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Spintronics = Spin + Electronics

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Presentation on theme: "Spintronics = Spin + Electronics"— Presentation transcript:

1 Theory of Diluted Ferromagnetic III-V compound semiconductor materials of Spintronics

2 Spintronics = Spin + Electronics
The most interesting material is Diluted Ferromagnetic semiconductor III-V based with Mn impurity i.e. (In,Mn)As, (Ga,Mn)As

3 III-V DMSs : S = 5/2 (Mn 2+) hole concs. ~ 10% impurities concs. (compensated doping) hole spins couple with Mn AF (p-d coupling)

4 Compensated doping

5 Carrier mediated ferromagetism
Dilute electrons Local moments RKKY indirect interaction

6 Kondo Lattice model With Zeeman energies

7 Arbitrary S local moment Green’s function
Equation of motion The time derivative of local spin greens function

8 Where Then Through RPA mean field

9 Including spin flip Greens function of conducting electrons
equal to Through the Fourier transformation Local spin Greens function spin flip Greens function

10 Combined together

11 Self-energy Dyson’s general formula of magnetization where

12 RPA first order approx. for electrons
take the dilute limit by conversing the kinetic energy to free electrons like The summation becomes

13 Spinwave Spectrum where

14 for By L’Hospital rule

15 Imaginary part of self energy will cause the spin waves spread
The delta function made a constraint the existing region for the imaginary part

16 Considering the zero temperature situation
the existing region for the imaginary part

17 From Dyson’s general formula of magnetization
Magnetization profile is comparable for Monte Carlo result for Ising interaction(Osamu Sakai, Physica E 10,148(2001)

18 To evaluate the temperature dependence of static susceptibility,
Where and are expectation values of local spin with magnetic field turned on and off

19 Conclusions: Kondo lattice model utilizes the equation of motion method with RPA approximation in dilute limitation to obtain a local spin greens function of self consistent solution can well describe the magnetic properties of diluted ferromagnetic semiconductors

20 From examining the imaginary part of self energy reveals that the spin excitations are well established in this model The temperature dependence of magnetization is qualitatively consistent with Monte Carlo result the significant peak of susceptibility appearing before Tc agrees with experimental result


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