toggle visibility Search & Display Options

Select All    Deselect All
 |   | 
Details
   print
  Records Links
Author (up) Niebieskikwiat, D.; Haberkorn, N.; Guitarra, R.; Guimpel, J. doi  openurl
  Title Magnetic properties of SrTiO3/Pr2/3Ca 1/3MnO3 multilayers Type Conference Article
  Year 2010 Publication Journal of Physics: Conference Series Abbreviated Journal  
  Volume 200 Issue 7 Pages 072069  
  Keywords  
  Abstract Nanoscale ferromagnetic (FM) clusters embedded within insulating (I) layers of the antiferromagnetic Pr2/3Ca1/3MnO3 (PCMO) are known to improve the magnetoresistance ratio of FM-I magnetoresistive multilayers. Here, we study the magnetic properties of perovskite superlattices comprised of five PCMO layers of variable thickness t separated by 5nm-thick spacers of SrTiO3 (STO). Several multilayers (1.5 nm ≤ t ≤ 8 nm) were grown on (001) STO substrates by magnetron sputtering. We show that the magnetic moment of PCMO due to the FM inclusions presents a maximum for t ∼ 3 nm, accompanied by an abrupt increase of coercivity and exchange bias field. The nonmagnetic nature of the neighboring STO layers demonstrates that the observed behavior is not related to any interlayer exchange coupling, but the geometrical matching between layer thickness and FM domain size is the key driver for the enhancement of the FM moment and anisotropy energy. These results open a new door for the optimization of perovskite based spintronic devices.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ hernan @ Serial 602  
Permanent link to this record
 

 
Author (up) Pozo-López, G.; Condó, A.M.; Fabietti, L.M.; Winkler, E.; Haberkorn, N.; Urreta, S.E. url  doi
openurl 
  Title Microstructure of as-cast single and twin roller melt-spun Ni2MnGa ribbons Type Journal Article
  Year 2017 Publication Materials Characterization Abbreviated Journal  
  Volume 124 Issue Pages 171-181  
  Keywords Shape–memory alloys; Magnetic properties; Martensitic transformation; Rapid solidification; Microstructure; Transmission electron microscopy  
  Abstract Stoichiometric Ni2MnGa alloys are processed by two rapid solidification techniques – single-roller (SR) and twin-roller (TR) melt spinning – and the resulting microstructures and magnetic properties determined. Samples processed at tangential wheel speeds of 10m/s (V10) and 15m/s (V15) are studied in the as-cast condition to analyze the influence of the production methods on the microstructure. Important aspects like the resulting phases, their crystallographic texture, magnetic properties, martensitic transformation temperatures and Curie temperatures are compared. In addition, the magnetization mechanism involving twin boundary motion is explored. Our results indicate that the TR method provides lower cooling rates, thicker samples, higher internal stresses and larger MnS precipitates. However, the quenching rate is mainly determined by the tangential wheel velocity. TR samples also exhibit [100] texture normal to the ribbon plane but in a lesser extent than SR ribbons. Martensitic transformation temperatures are higher in samples V15 (~150K) than in V10 (~100K), with no clear difference between the SR and TR modes. This behavior is explained by considering distinct degrees of disorder in the L21 austenite phase resulting from quenching. The hysteresis of the transformation, defined as the difference Af−MS, takes similar values in the four samples analyzed. Pre-martensitic transformation temperatures are also slightly higher in samples V15, (230±3) K, than in samples V10, (222±3) K, as the magnitude of the Hopkinson effect, in good agreement with a higher residual stress level in TR ribbons. In the martensitic state, all ribbons exhibit hysteresis loops characteristic of a magnetization mechanism involving twin boundary motion. The switching magnetic fields for the onset of Type I twin boundary motion result between 220mT and 365mT, values equivalent to twinning stresses of about 1MPa. It is concluded that both procedures, SR and TR melt spinning, provide microstructures favoring magnetic field induced twin variant reorientation.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1044-5803 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 779  
Permanent link to this record
 

 
Author (up) Prieto, P.; Gomez, M.E.; Campillo, G.; Berger, A.; Baca, E.; Escudero, R.; Morales, F.; Guimpel, J.; Haberkorn, N. openurl 
  Title Exchange-coupling effect and magnetotransport properties in epitaxial La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 superlattices Type Journal Article
  Year 2004 Publication PHYSICA STATUS SOLIDI A-APPLIED RESEARCH Abbreviated Journal  
  Volume 201 Issue 10 Pages 2343-2346  
  Keywords  
  Abstract We have measured structural, magnetic and, magneto transport properties of heterostructures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x = 0.33) and antiferromagnetic (AF) layers (x = 0.67). FM/AF superlattices were grown by a high-pressure sputtering technique on (001) oriented SrTiO3 substrates. We have systematically varied the thickness of the ferromagnetic layers, while maintaining the thickness of the antiferromagnetic layers fixed. The total superlattice thickness was held approximately constant. The XRD analysis confirmed the existence of the superlattice structure by the multiple satellite peaks around the 001 manganite Bragg reflections. We have done field cooling (FC) and zero field cooling (ZFC) magnetization, and magneto resistance measurements at temperatures between 10 K and 280 K. The existence of an exchange bias effect at temperatures below the Neel temperature of the AF layer was revealed by magnetization loops after field cooling. The exchange bias field magnitude H-ex exhibited exponential temperature dependence below the blocking temperature, as well as an inverse proportionality with the ferromagnetic layer thickness. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0031-8965 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000223613800023 Approved no  
  Call Number BT @ hernan @ Serial 161  
Permanent link to this record
 

 
Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. openurl 
  Title Metal-insulator transition induced by postdeposition annealing in low doped manganite films Type Journal Article
  Year 2009 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal  
  Volume 105 Issue 3 Pages  
  Keywords  
  Abstract We studied the transport and magnetic properties of low-doped manganite films after different oxygenation processes. The oxygen content was adjusted by postdeposition annealing at different oxygen pressures and annealing times. For all the samples we observed an increase in the Curie temperature and the remnant magnetization with the oxygen content. In general, for decreasing number of oxygen vacancies, samples under expansive strain become more homogeneous and their electrical resistivity decreases. A metal-insulator transition is induced in highly oxygenated films grown on SrTiO3, probably related to a shift of the mobility edge crossing below the Fermi energy. We found that the oxygenation dynamics depend critically on the strain field induced by the substrates and also on the Sr doping concentration.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0021-8979 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000263409700057 Approved no  
  Call Number BT @ hernan @ Serial 143  
Permanent link to this record
 

 
Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. openurl 
  Title Oxygen and disorder effect in the magnetic properties of manganite films Type Journal Article
  Year 2004 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal  
  Volume 272 Issue Pages 1171-1173  
  Keywords  
  Abstract We have made a systematic study of the magnetic properties of low doped manganite films submitted to different oxygenation treatments. We have found that oxygenation dynamics depends critically of the strain field in the sample. The T-C and the Mr increase as the oxygen content is increased. A decrease of the coercive field of the LSMO-STO films was observed, indicating that annealing treatments increase the oxygen content reducing oxygen vacancies. (C) 2004 Elsevier B.V. All rights reserved.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0304-8853 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000222236700179 Approved no  
  Call Number BT @ hernan @ Serial 162  
Permanent link to this record
 

 
Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. url  openurl
  Title Oxygen and disorder effect in the magnetic properties of manganite films Type Journal Article
  Year 2004 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal Proceedings of the International Conference on Magnetism (ICM 2003)  
  Volume 272-276, Part 2 Issue Pages 1171-1173  
  Keywords Manganite fims; Oxigenation; Magnetic properties  
  Abstract We have made a systematic study of the magnetic properties of low doped manganite films submitted to different oxygenation treatments. We have found that oxygenation dynamics depends critically of the strain field in the sample. The TC and the Mr increase as the oxygen content is increased. A decrease of the coercive field of the LSMO-STO films was observed, indicating that annealing treatments increase the oxygen content reducing oxygen vacancies.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0304-8853 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ jguimpel @ Serial 622  
Permanent link to this record
 

 
Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. openurl 
  Title Correlation between structure and magnetic properties of manganite-based multilayers Type Journal Article
  Year 2003 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal  
  Volume 93 Issue 10 Pages 7244-7246  
  Keywords  
  Abstract We have studied the structure, magnetic, and transport properties of manganite-based multilayers A/B-i, with A=La0.55Sr0.45MnO3 (metallic ferromagnet), and spacers (B-i) of different nature: B-1=SrTiO3 (nonmagnetic insulator), B-2=La0.9Sr0.1MnO3 (insulator ferromagnet), and B-3=La0.67Ca0.33MnO3 (paramagnetic-insulator/ferromagnet-metal). The samples are strongly textured in the direction perpendicular to the sample surface, and present a good interface quality with small roughness and interdiffusion. We have found that in the A/B-1/A trilayers, the ferromagnetic electrodes are ferromagnetically coupled for thin spacer layers and becomes decoupled for spacer thickness larger than 3 nm. Instead, the others multilayers are ferromagnetic for all spacer thicknesses and temperature range. This result was expected for temperatures well below the spacer Curie temperature. We attributed the ferromagnetic behavior of the system, found for temperatures above the ordering temperature of the spacer, to direct exchange coupling through short-range ordered zones in spacer layer. As expected from magnetization results, in fact, no extrinsic magnetoresistance was measured in these systems in the temperature range between 4.2 and 300 K. (C) 2003 American Institute of Physics.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0021-8979 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000182822300273 Approved no  
  Call Number BT @ hernan @ Serial 168  
Permanent link to this record
 

 
Author (up) Sirena, M.; Haberkorn, N.; Steren, L.B.; Guimpel, J. openurl 
  Title Magnetic coupling and magnetoresistance in La0.55Sr0.45MnO3/La0.67Ca0.33MnO3 multilayers Type Journal Article
  Year 2003 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal  
  Volume 93 Issue 10 Pages 6177-6181  
  Keywords  
  Abstract We have studied the interlayer coupling and the magnetoresistant effect of La0.55Sr0.45MnO3/La0.67Ca0.33MnO3 structures. Magnetization loops, measured in La0.55Sr0.45MnO3/La0.67Ca0.33MnO3/La0.55Sr0.45MnO3 trilayers, indicate that there is a ferromagnetic coupling of the La0.55Sr0.45MnO3 layers across the La0.67Ca0.33MnO3 spacer up to room temperature, even above the Curie temperature of the La0.67Ca0.33MnO3 layers. However, magnetization versus temperature curves present signatures of the magnetic ordering of both compounds. No extrinsic magnetoresistance associated with the multilayered structure was observed in the whole temperature range due to the presence of the interlayer ferromagnetic coupling. (C) 2003 American Institute of Physics.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0021-8979 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000182789700049 Approved no  
  Call Number BT @ hernan @ Serial 169  
Permanent link to this record
 

 
Author (up) Sirena, M.; Zimmers, A; Haberkorn, N.; Kaul, E.E.; Steren, L.B.; Lesueur, J.; Wolf, T.; Le Gall, Y.; Grob, J.-J.; Faini, G. openurl 
  Title Direct observation of electronic inhomogeneities induced by point defect disorder in manganite films Type Journal Article
  Year 2010 Publication Journal of Applied Physics Abbreviated Journal JAP  
  Volume 107 Issue Pages 113903  
  Keywords  
  Abstract  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ ekaul @ Serial 633  
Permanent link to this record
 

 
Author (up) Sutter, J.G.; Chávez, A.S.; Soria, S.; Granada, M.; Neñer, L.; Bengió, S.; Granell, P.; Golmar, F.; Haberkorn, N.; Leyva, A.G.; Sirena, M. url  doi
openurl 
  Title Tuning the magneto-electrical properties of multiferroic multilayers through interface strain and disorder Type Journal Article
  Year 2020 Publication Journal of Alloys and Compounds Abbreviated Journal J. Alloys Compd.  
  Volume Issue Pages 157820  
  Keywords multiferroic; superlattices; manganites; magnetism; disorder  
  Abstract Artificially engineered superlattices were designed and fabricated to induce different growth mechanisms and structural characteristics. DC sputtering was used to grow ferromagnetic (La0.8Ba0.2MnO3)/ferroelectric (Ba0.25Sr0.75TiO3 or BaTiO3) superlattices. We systematically modified the thickness of the ferromagnetic layer to analyze dimensional and structural disorder effects on the superlattices with different structural characteristics. The crystalline structure was characterized by X-ray diffraction and transmission electron microscopy. The magnetic and electronic properties were investigated by SQUID magnetometry and resistance measurements. The results show that both strain and structural disorder can significantly affect the physical properties of the systems. Ba0.25Sr0.75TiO3 based superlattices with a low thickness of the ferromagnetic layers (4 nm.) present compressive strain that decreases the ferromagnetic transition temperature from 250 K corresponding to the unstressed samples to 230 K. In these samples, the localization energy of the charge carrier through the electron-phonon interaction decreases at low temperatures (∼100 meV). Ba0.25Sr0.75TiO3 based superlattices with thicknesses of the ferromagnetic layers higher than 12 nm present tensile strain that reduces the charge carrier localization energy at low temperatures (∼1 meV), increasing the ferromagnetic transition temperature (Tc∼265K). Structural defects in BaTiO3 based superlattices have a stronger influence on the magnetic properties than on the transport properties. Nevertheless, disorder blocks the ferromagnetic transition for highly disordered samples (thickness of the ferromagnetic layer < 3 nm). These results help to further understand the role of strain and interface effects in the magnetic and transport properties of manganite based multiferroic systems.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0925-8388 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number BT @ pedrazp @ Serial 861  
Permanent link to this record
Select All    Deselect All
 |   | 
Details
   print

Save Citations:
Export Records: