BUSCADOR RECOLECTA

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., The authors acknowledge the financial support from the Spanish Minister of Science and Innovation (MICINN) through the projects PID2019-106165GB-C21, PID2019-106165GB-C22, and PID2019-106229RB-I00. They also acknowledge funding from Generalitat de Catalunya through the 2017-SGR-292 and 2017-SGR-776 projects. In addition, research at UCM was supported by MINECO/FEDER MAT2015-66888-C3-3-R and RTI2018-097895-B-C43 grants. ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, Grant SEV-2017-0706). M.E. thanks the Spanish MICINN and AEI/FSE for Ramón y Cajal contract (RYC2018-024396-I). A.L.O. acknowledges support from the Universidad Pública de Navarra (Grant PJUPNA2020). STEM-EELS observations carried out at the Centro Nacional de Microscopía Electrónica at Universidad Complutense de Madrid, Spain (ICTS ELECMI).

The resistance of an ordered 3D-Bi2Te3 nanowire nanonetwork was studied at low temperatures. Below 50 K the increase in resistance
was found to be compatible with the Anderson model for localization,
considering that conduction takes place in individual parallel channels
across the whole sample. Angle-dependent magnetoresistance measurements showed a distinctive weak antilocalization characteristic with a
double feature that we could associate with transport along two
perpendicular directions, dictated by the spatial arrangement of the
nanowires. The coherence length obtained from the Hikami−Larkin−
Nagaoka model was about 700 nm across transversal nanowires, which
corresponded to approximately 10 nanowire junctions. Along the individual
nanowires, the coherence length was greatly reduced to about 100 nm. The
observed localization effects could be the reason for the enhancement of the
Seebeck coefficient observed in the 3D-Bi2Te3 nanowire nanonetwork
compared to individual nanowires.

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry to study oxygen mass transport and the defect compensation mechanism of Mn-deficient La0.8Sr0.2Mn (y) O-3 +/-delta epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modeling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La-x(Mn) antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties.

Finding simple, easily controlled, and flexible synthetic routes for the preparation of ternary and hybrid nanostructured semiconductors is always highly desirable, especially to fulfill the requirements for mass production to enable application to many fields such as optoelectronics, thermoelectricity, and catalysis. Moreover, understanding the underlying reaction mechanisms is equally important, offering a starting point for its extrapolation from one system to another. In this work, we developed a new and more straightforward colloidal synthetic way to form hybrid Au-A g 2 X (X = S, Se) nanoparticles under mild conditions through the reaction of Au and Ag2X nanostructured precursors in solution. At the solid-solid interface between metallic domains and the binary chalcogenide domains, a small fraction of a ternary AuAg3X2 phase was observed to have grown as a consequence of a solid-state electrochemical reaction, as confirmed by computational studies. Thus, the formation of stable ternary phases drives the selective hetero-attachment of Au and Ag2X nanoparticles in solution, consolidates the interface between their domains, and stabilizes the whole hybrid Au-Ag2X systems., A.F. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) through no. PID2019-106165GB-C22 and from the regional Generalitat de Catalunya authority (no. 2017 SGR 15). A.F. is a Serra Hunter ́ fellow. L.Y. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) through the Juan de la Cierva Incorporación grant no. IJC2018-037698-I. J.B., S.E., and F.P. from the Consolidated Research Group of the “Generalitat de Catalunya” MIND (Micro-nanotechnology and Nanoscopies for Electronic and Photonic Devices) (2017 SGR 776) acknowledge the financial support from the Spanish Ministery of Science and Innovation (MICINN) through project no. PID2019-106165GB-C21, the Spanish Research Network no. RED2018-102609-T, and the FI-AGAUR Research Fellowship Program, Generalitat de Catalunya (FI grant no. 2018FI_B_00360). This work was also co-financed by the 2014−2020 ERDF Operational Programme and the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia, project reference
no. FEDER-UCA18-107139., 12 páginas

Understanding the interactions among magnetic nanostructures is one of the key factors to predict and control the advanced functionalities of 3D integrated magnetic nanostructures. In this work, the focus is on different interconnected Ni nanowires forming an intricate, but controlled, and ordered magnetic system: Ni 3D Nanowire Networks (3DNNs). These self-ordered systems present striking anisotropic magnetic responses, depending on the interconnections’ position between nanowires. To understand their collective magnetic behavior, the magnetization reversal processes are studied within different Ni 3D Nanowire Networks compared to the 1D nanowire 1DNW array counterparts. The systems are characterized at different angles using first magnetization curves, hysteresis loops, and First Order Reversal Curves techniques, which provided information about the key features that enable macroscopic tuning of the magnetic properties of the 3D nanostructures. In addition, micromagnetic simulations endorse the experiments, providing accurate modeling of their magnetic behavior. The results reveal a plethora of magnetic interactions, neither evident nor intuitive, which are the main role players controlling the collective response of the system. The results pave the way for the design and realization of 3D novel metamaterials and devices based on the nucleation and propagation of ferromagnetic domain walls both in 3D self-ordered systems and future nano-lithographed devices., M.M.G. and O.C.C. acknowledge the financial support from the project PID2020-118430GB-100 (MICINN). J.B.P., and F.P. acknowledge the financial support from PID2019-106165GB-C21 (MICINN) and M. López-Haro and J.J. Calvino from the University of Cádiz for the acquisition of the electron tomography series. The authors also acknowledge the service from the X-SEM Laboratory at IMM, and funding from MINECO under project CSIC13-4E-1794 with support from the EU (FEDER, FSE). The authors acknowledge the support for simulation hardware from J.L. Mesa at INTA. D.N. acknowledges the financial support from the project PID2019-108075RB-C31 and the grant RYC-2017-22820 funded by MICINN/10.13039/501100011033 and by “ESF Investing in your future”., Peerreview

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., The authors acknowledge the financial support from the Spanish Minister of Science and Innovation (MICINN) through the projects PID2019-106165GB-C21, PID2019-106165GB-C22, and PID2019-106229RB-I00. They also acknowledge funding from Generalitat de Catalunya through the 2017-SGR-292 and 2017-SGR-776 projects. In addition, research at UCM was supported by MINECO/FEDER MAT2015-66888-C3-3-R and RTI2018-097895-B-C43 grants. ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, Grant SEV-2017-0706). M.E. thanks the Spanish MICINN and AEI/FSE for Ramón y Cajal contract (RYC2018-024396-I). A.L.O. acknowledges support from the Universidad Pública de Navarra (Grant PJUPNA2020). STEM-EELS observations carried out at the Centro Nacional de Microscopía Electrónica at Universidad Complutense de Madrid, Spain (ICTS ELECMI).

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry to study oxygen mass transport and the defect compensation mechanism of Mn-deficient LaSrMn O epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modeling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La Mn × antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties., This research was supported by the funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 101017709 (EPISTORE) and the 'Generalitat de Catalunya' (2017 SGR 1421, NANOEN). LY acknowledges support from the MINECO (Spain) through the IJC2018-037698-I grant. MICIIN projects PID2019-106165GB-C21 and RED2018-102609-T are also acknowledged. PN acknowledges the support from the AGAUR through the 2021 FI_B 00157 Grant. RADS acknowledges funding from German Research Foundation (DFG) from project DE 2854/12-1 and from the collaborative research center SFB917 'Nanoswitches'. J S acknowledges the financial support of the Spanish Ministry of Economy, Industry and Competitiveness (Project: PID2019-108573GB-C21).

The resistance of an ordered 3D-Bi2Te3 nanowire nanonetwork was studied at low temperatures. Below 50 K the increase in resistance was found to be compatible with the Anderson model for localization, considering that conduction takes place in individual parallel channels across the whole sample. Angle-dependent magnetoresistance measurements showed a distinctive weak antilocalization characteristic with a double feature that we could associate with transport along two perpendicular directions, dictated by the spatial arrangement of the nanowires. The coherence length obtained from the Hikami-Larkin-Nagaoka model was about 700 nm across transversal nanowires, which corresponded to approximately 10 nanowire junctions. Along the individual nanowires, the coherence length was greatly reduced to about 100 nm. The observed localization effects could be the reason for the enhancement of the Seebeck coefficient observed in the 3D-Bi2Te3 nanowire nanonetwork compared to individual nanowires., The authors would like to acknowledge the financial supportfrom the projects ERC Adv. POWERbyU 101052603,PID2020-118430GB-100, and PID2019-106165GB-C21 (MI-CINN) and project 2D-MESES from CSIC. This work wasalso cofinanced by the 2014−2020 ERDF OperationalProgramme and the Department of Economy, Knowledge,Business and University of the Regional Government ofAndalusia, project reference no. FEDER-UCA18-107139. Theauthors would also like to acknowledge the service from theMiNa Laboratory at IMN, and its funding from CM (projectSpaceTec, S2013/ICE2822), MINECO (project CSIC13-4E-1794), and EU (FEDER, FSE). F.P. acknowledges the supportfrom ICREA Academia 2022 and 2021SGR00242, Generalitatde Catalunya., Peer reviewed

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.