scholarly journals Molecular-Field Approximation in the Theory of Ferromagnetic Phase Transition in Diluted Magnetic Semiconductors

2021 ◽  
Vol 66 (6) ◽  
pp. 503
Author(s):  
Yu.G. Semenov ◽  
S.M. Ryabchenko

In this pedagogical paper, the comparative analysis of two common approaches describing the ferromagnetic phase transition in diluted magnetic semiconductors (DMS) is expounded in terms of the Weiss field approximation. Assuming a finite spin polarization of the magnetic ions, the treatment of carrier-ion exchange interaction in the first order evokes a homogeneous Weiss molecular field that polarizes the spins of free carriers. In turn, this spin polarization of the free carriers exerts the effective field that may stabilize the DMS spin polarization belowa critical temperature TC. The treatment of such self-consistent spontaneous DMS magnetization can be done in terms of the spin-spin interaction independent of the inter-ion distance and the infinitesimal in thermodynamic limit. On the other hand, by additionally accounting for the second-order effects of the carrier-ion exchange interaction, we can treat a Weiss field in terms of the Ruderman–Kittel–Kasuya–Yosida indirect spin-spin interaction, which oscillates and does not disappear at finite inter-ion distances in the case of a finite concentration of carriers. These both approaches result in the same Curie temperature TC provided a non-correlated homogeneous random distribution of the localized spin moments over the sample volume. We discuss the origin of such coincidence and show when this is not a case in other more realistic models of the conducting DMSs.

2020 ◽  
Vol 34 (05) ◽  
pp. 2050020
Author(s):  
Younes Ziat ◽  
Maryama Hammi ◽  
Zakaryaa Zarhri ◽  
Charaf Laghlimi ◽  
Rachid Bouachraoui ◽  
...  

The goal of this paper is to study the effect of the small amount of molybdenum-doped [Formula: see text] on the magnetism behavior of that system. We utilized the density functional theory (DFT): DFT framework within MACHIKANEYAMA2002V09 package based on Coherent Potential Approximation (CPA). Inducing the magnetism in the diluted magnetic semiconductors (DMS) with a low dopant concentration at adequate room-temperature is a challenge, so, we restricted the Mo impurity at 2%. In addition, the small amount of Mo-doped [Formula: see text] is found optimal in many studies related to other fields. The ferromagnetic stability is observed in [Formula: see text] system, since the [Formula: see text] state of Mo element is found around the Fermi level and is 100% spin polarized, the half-metallic characteristic is useful in magnetoelectronic applications. Within the mean-field approximation (MFA) we predict the Curie temperature, as an obtained value, the [Formula: see text] K, consequently, the present system showed potential promise for real applications.


CrystEngComm ◽  
2014 ◽  
Vol 16 (13) ◽  
pp. 2584-2588 ◽  
Author(s):  
Binbin Yao ◽  
Pan Wang ◽  
Shuangming Wang ◽  
Mingzhe Zhang

The classical thermally driven transition from supermagnetic to blocked supermagnetic and quantum phase transition from magnetic long-range order to quantum superparamagnetic state have been observed in ultrasmall In2S3:Ce diluted magnetic semiconductors.


2010 ◽  
Vol 168-169 ◽  
pp. 404-407
Author(s):  
E.A. Zvereva ◽  
O.A. Savelieva ◽  
S. Ibragimov ◽  
E. Samokhvalov ◽  
E.I. Slynko ◽  
...  

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.


ChemInform ◽  
2000 ◽  
Vol 31 (44) ◽  
pp. no-no
Author(s):  
T. Dietl ◽  
J. Cibert ◽  
P. Kossacki ◽  
D. Ferrand ◽  
S. Tatarenko ◽  
...  

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