| Records |
| Author |
Sirena, M.; Kaul, E.; Pedreros, M.B.; Rodriguez, C.A.; Guimpel, J.; Steren, L.B. |
| Title |
Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers |
Type |
Journal Article |
| Year |
2011 |
Publication |
Journal of Applied Physics |
Abbreviated Journal |
J. Appl. Phys. |
Volume  |
109 |
Issue |
12 |
Pages |
123920 |
| Keywords |
atomic force microscopy; barium compounds; electrical conductivity; ferroelectric materials; ferromagnetic materials; lanthanum compounds; magnetic multilayers; magnetisation; multiferroics; sputter deposition; strontium compounds; superlattices; texture; tunnelling; X-ray diffraction |
| Abstract |
The La0.75Sr0.25MnO3 (LSMO)/Ba0.7Sr0.3TiO3 (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample’s magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions. |
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BT @ jguimpel @ |
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606 |
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Sirena, M.; Zimmers, A; Haberkorn, N.; Kaul, E.E.; Steren, L.B.; Lesueur, J.; Wolf, T.; Le Gall, Y.; Grob, J.-J.; Faini, G. |
| 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 |
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Pages |
113903 |
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no |
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BT @ ekaul @ |
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633 |
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Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. |
| 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 |
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| Volume |
105 |
Issue |
3 |
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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. |
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0021-8979 |
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ISI:000263409700057 |
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no |
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BT @ hernan @ |
Serial |
143 |
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Haberkorn, N.; Guimpel, J.; Steren, L.B.; Campillo, G.; Saldarriaga, W.; Gomez, M.E. |
| Title |
Structure of high-T-c/manganite perovskite superlattices |
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Journal Article |
| Year |
2003 |
Publication |
JOURNAL OF APPLIED PHYSICS |
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94 |
Issue |
5 |
Pages |
3011-3014 |
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We study the crystalline and interface structure of RBa2Cu3O7/La(1-x)A(x)MnO(3) superlattices (R=Y, Gd; A=Ca, Sr) grown on mismatched MgO substrates by means of nondestructive x-ray diffraction. The diffraction patterns are adjusted to a model of the structure which includes interface roughness and interdiffusion. Our results show that these disorder mechanisms cannot be neglected and should be taken into account to understand the physical properties of these superlattice. (C) 2003 American Institute of Physics. |
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0021-8979 |
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| Notes |
ISI:000184844200032 |
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no |
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BT @ hernan @ |
Serial |
167 |
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Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J. |
| Title |
Correlation between structure and magnetic properties of manganite-based multilayers |
Type |
Journal Article |
| Year |
2003 |
Publication |
JOURNAL OF APPLIED PHYSICS |
Abbreviated Journal |
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| Volume |
93 |
Issue |
10 |
Pages |
7244-7246 |
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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. |
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0021-8979 |
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ISI:000182822300273 |
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no |
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BT @ hernan @ |
Serial |
168 |
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Sirena, M.; Haberkorn, N.; Steren, L.B.; Guimpel, J. |
| 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 |
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| Volume |
93 |
Issue |
10 |
Pages |
6177-6181 |
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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. |
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0021-8979 |
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ISI:000182789700049 |
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BT @ hernan @ |
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169 |
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Steren, L.B.; Sirena, M.; Guimpel, J. |
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Substrate effect on the magnetic behavior of manganite films |
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Journal Article |
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2000 |
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JOURNAL OF APPLIED PHYSICS |
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87 |
Issue |
9 |
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6755-6757 |
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The film thickness (t) dependence of the magnetic properties of La0.6Sr0.4MnO3 (LSMO) films grown on (001) MgO and (001) SrTiO3 substrates has been studied. Hysteresis loops measured at low temperature show a smooth increase of the retentivity accompanied by a decrease of the coercitive field as the film thickness increases. The increase of coercitivity with decreasing t can be interpreted in terms of a change in the domain structure of the films mainly due to an augmentation of domain pinning defects. The magnetic anisotropy has been measured using ferromagnetic resonance (FMR). A volume (VA) and a surface (SA) anisotropy contribution have been deduced from FMR angular dependence studies for both series of samples. In the LSMO films grown on MgO a VA component that corresponds to an easy-axis perpendicular to the plane of the films has been found while in contrast, the LSMO films grown on SrTiO3 present an easy-plane anisotropy. The SA is positive for both series favoring a perpendicular magnetic anisotropy. The measured magnetic anisotropy has been assigned to substrate-induced effects. (C) 2000 American Institute of Physics. [S0021-8979(00)55708-9]. |
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0021-8979 |
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ISI:000086728800281 |
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no |
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BT @ hernan @ |
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178 |
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Haberkorn, N.; Guimpel, J.; Sirena, M.; Steren, L.B.; Saldarriaga, W.; Baca, E.; Gomez, M.E. |
| Title |
Antiferromagnetism at the YBa2Cu3O7/La2/3Ca1/3MnO3 interface |
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Journal Article |
| Year |
2004 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
84 |
Issue |
19 |
Pages |
3927-3929 |
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The magnetic properties of a series of YBa2Cu3O7-x/La2/3Ca1/3MnO3 (YBCO/LC1/3MO) superlattices grown by dc sputtering at high oxygen pressures (3.5 mbar) show the expected ferromagnetic behavior. However, field-cooled hysteresis loops at a low temperatures show the unexpected existence of exchange bias effect associated with the existence of ferromagnetic/antiferromagnetic (AF) interfaces. The blocking temperature (T-B) is found to be thickness dependent and the exchange bias field (H-EB) is found to be inversely proportional to the ferromagnetic layer thickness, as expected. The presence of an AF material is probably associated with interface disorder and Mn valence shift toward Mn4+. (C) 2004 American Institute of Physics. |
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0003-6951 |
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ISI:000221210100069 |
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BT @ hernan @ |
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165 |
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Steren, L.B.; Sirena, M.; Guimpel, J. |
| Title |
Magnetic ordered phase in La0.6Sr0.4MnO3 ferromagnets |
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Journal Article |
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2002 |
Publication |
PHYSICAL REVIEW B |
Abbreviated Journal |
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65 |
Issue |
9 |
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The ferromagnetic phase of La0.6Sr0.4MnO3 thin films has been investigated through measurements of magnetization loops at different temperatures, zero-field-cooled and field-cooled magnetization curves obtained under different magnetic fields. We have found that the main sources of the “bulk” coercivity in manganite films are the film/substrate interface and film surface. The temperature dependence of the coercivity is described by a “strong domain-wall pinning” model, independently of the thickness and substrate. The magnetization-vs-temperature curves, measured under different magnetic fields (10 Oe<H<2.5 kOe), have been explained in terms of the magnetic hysteresis of the films. We find no evidence of glass states or of the existence of single-domain clusters, as suggested by other authors. |
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1098-0121 |
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ISI:000174547900096 |
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BT @ hernan @ |
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172 |
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Sirena, M.; Steren, L.B.; Guimpel, J. |
| Title |
Magnetic relaxation in bulk and film manganite compounds |
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Journal Article |
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2001 |
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PHYSICAL REVIEW B |
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64 |
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10 |
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We have investigated the time dependence of the magnetic and transport properties of La0.6Sr0.4MnO3 films and bulk samples. A significant magnetic aftereffect has been observed in all the samples through magnetization and resistivity measurements. The relaxation effects can be described by the addition of a logarithmic to an exponential contribution. The weight of each contribution is strongly temperature dependent, with a relaxation that is predominantly logarithmic at low temperatures (T<30 K) and exponential at high temperatures (T>100 K). As the film thickness is decreased the magnetic relaxation becomes more important and the magnetic viscosity of the system increases. These results point out the important role of structural defects in the magnetic relaxation of the samples. |
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0163-1829 |
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ISI:000170978400046 |
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BT @ hernan @ |
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173 |
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