DILUTED FERROMAGNETIC SEMICONDUCTORS — ORIGIN OF MAGNETIC ORDERING AND SPIN-TRANSPORT PROPERTIES

2008 ◽  
Vol 22 (01n02) ◽  
pp. 104-105 ◽  
Author(s):  
TOMASZ DIETL
Keyword(s):  
Diluted Magnetic Semiconductors ◽  
Spin Transport ◽  
Correlation Energy ◽  
Tight Binding ◽  
Spin Current ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Ferromagnetic Phase ◽  
Magnetic Characteristics ◽  
Ferromagnetic Semiconductors

In the first hour of the lecture the present understanding of the origin of exchange interaction and mechanisms leading to ferromagnetic order in diluted magnetic semiconductors will be presented.1 The lecture will start by discussing energy positions of relevant open magnetic shells, including the correlation energy and excitations within the magnetic ions. The origin and magnitude of sp–d exchange interactions will then be described. This will be followed by presenting the physics of indirect exchange interactions between localized spins contrasting magnetic characteristics in the absence and in the presence of free carriers. The Zener and RKKY models of ferromagnetism will be introduced and the role of confinement, dimensionality, and spin-orbit interaction in determining properties of the ferromagnetic phase will be outlined. The second lecture will be devoted to theory of spin transport in layered structures of diluted ferromagnetic semiconductors, emphasizing the issues important for perspective spintronics devices. A recently developed theory,2 which combines a multi-orbital empirical tight-binding approach with a Landauer–Büttiker formalism will be presented. In contrast to the standard kp method, this theory describes properly the interfaces and inversion symmetry breaking as well as the band dispersion in the entire Brillouin zone, so that the essential for the spin-dependent transport Rashba and Dresselhaus terms as well as the tunneling via k points away from the zone center are taken into account. The applicability of this model for the description of tunneling magnetoresistance (TMR), resonant tunneling spectra, spin-current polarization in Esaki-Zener diodes, and domain-wall resistance will be presented. Note from Publisher: This article contains the abstract only.

ESR Study of Novel Room-Temperature Ferromagnetic Semiconductors Pb1-X-YSnxCryTe

2010 ◽  
Vol 168-169 ◽  
pp. 404-407
Author(s):  
E.A. Zvereva ◽  
O.A. Savelieva ◽  
S. Ibragimov ◽  
E. Samokhvalov ◽  
E.I. Slynko ◽  
...  
Keyword(s):  
Room Temperature ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Ordering ◽  
Esr Spectra ◽  
Chromium Concentration ◽  
Ferromagnetic Phase ◽  
Wide Range ◽  
Diluted Magnetic ◽  
Ordering Transition

We report on the magnetic properties of novel diluted magnetic semiconductors Pb1 x ySnxCryTe revealing ferromagnetism at temperatures higher than room temperature. Depending on chromium concentration the Curie temperature varies in a wide range (150360 K) and effective magnetic moment achieves 1 B upon an increase of chromium doping level. Electron spin resonance (ESR) spectra in the paramagnetic phase were satisfactory approximated by a single Dysonian line. Effective g-factor tends to the saturation value g=2.080.01, while the linewidth passes through a minimum in the vicinity of magnetic ordering transition and then broadens with an increase of the temperature. In ferromagnetic phase the pronounced distortion and splitting of the ESR spectra into two lines occurs due to additional ferromagnetic contribution to absorption.

Exchange interactions and the nature of magnetic ordering in Zn0.6Mn2.4O4 particles

2020 ◽  
Vol 599 ◽  
pp. 412460
Author(s):  
N. Rajeesh Kumar ◽  
R. Kalai Selvan ◽  
Leonid Vasylechko ◽  
P. Saravanan ◽  
Mohindar S. Seehra
Keyword(s):  
Magnetic Ordering ◽  
Exchange Interactions

scholarly journals Selective spin transport through a quantum heterostructure: Transfer matrix method

2016 ◽  
Vol 30 (25) ◽  
pp. 1650184 ◽  
Author(s):  
Moumita Dey ◽  
Santanu K. Maiti
Keyword(s):  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Spin Transport ◽  
Tight Binding ◽  
Transmission Probability ◽  
Applied Bias Voltage ◽  
One Dimensional ◽  
Wide Range ◽  
Nanoscale Level

In the present work, we propose that a one-dimensional quantum heterostructure composed of magnetic and non-magnetic (NM) atomic sites can be utilized as a spin filter for a wide range of applied bias voltage. A simple tight-binding framework is given to describe the conducting junction where the heterostructure is coupled to two semi-infinite one-dimensional NM electrodes. Based on transfer matrix method, all the calculations are performed numerically which describe two-terminal spin-dependent transmission probability along with junction current through the wire. Our detailed analysis may provide fundamental aspects of selective spin transport phenomena in one-dimensional heterostructures at nanoscale level.

Ferromagnetism and Luminescence of Diluted Magnetic Semiconductors GaGdN and AlGdN

2008 ◽  
Vol 1111 ◽  
Author(s):  
Shuichi Emura ◽  
Masahiro Takahashi ◽  
Hiroyuki Tambo ◽  
Akira Suzuki ◽  
Tetsuya Nakamura ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Circular Dichroism ◽  
Peak Position ◽  
Magnetic Characteristics ◽  
Sharp Line ◽  
X Ray ◽  
Diluted Magnetic ◽  
X Ray Absorption

AbstractThe magnetic characteristics of the dilute magnetic system GaGdN are investigated by mainly soft-X-ray magnetic circular dichroism (MCD) in energy range of 1160 – 1240 eV. The strong MCD signals up to 30 % at 15K are observed. The temperature dependence of its intensity is not on simple Curie-Weiss curve and depicts three-step curve. A step around 40 – 100K suggests a new magnetic phase. The luminescence spectrum of GaGdN at low temperature is divided into three parts consisting of two broad bands around 432 nm and 503 nm and a sharp peak at 652 nm. This sharp line is assigned to the intra-transition of f – f orbital owing to the weak temperature dependence of the intensity and peak position. AlGdN grown by molecular beam epitaxy produces luminescence at 318.5 nm. X-ray absorption fine structure is examined to survey the occupancy of the Gd ion in the grown specimens.

scholarly journals Spin transport and spin dynamics in antiferromagnets

2021 ◽  
Author(s):  
◽  
Geert Hoogeboom
Keyword(s):  
Magnetic Field ◽  
Heavy Metal ◽  
Spin Transport ◽  
Spin Dynamics ◽  
Magnetic Moments ◽  
Spin Current ◽  
Active Role ◽  
Metal Films ◽  
Alternating Direction ◽  
High Processing

Ferromagnets (FMs) have been a key ingredient in information technology because it is easy to manipulate and read out the magnetization. Antiferromagnets (AFMs) have magnetic moments with alternating direction resulting in negligible magnetization. This gives them high processing and device downscaling features, but this also makes it challenging to manipulate and interact with the AFM order. This thesis studies this interaction with antiferromagnets. NiO AFM order has been read out by electrically injecting spin current via the spin Hall effect in thin heavy metal films. In DyFeO3, both Dy and Fe magnetic moments, their excitation and interaction have been probed. A magnetic field lifts the degeneracy of magnetic excitations with opposite magnon spin, allowing a spin current to be detected nonlocally. The AFM order and the generation of spin current can easily be controlled by an adjacent FM. Thereby, we show that AFMs have the potential to play an active role in spintronics.

“Magnetic Exchange Interactions in Fe/TbFe Bilayers”

1987 ◽  
Vol 103 ◽  
Author(s):  
E. E. Marinero ◽  
G. S. Sprokel ◽  
H. Notarys
Keyword(s):  
Exchange Coupling ◽  
Azimuthal Angle ◽  
Depth Profiling ◽  
Ferromagnetic Layer ◽  
Exchange Interactions ◽  
Magnetic Characteristics ◽  
Magnetic Exchange ◽  
Kerr Rotation ◽  
Composition And Structure ◽  
Magnetic Exchange Coupling

ABSTRACTWe report on magnetic exchange coupling phenomena between Fe and TbFe thin films. The structures are grown utilizing D.C. magnetron sputtering from separate Tb and Fe targets and their magnetic characteristics are measured utilizing VSM and Longitudinal Kerr Rotation. In addition, Auger depth profiling and x-ray diffraction studies were conducted to study film composition and structure.Uniaxial alignment of the Fe moment in the plane of the substrate is revealed by the longitudinal Kerr measurements. The coercivity of the Fe layer varies from 19 Oe to 130 Oe depending on the azimuthal angle between the normal to the plane of the bilayer and the direction of the external field. The hysterisis loops vary in shape from rectangular in the alignment direction to S-shape in the direction orthogonal to this direction.These effects are discussed in terms of magnetic exchange coupling interactions between the ferromagnetic layer and the ferrimagnetic alloy.

scholarly journals Structural and Magnetic Properties of Mn-Based Diluted Magnetic Semiconductors and Alloys

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
A. Alsaad
Keyword(s):  
Rock Salt ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Exchange Interactions ◽  
Magnetic Interactions ◽  
Local Spin Density Approximation ◽  
Energy Minimum ◽  
Rock Salt Structure ◽  
Magnetic Exchange ◽  
Salt Structure

Direct supercell approach calculations of the magnetic exchange interactions in Mn-doped ScN was carried out in the local spin density approximation by using the muffin-tin-orbital Green's function method. We found that magnetic interactions are long range interactions and affected by the randomness, band gap corrections, and carrier concentrations. Using total energy minimization approach we found that the global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6%, the energy minimum corresponds to the rock-salt structure in disagreement with the experimentally observed tetragonal distorted rock-salt structure, known as -phase. An isostructural phase transition for alloys from MnN -phase to -ScN phase was found to occur at a hydrostatic pressure of 18 GPa. We predict above room temperature for Mn concentrations of about 10% in ScN : Mn system.

scholarly journals Plasma-Assisted Chemical Vapor Deposition of F-Doped MnO2 Nanostructures on Single Crystal Substrates

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1335
Author(s):  
Lorenzo Bigiani ◽  
Chiara Maccato ◽  
Alberto Gasparotto ◽  
Cinzia Sada ◽  
Elza Bontempi ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Data Storage ◽  
Vapor Deposition ◽  
Oxygen Deficiency ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Analytical Techniques ◽  
Structural Features ◽  
Optical Absorption Spectroscopy ◽  
Magnetic Characteristics

MnO2 nanostructures were fabricated by plasma assisted-chemical vapor deposition (PA-CVD) using a fluorinated diketonate diamine manganese complex, acting as single-source precursor for both Mn and F. The syntheses were performed from Ar/O2 plasmas on MgAl2O4(100), YAlO3(010), and Y3Al5O12(100) single crystals at a growth temperature of 300 °C, in order to investigate the substrate influence on material chemico-physical properties. A detailed characterization through complementary analytical techniques highlighted the formation of highly pure and oriented F-doped systems, comprising the sole β-MnO2 polymorph and exhibiting an inherent oxygen deficiency. Optical absorption spectroscopy revealed the presence of an appreciable Vis-light harvesting, of interest in view of possible photocatalytic applications in pollutant degradation and hydrogen production. The used substrates directly affected the system structural features, as well as the resulting magnetic characteristics. In particular, magnetic force microscopy (MFM) measurements, sensitive to the out-of-plane magnetization component, highlighted the formation of spin domains and long-range magnetic ordering in the developed materials, with features dependent on the system morphology. These results open the door to future engineering of the present nanostructures as possible magnetic media for integration in data storage devices.

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