, Kalliopi N., Nogués, Josep, Toro, José A. de, Generalitat de Catalunya, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Sánchez, Elena H., Vasilakaki, Marianna, Lee, Su Seong, Normile, Peter S., Andersson, Mikael S., Mathieu, Roland, López-Ortega, Alberto, Pichon, Benoit P., Peddis, Davide, Binns, Chris, Nordblad, Per, Trohidou, Kalliopi N., Nogués, Josep, and Toro, José A. de

Published
2022

28. Hardening of Cobalt Ferrite Nanoparticles by Local Crystal Strain Release: Implications for Rare Earth Free Magnets

Author

Universidad Pública de Navarra, Muzzi, Beatrice, Lottini, Elisabetta, Yaacoub, Nader, Peddis, Davide, Bertoni, Giovanni, Julián Fernández, César de, Sangregorio, Claudio, López-Ortega, Alberto, AMPHIBIAN Project ID:720853, Universidad Pública de Navarra, Muzzi, Beatrice, Lottini, Elisabetta, Yaacoub, Nader, Peddis, Davide, Bertoni, Giovanni, Julián Fernández, César de, Sangregorio, Claudio, López-Ortega, Alberto, and AMPHIBIAN Project ID:720853

Abstract

[EN] In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets.

Published
2022

29. Crossover from individual to collective magnetism in dense nanoparticle systems: Local anisotropy versus dipolar interactions

Author

Ministerio de Economía y Competitividad (España), European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Swedish Research Council, Generalitat de Catalunya, Universidad Pública de Navarra, Sánchez, Elena H., Vasilakaki, Marianna, Lee, Su Seong, Normile, Peter S., Andersson, Mikael S., Mathieu, Roland, López-Ortega, Alberto, Pichon, Benoit P., Peddis, Davide, Binns, Chris, Nordblad, Per, Trohidou, Kalliopi N., Nogués, Josep, Toro, José A. de, Ministerio de Economía y Competitividad (España), European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Swedish Research Council, Generalitat de Catalunya, Universidad Pública de Navarra, Sánchez, Elena H., Vasilakaki, Marianna, Lee, Su Seong, Normile, Peter S., Andersson, Mikael S., Mathieu, Roland, López-Ortega, Alberto, Pichon, Benoit P., Peddis, Davide, Binns, Chris, Nordblad, Per, Trohidou, Kalliopi N., Nogués, Josep, and Toro, José A. de

Abstract

Dense systems of magnetic nanoparticles may exhibit dipolar collective behavior. However, two fundamental questions remain unsolved: i) whether the transition temperature may be affected by the particle anisotropy or it is essentially determined by the intensity of the interparticle dipolar interactions, and ii) what is the minimum ratio of dipole–dipole interaction (Edd) to nanoparticle anisotropy (KefV, anisotropy⋅volume) energies necessary to crossover from individual to collective behavior. A series of particle assemblies with similarly intense dipolar interactions but widely varying anisotropy is studied. The Kef is tuned through different degrees of cobalt-doping in maghemite nanoparticles, resulting in a variation of nearly an order of magnitude. All the bare particle compacts display collective behavior, except the one made with the highest anisotropy particles, which presents “marginal” features. Thus, a threshold of KefV/Edd ≈ 130 to suppress collective behavior is derived, in good agreement with Monte Carlo simulations. This translates into a crossover value of ≈1.7 for the easily accessible parameter TMAX(interacting)/TMAX(non-interacting) (ratio of the peak temperatures of the zero-field-cooled magnetization curves of interacting and dilute particle systems), which is successfully tested against the literature to predict the individual-like/collective behavior of any given interacting particle assembly comprising relatively uniform particles.

Published
2022

33. Precise size control of the growth of Fe3O4 nanocubes over a wide size range using a rationally designed one-pot synthesis

Author

Generalitat de Catalunya, Agencia Estatal de Investigación (España), Ministerio de Economía, Industria y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), Università di Pisa, Muro-Cruces, Javier [0000-0003-1857-1314], Roca, Alejandro G. [0000-0001-6610-9197], López-Ortega, Alberto [0000-0003-3440-4444], Fantechi, Elvira [0000-0002-9323-2198], Pineider, Francesco [0000-0003-4066-4031], Sangregorio, Claudio [0000-0002-2655-3901], Nogués, Josep [0000-0003-4616-1371], Muro-Cruces, Javier, Roca, Alejandro G., López-Ortega, Alberto, Fantechi, Elvira, Pozo-Bueno, Daniel del, Estradé, Sònia, Peiró, Francesca, Sepúlveda, Borja, Pineider, Francesco, Sangregorio, Claudio, Nogués, Josep, Generalitat de Catalunya, Agencia Estatal de Investigación (España), Ministerio de Economía, Industria y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), Università di Pisa, Muro-Cruces, Javier [0000-0003-1857-1314], Roca, Alejandro G. [0000-0001-6610-9197], López-Ortega, Alberto [0000-0003-3440-4444], Fantechi, Elvira [0000-0002-9323-2198], Pineider, Francesco [0000-0003-4066-4031], Sangregorio, Claudio [0000-0002-2655-3901], Nogués, Josep [0000-0003-4616-1371], Muro-Cruces, Javier, Roca, Alejandro G., López-Ortega, Alberto, Fantechi, Elvira, Pozo-Bueno, Daniel del, Estradé, Sònia, Peiró, Francesca, Sepúlveda, Borja, Pineider, Francesco, Sangregorio, Claudio, and Nogués, Josep

Abstract

The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe3O4 nanocubes with edge length in the 9–80 nm range, with excellent cubic morphology and high crystallinity by only minor adjustments in the synthesis parameters. The accurate size control provides evidence that even 1–2 nm size variations can be critical in determining the functional properties, for example, for improved nuclear magnetic resonance T2 contrast or enhanced magnetic hyperthermia. The rationale behind the changes introduced in the synthesis procedure (e.g., the use of three solvents or adding Na-oleate) is carefully discussed. The versatility of this synthesis route is demonstrated by expanding its capability to grow other spinel oxides such as Co-ferrites, Mn-ferrites, and Mn3O4 of different sizes. The simplicity and adaptability of this synthesis scheme may ease the development of complex oxide nanocubes for a wide variety of applications.

Published
2019

34. Ligand-induced reduction concerted with coating by atomic layer deposition on the example of TiO2-coated magnetite nanoparticles† †Electronic supplementary information (ESI) available: Magnetization vs. temperature graphics of comparison samples. List of possible reaction schemes and DFT calculated reaction energies for reducing Fe2O3 to Fe3O4 by using different ALD precursors. XRD patterns of TiO2-coated (TDMATi–FeOx) and uncoated FeOx nanoparticles before and after the annealing process. See DOI: 10.1039/c8sc04474k

Author

García-García, Sarai, López-Ortega, Alberto, Zheng, Yongping, Nie, Yifan, Cho, Kyeongjae, Chuvilin, Andrey, and Knez, Mato

Subjects
Chemistry
Abstract

An appropriate atomic layer deposition precursor, as a function of the ligand of the metal source, can unveil a novel approach to concertedly coat and reduce γ-Fe2O3 nanoparticles to form Fe3O4/TiO2 core/shell nanoparticles., Atomic layer deposition is a chemical deposition technology that provides ultimate control over the conformality of films and their thickness, even down to Ångström-scale precision. Based on the marked superficial character and gas phase process of the technique, metal sources and their ligands shall ideally be highly volatile. However, in numerous cases those ligands corrode the substrate or compete for adsorption sites, well-known as side reactions of these processes. Therefore, the ability to control such side reactions might be of great interest, since it could achieve synchronous coating and alteration of a substrate in one process, saving time and energy otherwise needed for a post-treatment of the sample. Consequently, advances in this way must require understanding and control of the chemical processes that occur during the coating. In this work, we show how choosing an appropriate ligand of the metal source can unveil a novel approach to concertedly coat and reduce γ-Fe2O3 nanoparticles to form a final product composed of Fe3O4/TiO2 core/shell nanoparticles. To this aim, we envisage that appropriate design of precursors and selection of substrates will pave the way for numerous new compositions, while the ALD process itself allows for easy upscaling to large amounts of coated and reduced particles for industrial use.

Published
2018

38. Direct Evidence of a Graded Magnetic Interface in Bimagnetic Core/Shell Nanoparticles Using Electron Magnetic Circular Dichroism (EMCD)

Author

Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, Universidad Complutense de Madrid, Pozo-Bueno, Daniel del, Varela, María, Estrader, Marta, López-Ortega, Alberto, Roca, Alejandro G., Nogués, Josep, Peiró, Francesca, Estradé, Sònia, Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, Universidad Complutense de Madrid, Pozo-Bueno, Daniel del, Varela, María, Estrader, Marta, López-Ortega, Alberto, Roca, Alejandro G., Nogués, Josep, Peiró, Francesca, and Estradé, Sònia

Abstract

Interfaces play a crucial role in composite magnetic materials and particularly in bimagnetic core/shell nanoparticles. However, resolving the microscopic magnetic structure of these nanoparticles is rather complex. Here, we investigate the local magnetization of antiferromagnetic/ferrimagnetic FeO/Fe3O4 core/shell nanocubes by electron magnetic circular dichroism (EMCD). The electron energy-loss spectroscopy (EELS) compositional analysis of the samples shows the presence of an oxidation gradient at the interface between the FeO core and the Fe3O4 shell. The EMCD measurements show that the nanoparticles are composed of four different zones with distinct magnetic moment in a concentric, onion-type, structure. These magnetic areas correlate spatially with the oxidation and composition gradient with the magnetic moment being largest at the surface and decreasing toward the core. The results show that the combination of EELS compositional mapping and EMCD can provide very valuable information on the inner magnetic structure and its correlation to the microstructure of magnetic nanoparticles.

Published
2021

39. A caging strategy for tuning the magneto-optical properties of cobalt ferrite using a single plasmonic nanoparticle

Author

Testa-Anta, Martín, Sousa-Castillo, Ana, López-Ortega, Alberto, Correa-Duarte, Miguel A., García-Martín, Antonio, Vavassori, Paolo, Salgueiriño-Maceira, Verónica, Testa-Anta, Martín, Sousa-Castillo, Ana, López-Ortega, Alberto, Correa-Duarte, Miguel A., García-Martín, Antonio, Vavassori, Paolo, and Salgueiriño-Maceira, Verónica

Abstract

The composite nanostructures with magnetic and plasmonic functionalities herein described were produced according to a unique synthetic strategy by which numerous cobalt ferrite nanoparticles accompanied by an individual gold nanoparticle were confined in silica capsules. This assembly offers a distinctive system on which the influence of the surface plasmon of a single 20 or 60 nm-in-diameter gold nanoparticle is proved to increase the visible range magneto-optical activity of the cobalt ferrite magnetic material. Consequently, it provides a key strategy for the production of nanostructures including different materials as building blocks, taking advantage of the confined coupling for the development of materials with enhanced magneto-optical capabilities.

Published
2021

40. Probing the meta-stability of oxide core/shell nanoparticle systems at atomic resolution

Author

European Research Council, Japan Society for the Promotion of Science, Ministerio de Economía y Competitividad (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), European Commission, Department of Energy (US), Knut and Alice Wallenberg Foundation, Generalitat de Catalunya, Oak Ridge National Laboratory (US), National University of Singapore, Roldán, Manuel A., Mayence, Arnaud, López-Ortega, Alberto, Ishikawa, Ryo, Salafranca, Juan, Estrader, Marta, Salazar-Álvarez, G., Baró, María Dolors, Nogués, Josep, Pennycook, Stephen J., Varela, María, European Research Council, Japan Society for the Promotion of Science, Ministerio de Economía y Competitividad (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), European Commission, Department of Energy (US), Knut and Alice Wallenberg Foundation, Generalitat de Catalunya, Oak Ridge National Laboratory (US), National University of Singapore, Roldán, Manuel A., Mayence, Arnaud, López-Ortega, Alberto, Ishikawa, Ryo, Salafranca, Juan, Estrader, Marta, Salazar-Álvarez, G., Baró, María Dolors, Nogués, Josep, Pennycook, Stephen J., and Varela, María

Abstract

Hybrid nanoparticles allow exploiting the interplay of confinement, proximity between different materials and interfacial effects. However, to harness their properties an in-depth understanding of their (meta)stability and interfacial characteristics is crucial. This is especially the case of nanosystems based on functional oxides working under reducing conditions, which may severely impact their properties. In this work, the in-situ electron-induced selective reduction of Mn3O4 to MnO is studied in magnetic Fe3O4/Mn3O4 and Mn3O4/Fe3O4 core/shell nanoparticles by means of high-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Such in-situ transformation allows mimicking the actual processes in operando environments. A multi-stage image analysis using geometric phase analysis combined with particle image velocity enables direct monitoring of the relationship between structure, chemical composition and strain relaxation during the Mn3O4 reduction. In the case of Fe3O4/Mn3O4 core/shell the transformation occurs smoothly without the formation of defects. However, for the inverse Mn3O4/Fe3O4 core/shell configuration the electron beam-induced transformation occurs in different stages that include redox reactions and void formation followed by strain field relaxation via formation of defects. This study highlights the relevance of understanding the local dynamics responsible for changes in the particle composition in order to control stability and, ultimately, macroscopic functionality.

Published
2021

41. Fe3O4–SiO2Mesoporous Core/Shell Nanoparticles for Magnetic Field-Induced Ibuprofen-Controlled Release

Author

García, Lucia, Garaio, Eneko, López-Ortega, Alberto, Galarreta-Rodriguez, Itziar, Cervera-Gabalda, Laura, Cruz-Quesada, Guillermo, Cornejo, Alfonso, Garrido, Julián J., Gómez-Polo, Cristina, and Pérez-Landazábal, José Ignacio

Abstract

Hybrid magnetic nanoparticles made up of an iron oxide, Fe3O4, core and a mesoporous SiO2shell with high magnetization and a large surface area were proposed as an efficient drug delivery platform. The core/shell structure was synthesized by two seed-mediated growth steps combining solvothermal and sol–gel approaches and using organic molecules as a porous scaffolding template. The system presents a mean particle diameter of 30(5) nm (9 nm magnetic core diameter and 10 nm silica shell thickness) with superparamagnetic behavior, saturation magnetization of 32 emu/g, and a significant AC magnetic-field-induced heating response (SAR = 63 W/gFe3O4, measured at an amplitude of 400 Oe and a frequency of 307 kHz). Using ibuprofen as a model drug, the specific surface area (231 m2/g) of the porous structure exhibits a high molecule loading capacity (10 wt %), and controlled drug release efficiency (67%) can be achieved using the external AC magnetic field for short time periods (5 min), showing faster and higher drug desorption compared to that of similar stimulus-responsive iron oxide-based nanocarriers. In addition, it is demonstrated that the magnetic field-induced drug release shows higher efficiency compared to that of the sustained release at fixed temperatures (47 and 53% for 37 and 42 °C, respectively), considering that the maximum temperature reached during the exposure to the magnetic field is well below (31 °C). Therefore, it can be hypothesized that short periods of exposure to the oscillating field induce much greater heating within the nanoparticles than in the external solution.

Published
2023
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42. Atomic-scale determination of cation inversion in spinel-based oxide nanoparticles

Author

Ministerio de Economía y Competitividad (España), European Commission, Generalitat de Catalunya, Torruella, Pau [0000-0002-6864-4000], Roca, Alejandro G. [0000-0001-6610-9197], López-Ortega, Alberto [0000-0003-3440-4444], Blanco-Portals, Javier [0000-0002-7037-269X], López-Conesa, Lluís [0000-0003-1456-079X], Torruella, Pau, Ruiz-Caridad, Alicia, Walls, Michael, Roca, Alejandro G., López-Ortega, Alberto, Blanco-Portals, Javier, López-Conesa, Lluís, Nogués, Josep, Peiró, Francesca, Estradé, Sònia, Ministerio de Economía y Competitividad (España), European Commission, Generalitat de Catalunya, Torruella, Pau [0000-0002-6864-4000], Roca, Alejandro G. [0000-0001-6610-9197], López-Ortega, Alberto [0000-0003-3440-4444], Blanco-Portals, Javier [0000-0002-7037-269X], López-Conesa, Lluís [0000-0003-1456-079X], Torruella, Pau, Ruiz-Caridad, Alicia, Walls, Michael, Roca, Alejandro G., López-Ortega, Alberto, Blanco-Portals, Javier, López-Conesa, Lluís, Nogués, Josep, Peiró, Francesca, and Estradé, Sònia

Abstract

The atomic structure of nanoparticles can be easily determined by transmission electron microscopy. However, obtaining atomic-resolution chemical information about the individual atomic columns is a rather challenging endeavor. Here, crystalline monodispersed spinel Fe3O4/Mn3O4 core–shell nanoparticles have been thoroughly characterized in a high-resolution scanning transmission electron microscope. Electron energy-loss spectroscopy (EELS) measurements performed with atomic resolution allow the direct mapping of the Mn2+/Mn3+ ions in the shell and the Fe2+/Fe3+ in the core structure. This enables a precise understanding of the core–shell interface and of the cation distribution in the crystalline lattice of the nanoparticles. Considering how the different oxidation states of transition metals are reflected in EELS, two methods of performing a local evaluation of the cation inversion in spinel lattices are introduced. Both methods allow the determination of the inversion parameter in the iron oxide core and manganese oxide shell, as well as detecting spatial variations in this parameter, with atomic resolution. X-ray absorption measurements on the whole sample confirm the presence of cation inversion. These results present a significant advance toward a better correlation of the structural and functional properties of nanostructured spinel oxides.

Published
2018

43. Poster: Spin-Related Phenomena

Author

Djieutedjeu, Honore, primary, Ranmohotti, Kulugammana G. S., additional, Takas, Nathan J., additional, Makongo, Julien P. A., additional, Zhou, Xiaoyuan, additional, Uher, Ctirad, additional, Haldolaarachchige, N., additional, Young, D. P., additional, Poudeu, Pierre F. P., additional, Kirilmaz, O., additional, Paul, M., additional, Müller, A., additional, Kufer, D., additional, Sing, M., additional, Claessen, R., additional, Brück, S., additional, Praetorius, C., additional, Fauth, K., additional, Kamp, M., additional, Audehm, P., additional, Goering, E., additional, Verbeeck, J., additional, Tian, H., additional, Van Tendeloo, G., additional, Ingle, N. J. C., additional, Przybylski, M., additional, Gorgoi, M., additional, Iván, Bernal, additional, Silvia, Gallego, additional, Kashid, Vikas, additional, Shah, Vaishali, additional, Salunke, H. G., additional, Mokrousov, Y., additional, Blügel, S., additional, Fuchs, Dirk, additional, Merz, Michael, additional, Dieterle, Levin, additional, Uebe, Stefan, additional, Nagel, Peter, additional, Schuppler, Stefan, additional, Gerthsen, Dagmar, additional, von Löhneysen, Hilbert, additional, Togawa, Yoshihiko, additional, Koyama, Tsukasa, additional, Mori, Shigeo, additional, Kousaka, Yusuke, additional, Akimitsu, Jun, additional, Nishihara, Sadafumi, additional, Inoue, Katsuya, additional, Ovchinnikov, Alexander, additional, Kishine, Jun-Ichiro, additional, Mahendiran, Ramanathan, additional, Xiao, Y., additional, Su, Y., additional, Nandi, S., additional, Price, S., additional, Brückel, Th., additional, Zimmermann, B., additional, Mavropoulos, P., additional, Heers, S., additional, Long, N. H., additional, Sasioglu, Ersoy, additional, Friedrich, Christoph, additional, Blügel, Stefan, additional, Moshnyaga, V., additional, Binek, Christian, additional, He, Xi, additional, Wang, Yi, additional, Wu, N., additional, Wysocki, Aleksander L., additional, Komesu, Takashi, additional, Lanke, Uday, additional, Caruso, Anthony N., additional, Vescovo, Elio, additional, Belashchenko, Kirill D., additional, Dowben, Peter A., additional, Sando, Daniel, additional, Agbelele, Arsène, additional, Daumont, Christophe, additional, Juraszek, Jean, additional, Cazayous, Maximilien, additional, Infante, Ingrid, additional, Ren, Wei, additional, Lisenkov, Sergey, additional, Carretero, Cécile, additional, Bellaiche, Laurent, additional, Dkhil, Brahim, additional, Barthélémy, Agnès, additional, Bibes, Manuel, additional, Zhou, Xianzhong, additional, Mennig, Julius, additional, Matthes, Frank, additional, Bürgler, Daniel E., additional, Schneider, Claus M., additional, Herpers, Anja, additional, Park, Chanwoo, additional, Egoavil, Ricardo, additional, Verbeeck, Jo, additional, Dittmann, Regina, additional, Kurbakov, A. I., additional, Abdel-Latif, I. A., additional, Trunov, V. A., additional, Habermeier, H. U., additional, Al-Hajry, A., additional, Malyshev, A. L., additional, Ulyanov, V. A., additional, Kishine, J., additional, Ovchinnikov, A. S., additional, Proskurin, I. V., additional, Saltzmann, T., additional, Rieß, S., additional, Kampmeier, J., additional, Mussler, G., additional, Stoica, T., additional, Kardynal, B., additional, Simon, U., additional, Hardtdegen, H., additional, Felser, C., additional, Müchler, L., additional, Chadov, S., additional, Yan, B., additional, Kübler, J., additional, Zhang, HJ, additional, Zhang, SC, additional, Pauly, Christian, additional, Bihlmayer, Gustav, additional, Liebmann, Marcus, additional, Grob, Martin, additional, Georgi, Alexander, additional, Subramaniam, Dinesh, additional, Scholz, Markus, additional, Sánchez-Barriga, Jaime, additional, Varykhalov, Andrei, additional, Rader, Oliver, additional, Morgenstern, Markus, additional, Aguilera, Irene, additional, Rushchanskii, Konstantin Z., additional, Garcia-Sanchez, Felipe, additional, Hertel, Riccardo, additional, Ležaić, Marjana, additional, Goian, Veronica, additional, Kamba, Stanislav, additional, Kadlec, Christelle, additional, Kužel, Petr, additional, Pisarev, Roman V., additional, Foschini, C. R., additional, Moura, F., additional, Ramirez, M. A., additional, Varela, J. A., additional, Longo, E., additional, Simões, A. Z., additional, Iusan, Diana, additional, Yamauchi, Kunihiko, additional, Delaney, Kris, additional, Picozzi, Silvia, additional, Yu, Jian, additional, Zhang, Linlin, additional, Hou, Xianbo, additional, Yedra, Lluís., additional, Estradé, Sònia, additional, Pellicer, Eva., additional, Cabo, Moisés, additional, López-Ortega, Alberto, additional, Estrader, Marta, additional, Nogués, Josep, additional, Baró, Dolors, additional, Saghi, Zineb, additional, Midgley, Paul A., additional, Peiró, Francesca, additional, Schena, Timo, additional, and Zimmermann, Bernd, additional

Published
2013
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46. Study of magnetic iron oxide core/shell nanocubes using electron magnetic circular dichroism

Author

Pozo-Bueno, Daniel del, Estradé, Sònia, Varela, María, Estrader, Marta, López-Ortega, Alberto, Nogués, Josep, and Peiró, Francesca

Subjects
EMCD, Magnetite, Nanocubes, Iron oxide, Magnetism, Core/shell nanoparticles
Abstract

Resumen del trabajo presentado al Microscopy at the Frontiers of Science Congress Series (MFS), celebrado en el Parque de las Ciencias de Granada (España) del 11 al 13 de septiembre de 2019.

Published
2019

47. Actitudes públicas sobre la (in)seguridad energética: evidencia de España

Author

Muradova, Lala, López Ortega, Alberto, Muradova, Lala, and López Ortega, Alberto

Abstract

This study investigates how citizens perceive energy security challenges, by analysing an original survey data fielded in a quota sample of Spanish citizens (n=339). Findings demonstrate that energy security in general and the affordability of household electricity prices in particular is of extremely high concern for the citizens. Older citizens in our sample are more worried about the equitable access to energy services than the younger population. Citizens with more education are more aware of energy security risks. Creating closer ties between the public and policy makers, by raising awareness on energy matters and fostering a public debate around the issue of energy security could decrease the mismatch between the energy needs of energy-users and the energy policies, and eventually alleviate energy troubles of the most disadvantaged., Este estudio investiga cómo perciben los ciudadanos los retos de la seguridad energética, analizando los datos originales de una encuesta realizada en una muestra de cuota de ciudadanos españoles (n=339). Los resultados demuestran que la seguridad energética en general y la asequibilidad de los precios de la electricidad en los hogares en particular son motivo de gran preocupación para los ciudadanos. Los ciudadanos mayores de nuestra muestra parecen estar más preocupados por el acceso equitativo a los servicios energéticos que la población más joven. Los ciudadanos con más educación parecen ser más conscientes de los riesgos de la seguridad energética. La creación de vínculos más estrechos entre el público y los responsables políticos, mediante la sensibilización sobre cuestiones energéticas y el fomento de un debate público en torno a la cuestión de la seguridad energética, podría reducir el desajuste entre las necesidades energéticas de los usuarios de energía y las políticas energéticas y, en última instancia, aliviar los problemas energéticos de los más desfavorecidos.

Published
2019

48. Zinc blende and wurtzite CoO polymorph nanoparticles: rational synthesis and commensurate and incommensurate magnetic order

Author

Ministerio de Economía y Competitividad (España), Generalitat de Catalunya, Agencia Estatal de Investigación (España), Russian Foundation for Basic Research, Ministerio de Ciencia, Innovación y Universidades (España), Golosovsky, Igor V., Estrader, Marta, López-Ortega, Alberto, Roca, Alejandro G., López-Conesa, Lluís, Del Corro, Elena, Estradé, Sònia, Peiró, Francesca, Puente-Orench, Inés, Nogués, Josep, Ministerio de Economía y Competitividad (España), Generalitat de Catalunya, Agencia Estatal de Investigación (España), Russian Foundation for Basic Research, Ministerio de Ciencia, Innovación y Universidades (España), Golosovsky, Igor V., Estrader, Marta, López-Ortega, Alberto, Roca, Alejandro G., López-Conesa, Lluís, Del Corro, Elena, Estradé, Sònia, Peiró, Francesca, Puente-Orench, Inés, and Nogués, Josep

Abstract

On the nanoscale, CoO can have different polymorph crystal structures, zinc blende and wurtzite, apart from rock salt, which is the stable one in bulk. However, the magnetic structures of the zinc blende and wurtzite phases remain virtually unexplored. Here we discuss some of the main parameters controlling the growth of the CoO wurtzite and zinc blende polymorphs by thermal decomposition of cobalt (II) acetylacetonate. In addition, we present a detailed neutron diffraction study of oxygen deficient CoO (CoO0.70–0.75) nanoparticles with zinc blende (∼15 nm) and wurtzite (∼30 nm) crystal structures to unravel their magnetic order and its temperature evolution. The magnetic order of the zinc blende nanoparticles is antiferromagnetic and appears at the Néel temperature TN ∼ 203 K. It corresponds to the 3rd type of magnetic ordering in a face-centered cubic lattice with magnetic moments aligned along a cube edge. The magnetic structure in the wurtzite nanoparticles turned out to be rather complex with two perpendicular components. One component is incommensurate, of the longitudinal spin wave type, with the magnetic moments confined in the ab-plane. In the perpendicular direction, this magnetic order is uncorrelated, forming quasi-two-dimensional magnetic layers. The component of the magnetic moment, aligned along the hexagonal axis, is commensurate and corresponds to the antiferromagnetic order known as the 2nd type in a wurtzite structure. The Néel temperature of wurtzite phase is estimated to be ∼109 K. The temperature dependence of the magnetic reflections confirms the reduced dimensionality of the incommensurate magnetic order. Incommensurate magnetic structures in nanoparticles are an unusual phenomenon and in the case of wurtzite CoO it is probably caused by structural defects (e.g., vacancies, strains and stacking faults).

Published
2019

49. Precise Size Control of the Growth of Fe3O4 Nanocubes over a Wide Size Range Using a Rationally Designed One-Pot Synthesis

Author

Muro-Cruces, Javier, primary, Roca, Alejandro G., additional, López-Ortega, Alberto, additional, Fantechi, Elvira, additional, del-Pozo-Bueno, Daniel, additional, Estradé, Sònia, additional, Peiró, Francesca, additional, Sepúlveda, Borja, additional, Pineider, Francesco, additional, Sangregorio, Claudio, additional, and Nogues, Josep, additional

Published
2019
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50. Role of Zn2+ Substitution on the Magnetic, Hyperthermic, and Relaxometric Properties of Cobalt Ferrite Nanoparticles

Author

Albino, Martin, primary, Fantechi, Elvira, additional, Innocenti, Claudia, additional, López-Ortega, Alberto, additional, Bonanni, Valentina, additional, Campo, Giulio, additional, Pineider, Francesco, additional, Gurioli, Massimo, additional, Arosio, Paolo, additional, Orlando, Tomas, additional, Bertoni, Giovanni, additional, de Julián Fernández, Cesar, additional, Lascialfari, Alessandro, additional, and Sangregorio, Claudio, additional

Published
2019
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