Mobility of Charge Carriers in Dilute Magnetic Semiconductors

2007 ◽  
Vol 999 ◽  
Author(s):  
Michael G. Foygel ◽  
James Niggemann ◽  
A. G. Petukhov
Keyword(s):  
Magnetic Field ◽  
Electrical Transport ◽  
Magnetic Semiconductors ◽  
Magnetic Moments ◽  
Dilute Magnetic Semiconductors ◽  
Charge Carriers ◽  
Spin Fluctuations ◽  
Magnetic Impurities ◽  
Mobility Of Charge Carriers ◽  
The Magnetic Field

AbstractWe studied electrical transport in dilute magnetic semiconductors, which is determined by scattering of free carriers by localized magnetic moments. In our calculations of the scattering time and the mobility of the majority and minority-spin carriers we took into account both the effects of thermal spin fluctuations and of built-in spatial disorder of the magnetic atoms. These effects are responsible for the magnetic-field dependence of the mobility of the charge carriers. The application of the external magnetic field suppresses the thermodynamic spin fluctuations thus increasing the mobility. Simultaneously, depending on the type of the carriers and on parameters of the impurity potential, scattering by built-in spatial fluctuations of the atomic spins increases or decreases with the magnetic field. The latter effect is due to the change in the magnitude of the random local Zeeman splitting with the magnetic field. We discuss the role of the above effects on mobility and magnetoresistance of semiconductors where magnetic impurities are electrically active or neutral.

scholarly journals MAGNETIC-FIELD-INDUCED SUPERCONDUCTIVITY IN LAYERED ORGANIC MOLECULAR CRYSTALS WITH LOCALIZED MAGNETIC MOMENTS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3071-3071
Author(s):  
O. CEPAS ◽  
R. H. MCKENZIE ◽  
J. MERINO
Keyword(s):  
Magnetic Field ◽  
Superconducting State ◽  
Magnetic Moments ◽  
Spin Fluctuations ◽  
Zero Field ◽  
Field Range ◽  
Organic Molecular Crystals ◽  
Magnetic Ions ◽  
The Magnetic Field

The synthetic organic compound λ (BETS) 2 FeCl 4 undergoes successive transitions from an antiferromagnetic insulator to a metal and then to a superconductor as a magnetic field is increased. We use a Hubbard-Kondo model to clarify the role of the Fe 3+ magnetic ions in these phase transition. In the high-field regime, the magnetic field acting on the electron spins is compensated by the exchange field He due to the magnetic ions. This suggests that the field-induced superconducting state is the same as the zero-field superconducting state which occurs under pressure or when the Fe 3+ ions are replaced by non-magnetic Ga 3+ ions. We show how Hc can be extracted from the observed splitting of the Shybnikov-de Haas frequencies. Furthermore, we use this method of extracting He to predict the field range for field-induced superconductivity in other materials. We also show that at high fields the spin fluctuations of the localized spins are not important.

Infinite solitons in ferromagnetic materials with an internal magnetic field

2021 ◽  
pp. 2150413
Author(s):  
Hamdy I. Abdel-Gawad
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
External Field ◽  
Model Equation ◽  
Graphical Representation ◽  
Magnetic Moments ◽  
Soliton Solutions ◽  
Internal Magnetic Field ◽  
Multiple Soliton Solutions ◽  
The Magnetic Field

The ferromagnetism induced by an external magnetic field (EMF), in (3+1) dimensions, is governed by Kraenkel–Manna–Merle system (KMMS). A (1+1) dimension model equation was derived in the literature. The magnetic moments are parallel to the magnetic field in ferromagnetism as they are aligning in the same direction of the external field. Here, it is shown that the KMMS supports the presence of internal magnetic field. This may be argued to medium characteristics. The objective of this work is to mind multiple soliton solutions, which are obtained via the generalized together with extended unified methods. Graphical representation of the results are carried. They describe infinite soliton shapes, which arise from the multiple variation of the arbitrary functions in the solutions. It is, also, shown that internal magnetic field decays, asymptotically, to zero with time.

Manganese-Doped CdGeAs2, ZnGeAs2 and ZnSiAs2 Chalcopyrites: A New Advanced Materials for Spintronics

2010 ◽  
Vol 168-169 ◽  
pp. 31-34 ◽  
Author(s):  
A.S. Morozov ◽  
L.A. Koroleva ◽  
D.M. Zashchirinskii ◽  
T.M. Khapaeva ◽  
S.F. Marenkin ◽  
...  
Keyword(s):  
Room Temperature ◽  
Magnetic Semiconductors ◽  
Dilute Magnetic Semiconductors ◽  
Charge Carriers ◽  
Advanced Materials ◽  
Temperature Dependences ◽  
P Type ◽  
Mn Doped ◽  
Curie Temperatures ◽  
Exchange And Superexchange Interactions

Based on the Mn-doped chalcopyrites CdGeAs2, ZnGeAs2 and ZnSiAs2, new dilute magnetic semiconductors with the p-type conductivity were produced. Magnetization, electrical resistivity and Hall effect of these compositions were studied. Their temperature dependences of magnetization are similar in form in spite of a complicated character, which is controlled by the concentration and mobility of the charge carriers. Thus, for T < 15 K, these curves are characteristic of superparamagnets and for T > 15 K, of a frustrated ferromagnet. In compounds with Zn these two states are diluted by a spinglass-like state. This specific feature is ascribed to attraction of Mn ions occupying neighboring sites and to competition between the carrier-mediated exchange and superexchange interactions. The Curie temperatures of these compounds are above room temperature. These are the highest Curie temperatures in the AIIBIVCV2:Mn systems.

The Faraday effect in dilute magnetic semiconductors in ultrahigh magnetic field

1993 ◽  
Vol 29 (6) ◽  
pp. 3422-3424 ◽  
Author(s):  
P.I. Nikitin ◽  
O.M. Tatzenko ◽  
V.V. Platonov ◽  
A.I. Savchuk ◽  
S. Nikitin
Keyword(s):  
Magnetic Field ◽  
Faraday Effect ◽  
Magnetic Semiconductors ◽  
Dilute Magnetic Semiconductors ◽  
Ultrahigh Magnetic Field

Metamagnetic Transitions and Stepwise GMR in Uniaxial Fe/Cr Superlattices

2006 ◽  
Vol 52 ◽  
pp. 104-109
Author(s):  
V.V. Ustinov ◽  
L.N. Romashev ◽  
M.A. Milyaev ◽  
T.P. Krinitsina ◽  
A.M. Burkhanov
Keyword(s):  
Magnetic Field ◽  
Comparative Analysis ◽  
Easy Axis ◽  
Magnetic Moments ◽  
Film Plane ◽  
Qualitative Information ◽  
Spin Flip ◽  
Plane Anisotropy ◽  
The Magnetic Field ◽  
Mgo Substrate

We investigated the structure, magnetic and magnetoresistive properties of antiferromagnetically coupled [Fe(85Å)/Cr(tCr)]12 superlattices with the Cr layers thickness tCr = 12.4 and 13.6 Å, grown simultaneously on (100)MgO and (211)MgO substrates. It is shown that the (211)MgO substrate is appropriate for the growth of (210)Fe/Cr multilayers with a strong uniaxial in-plane anisotropy. The stepwise behavior of magnetization and magnetoresistance is revealed in the case when the magnetic field is applied along the easy axis in a film plane of (211)MgO/[(210)Fe/Cr]12 superlattices. The steps on M(H) and ΔR(H)/R dependences are caused by the flip of the magnetic moments of individual Fe layers. The qualitative information about the sequence of spin-flip transitions is extracted from the comparative analysis of magnetization and magnetoresistance data.

3D Monte Carlo Simulations of Aggregate Structures in a Magnetic Colloidal Suspension Composed of Plate-Like Particles With Magnetic Moment Normal to the Particle Axis

2010 ◽  
Author(s):  
Yasuhiro Sakuda ◽  
Masayuki Aoshima ◽  
Akira Satoh
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Applied Magnetic Field ◽  
Magnetic Moment ◽  
Magnetic Particle ◽  
Colloidal Suspension ◽  
Magnetic Moments ◽  
Particle Interactions ◽  
Aggregate Structures ◽  
The Magnetic Field

We have investigated the internal aggregate structures of a colloidal suspension composed of magnetic plate-like particles with a magnetic moment normal to the particle axis by means of three-dimensional Monte Carlo simulations. In concrete, we have attempted to clarify the influences of the magnetic field strength, magnetic interactions between particles, and volumetric fraction of particles, on particle aggregation phenomena. In order to discuss quantitatively the aggregate structures of particles, we have focused on the radial distribution and orientational pair correlation function. For no applied magnetic field cases, long column-like clusters are formed as magnetic particle-particle interactions increase. Characteristics of these clusters are that particles incline in a certain direction with their magnetic moments alternating in direction between the neighboring particles. For applied magnetic field cases, the magnetic moments of the particles incline in the magnetic field direction, so that the columnar clusters are not formed. The brick wall-like aggregates are formed as the influences of the magnetic field and magnetic particle-particle interactions become significantly dominant.

Performance Evaluation of an MR-Compatible Rotating Anode X-Ray Tube

2013 ◽  
Author(s):  
Mihye Shin ◽  
Prasheel Lillaney ◽  
Waldo Hinshaw ◽  
Rebecca Fahrig
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Moments ◽  
X Ray ◽  
Close Proximity ◽  
Motor Design ◽  
Design Requirements ◽  
And Performance ◽  
The Magnetic Field ◽  
Lorentz Force Law

The key technical innovation needed for close proximity hybrid x-ray/MR (XMR) imaging systems is a new rotating anode x-ray tube motor that can operate in the presence of strong magnetic fields. In order for the new motor design to be optimized between conflicting design requirements, we implemented a numerical model for evaluating the dynamics of the motor. The model predicts the amount of produced torque, rotation speed, and time to accelerate based on the Lorentz force law; the motor is accelerated by the interaction between the magnetic moments of the motor wire loops and an external magnetic field. It also includes an empirical model of bearing friction and electromagnetic force from the magnetic field. Our proposed computational model is validated by experiments using several different magnitudes of external magnetic fields, which averagely shows an agreement within 0.5 % error during acceleration. We are using this model to improve the efficiency and performance of future iterations of the x-ray tube motor.

scholarly journals The Characteristic Properties of Magnetostriction and Magneto-Volume Effects of Ni2MnGa-Type Ferromagnetic Heusler Alloys

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3655 ◽  
Author(s):  
Sakon ◽  
Yamasaki ◽  
Kodama ◽  
Kanomata ◽  
Nojiri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Fluctuation ◽  
Heusler Alloys ◽  
Spin Fluctuations ◽  
Fluctuation Theory ◽  
Itinerant Electron ◽  
Valence Electron Concentration ◽  
Lattice Softening ◽  
The Magnetic Field ◽  
Volume Effects

In this article, we review the magnetostriction and magneto-volume effects of Ni2MnGa-type ferromagnetic Heusler alloys at the martensitic, premartensitic, and austenitic phases. The correlations of forced magnetostriction (ΔV/V) and magnetization (M), using the self-consistent renormalization (SCR) spin fluctuation theory of an itinerant electron ferromagnet proposed by Takahashi, are evaluated for the ferromagnetic Heusler alloys. The magneto-volume effect occurs due to the interaction between the magnetism and volume change of the magnetic crystals. The magnetic field-induced strain (referred to as forced magnetostriction) and the magnetization are measured, and the correlation of magnetostriction and magnetization is evaluated. The forced volume magnetostriction ΔV/V at the Curie temperature, TC is proportional to M4, and the plots cross the origin point; that is, (M4, ΔV/V) = (0, 0). This consequence is in good agreement with the spin fluctuation theory of Takahashi. An experimental study is carried out and the results of the measurement agree with the theory. The value of forced magnetostriction is proportional to the valence electron concentration per atom (e/a). Therefore, the forced magnetostriction reflects the electronic states of the ferromagnetic alloys. The magnetostriction near the premartensitic transition temperature (TP) induces lattice softening; however, lattice softening is negligible at TC. The forced magnetostriction at TC occurs due to spin fluctuations of the itinerant electrons. In the martensitic and premartensitic phases, softening of the lattice occurs due to the shallow hollow (potential barrier) of the total energy difference between the L21 cubic and modulated 10M or 14M structures. As a result, magnetostriction is increased by the magnetic field.

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