Sub-200 Oe Giant Magnetoresistance in Manganite Tunnel Junctions

1997 ◽  
Vol 494 ◽  
Author(s):  
Gang Xiao ◽  
A. Gupta ◽  
X. W. Li ◽  
G. Q. Gong ◽  
J. Z. Sun
Keyword(s):  
Electronic Structure ◽  
Colossal Magnetoresistance ◽  
Giant Magnetoresistance ◽  
Domain Walls ◽  
Tunnel Junctions ◽  
Research Effort ◽  
Boundary Effect ◽  
Magnetic Domain ◽  
Magnetic Ordering ◽  
Dependent Transport

ABSTRACTMetallic manganite oxides, La1-xDxMnO3 (D=Sr, Ca, etc.), display “colossal” magnetoresistance (CMR) near their magnetic phase transition temperatures (Tc) when subject to a Tesla-scale magnetic field. This phenomenal effect is the result of the strong interplay inherent in this class of materials among electronic structure, magnetic ordering, and lattice dynamics. Though fundamentally interesting, the CMR effect achieved only at large fields poses severe technological challenges to potential applications in magnetoelectronic devices, where low field sensitivity is crucial. Among the objectives of our research effort involving manganite materials is to reduce the field scale of MR by designing and fabricating tunnel junctions and other structures rich in magnetic domain walls. The junction electrodes were made of doped manganite epitaxial films, and the insulating barrier of SrTiO3. The interfacial expitaxy has been imaged by using high-resolution transmission electron microscopy (TEM). We have used self-aligned lithographic process to pattern the junctions to micron scale in size. Large MR values close to 250% at low fields of a few tens of Oe have been observed. The mechanism of the spin-dependent transport is due to the spin-polarized tunneling between the half-metallic electrodes, in which the spins of the conduction electrons are nearly fully polarized. We will present results of field and temperature dependence of MR in these structures and discuss the electronic structure of the manganite inferred from tunneling measurement. Results of large MR at low fields due to the grain-boundary effect will also be presented.

Electronic Structure Transformation in a Magnetized Topological Semimetal

2021 ◽  
Vol 1 ◽  
Keyword(s):  
Electronic Structure ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Localized States ◽  
Structure Transformation ◽  
Nodal Lines ◽  
Topological Semimetal ◽  
Magnetic Domain Walls ◽  
Magnetic Orders ◽  
Topological Semimetals

We theoretically show that the nodal structures in topological semimetals, including Weyl points and nodal lines, can be switched by magnetic orders, accompanied by localized states at magnetic domain walls.

Interplay Between Electronic Transport and Magnetic Order in Ferromagnetic Manganite Thin Films

1997 ◽  
Vol 474 ◽  
Author(s):  
M. R. Hundley ◽  
J. J. Neumeier ◽  
R. H. Heffher ◽  
Q. X. Jia ◽  
X. D. Wu ◽  
...  
Keyword(s):  
Thin Films ◽  
Electronic Transport ◽  
Transition Metal Oxides ◽  
Colossal Magnetoresistance ◽  
Magnetic Order ◽  
Magnetic Ordering ◽  
Temperature Dependent ◽  
Sharp Maximum ◽  
Magnetic Ordering Temperature ◽  
Dependent Transport

ABSTRACTThe transition metal oxides La1-xAxMnO3 (A = Ba, Ca, or Sr) order ferromagnetically with Curie temperatures ranging from as low as 50 K to well above room temperature. Magnetic order in these compounds results in a concomitant metal-insulator transition. The feature displayed by the manganites that is most important technologically is the extremely large negative magnetoresistance that achieves its largest values near the magnetic ordering temperature. Qualitatively, this colossal magnetoresistance (CMR) phenomenon involves the suppression of the relatively sharp maximum in the resistivity that is centered at Tc. When considered collectively, the anomalous temperature-dependent transport properties, the CMR effect, and the magnetically ordered ground state indicate that a novel interplay between magnetism and electronic transport occurs in the manganites. General features of the magnetic-field and temperature-dependent electrical resistivity and magnetization as displayed by PLD-grown thin films are examined. Particular emphasis is placed on what these measurements tell us about the conduction process both above and below the magnetic ordering temperature.

The direct determination of magnetic domain wall profiles using a split detector STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 466-467
Author(s):  
J.N. Chapman ◽  
P.E. Batson ◽  
E.M. Waddell ◽  
R.P. Ferrier
Keyword(s):  
Electron Microscope ◽  
Domain Wall ◽  
Transmission Electron Microscope ◽  
Domain Walls ◽  
Photographic Plate ◽  
Magnetic Domain ◽  
Direct Determination ◽  
Quantitative Information ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron

By far the most commonly used mode of Lorentz microscopy in the examination of ferromagnetic thin films is the Fresnel or defocus mode. Use of this mode in the conventional transmission electron microscope (CTEM) is straightforward and immediately reveals the existence of all domain walls present. However, if such quantitative information as the domain wall profile is required, the technique suffers from several disadvantages. These include the inability to directly observe fine image detail on the viewing screen because of the stringent illumination coherence requirements, the difficulty of accurately translating part of a photographic plate into quantitative electron intensity data, and, perhaps most severe, the difficulty of interpreting this data. One solution to the first-named problem is to use a CTEM equipped with a field emission gun (FEG) (Inoue, Harada and Yamamoto 1977) whilst a second is to use the equivalent mode of image formation in a scanning transmission electron microscope (STEM) (Chapman, Batson, Waddell, Ferrier and Craven 1977), a technique which largely overcomes the second-named problem as well.

Lorentz microscopy study of magnetic domain walls in Fe-Cr-Co alloys

1978 ◽  
Vol 36 (1) ◽  
pp. 462-463
Author(s):  
Yalcin Belli
Keyword(s):  
Domain Walls ◽  
Magnetic Domain ◽  
Microscopy Study ◽  
Ferromagnetic Phase ◽  
Stable Phase ◽  
Magnetic Domains ◽  
Lorentz Microscopy ◽  
Magnetic Hardening ◽  
Electron Microscopes ◽  
Co Alloys

Fe-Cr-Co alloys have great technological potential to replace Alnico alloys as hard magnets. The relationship between the microstructures and the magnetic properties has been recently established for some of these alloys. The magnetic hardening has been attributed to the decomposition of the high temperature stable phase (α) into an elongated Fe-rich ferromagnetic phase (α1) and a weakly magnetic or non-magnetic Cr-rich phase (α2). The relationships between magnetic domains and domain walls and these different phases are yet to be understood. The TEM has been used to ascertain the mechanism of magnetic hardening for the first time in these alloys. The present paper describes the magnetic domain structure and the magnetization reversal processes in some of these multiphase materials. Microstructures to change properties resulting from, (i) isothermal aging, (ii) thermomagnetic treatment (TMT) and (iii) TMT + stepaging have been chosen for this investigation. The Jem-7A and Philips EM-301 transmission electron microscopes operating at 100 kV have been used for the Lorentz microscopy study of the magnetic domains and their interactions with the finely dispersed precipitate phases.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Introduction of spin torques

2017 ◽  
Author(s):  
T. Kimura
Keyword(s):  
Angular Momentum ◽  
Giant Magnetoresistance ◽  
Spontaneous Magnetization ◽  
Magnetic Domain ◽  
Magnetic Multilayers ◽  
Transfer Effect ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Angular Momentum ◽  
Spin Torques

This chapter discusses the spin-transfer effect, which is described as the transfer of the spin angular momentum between the conduction electrons and the magnetization of the ferromagnet that occurs due to the conservation of the spin angular momentum. L. Berger, who introduced the concept in 1984, considered the exchange interaction between the conduction electron and the localized magnetic moment, and predicted that a magnetic domain wall can be moved by flowing the spin current. The spin-transfer effect was brought into the limelight by the progress in microfabrication techniques and the discovery of the giant magnetoresistance effect in magnetic multilayers. Berger, at the same time, separately studied the spin-transfer torque in a system similar to Slonczewski’s magnetic multilayered system and predicted spontaneous magnetization precession.

scholarly journals Phase shifter based on voltage-controlled magnetic domain walls

AIP Advances ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 075225
Author(s):  
Xiao Zhang ◽  
Chen Zhang ◽  
Chonglei Sun ◽  
Xiao Xu ◽  
Liuge Du ◽  
...  
Keyword(s):  
Phase Shifter ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Magnetic Domain Walls
Sign in / Sign up

Export Citation Format

Share Document