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Studies the growth of epitaxial lanthanum-strontium-manganite thin films on buffered silicon (001) substrates. Experimental details; Results and discussion.

The control of magnetism by electric fields is an important goal for the future development of low-power spintronics. Various approaches have been proposed on the basis of either single-phase multiferroic materials or hybrid structures in which a ferromagnet is influenced by the electric field applied to an adjacent insulator (usually having a ferroelectric, piezoelectric, or multiferroic character). The electric field effect on magnetism can be driven by purely electronic or electrostatic effects or can occur through strain coupling. Here we review progress in the electrical control of magnetic properties (anisotropy, spin order, ordering temperature, domain structure) and its application to prototype spintronic devices (spin valves, magnetic tunnel junctions). We tentatively identify the main outstanding difficulties and give perspectives for spintronics and other fields. [ABSTRACT FROM AUTHOR]

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions has aroused considerable interest and development. In parallel with this endeavor, recent advances in thin-film ferroelectrics have demonstrated the possibility of achieving stable and switchable ferroelectric polarization in nanometer-thick films. This discovery opened the possibility of using thin-film ferroelectrics as barriers in magnetic tunnel junctions, thus merging the fields of magnetism, ferroelectricity, and spin-polarized transport into an exciting and promising area of novel research. Nowadays, this research has become an important constituent of a broader effort in multiferroic materials and heterostructures that involves rich fundamental science and offers a potential for applications in novel multifunctional devices. The purpose of this article is to review recent developments in ferroelectric and multiferroic tunnel junctions. Starting from the concept of electron tunneling, we first discuss the key properties of magnetic tunnel junctions and then assess key functional characteristics of ferroelectric and multiferroic tunnel junctions. We discuss the recent demonstrations of giant resistive switching observed in ferroelectric tunnel junctions and the new concept of electrically controlling the spin polarization in magnetic tunnel junctions with a ferroelectric tunnel barrier. [ABSTRACT FROM PUBLISHER]

In this paper, we show that under appropriate deposition conditions, epitaxial films of La2/3Ca1/3MnO3 can grow fully strained on SrTiO3 (STO) single-crystalline substrates up to thicknesses as large as 180 nm. In particular, the growth rate appears to be a critical parameter. The microstructure of fully strained films of different thickness values is analyzed by high-resolution transmission electron microscopy, showing sharp interfaces and no misfit dislocations. The magnetotransport properties are studied as a function of thickness. It is found that, despite the absence of steric effects related to strain relaxation, the metal-to-insulator transition temperature is reduced from 270 K for the 180 nm films to some 100 K for the thinner films thus revealing the increasing influence of the interface of the film with the substrate. [Copyright &y& Elsevier]

The authors report on the functionalization of multiferroic BiFeO3 epitaxial films for spintronics. A first example is provided by the use of ultrathin layers of BiFeO3 as tunnel barriers in magnetic tunnel junctions with La2/3Sr1/3MnO3 and Co electrodes. In such structures, a positive tunnel magnetoresistance up to 30% is obtained at low temperature. A second example is the exploitation of the antiferromagnetic spin structure of a BiFeO3 film to induce a sizable (∼60 Oe) exchange bias on a ferromagnetic film of CoFeB at room temperature. Remarkably, the exchange bias effect is robust upon magnetic field cycling, with no indications of training. [ABSTRACT FROM AUTHOR]

We report on the use of the LaAlO3 (LAO) high-k dielectric as a tunnel barrier in magnetic tunnel junctions. From tunnel magnetoresistance (TMR) measurements on epitaxial La2/3Sr1/3MnO3/LAO/La2/3Sr1/3MnO3 junctions, we estimate a spin polarization of 77% at low temperature for the La2/3Sr1/3MnO3/LAO interface. Remarkably, the TMR of La2/3Sr1/3MnO3/LAO/Co junctions at low bias is negative, evidencing a negative spin polarization of Co at the interface with LAO, and its bias dependence is very similar to that of La2/3Sr1/3MnO3/SrTiO3/Co junctions. We discuss possible reasons for this behavior. [ABSTRACT FROM AUTHOR]

We report on the use of the LaAlO3 (LAO) high-k dielectric as a tunnel barrier in magnetic tunnel junctions. From tunnel magnetoresistance (TMR) measurements on epitaxial La2/3Sr1/3MnO3/LAO/La2/3Sr1/3MnO3 junctions, we estimate a spin polarization of 77% at low temperature for the La2/3Sr1/3MnO3/LAO interface. Remarkably, the TMR of La2/3Sr1/3MnO3/LAO/Co junctions at low bias is negative, evidencing a negative spin polarization of Co at the interface with LAO, and its bias dependence is very similar to that of La2/3Sr1/3MnO3/SrTiO3/Co junctions. We discuss possible reasons for this behavior. [ABSTRACT FROM AUTHOR]

We report on the observation of magnetoresistance in a Sr[sub 2]FeMoO[sub 6] (SFMO)-based tunnel junction. This result is obtained by combining a three-step process for the growth of the Sr[sub 2]FeMoO[sub 6] layer by pulsed laser deposition with a technology allowing the definition of nanometer-sized junctions. A clear positive magnetoresistive signal of 50% is obtained at low temperature in a Sr[sub 2]FeMoO[sub 6]/SrTiO[sub 3]/Co junction. Since the SrTiO[sub 3]/Co interface is known to have a negative spin polarization of about 20%, this result yields a negative spin polarization of SFMO, which we find to amount to more than 85% in our film. This confirms the half-metallic character of this compound, predicted by band structure calculations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the epitaxial growth of magnetoresistive and thin films on (001) silicon substrates. Easy-magnetization direction within the film plane; Control of the low-field magnetoresistance by the in-plane misorientation of crystallites.

Abstract: We report on the magnetotransport properties and spin polarization of Co-doped (La,Sr)TiO3 (Co-LSTO) thin films in which the host oxide is a strongly correlated metal with a high density of carriers. In order to probe the spin polarization, we have performed tunneling magnetoresistance (TMR) measurements on magnetic tunnel junctions associating Co-LSTO and Co electrodes. A large spin polarization of around −80% has been determined at low temperatures, indicating that the carriers in this system are highly spin-polarized. We also report on the planar magnetotransport experiments on Co-LSTO films grown on SrTiO3 substrates. The electrical properties of these samples are strongly dependent on the growth conditions and large electronic mobilities as high as 104 cm2/Vs at T<10K are observed for specimens grown at the lowest oxygen pressure. We show that this high-mobility state is three-dimensional and we relate it to the doping of the SrTiO3 substrate with oxygen vacancies. [Copyright &y& Elsevier]