The Study Of Spin Glass State In Diluted Magnetic Materials And Semiconductors Using Monte Carlo Method And Theoretical Analysis

Spin glass system is a complex disordered system with a number of local minimarnseparated by entropic barriers. Therefore, Parallel tempering Monte Carlo simulationrnwas used in order to get fast thermalisation (to minimize the relaxation time).rnDistance dependent interaction coupling in 2D is studied in order to show how arnspin glass phase transition occurs when couplings between far away spins are permittedrnby considering Edwards-Anderson Ising spin glass model. The interactionrncoupling is a quenched random variable whose probability of being non-zero decaysrnwith distance between two spin sites rij = |i−j|mod(L/2). The interaction couplingrnis random and its probability distribution is decaying with the distance between thernspins (p(Jij) / r− ). The model is studied by changing among three differentrnregimes ( > 2D, 4/3D < < 2D, < 4/3D) . A phase transition temperature forrn = 2, 3, 4 is obtained.rnIn the present work, the possibility of existence of spin glass phase using classicalrnHeisenberg model with Edwards-Anderson type of interactions has been exploredrnemploying Monte Carlo simulation of Binder parameter (g (L, T)). Previous experimentalrnstudies show that there is finite temperature phase transition but this studyrnindicates that there is no finite temperature phase transition in 3D Heisenberg vectorrnspin glass model.rnIn the dissertation we also explore magnetic properties especially spin glass state,rnantiferromagnetic state and paramagnetic state of diluted magnetic semiconductorsrn(A1−xMnxA0(A = Zn,Cd and A0 = S, Te, Se)) at critical region using classicalrnHeisenberg spin model with high temperature series expansion extrapolated withrnviirnpad´e approximants. The critical exponents associated with magnetic susceptibilityrn(rn ' 1.38 ± 0.1) and correlation function ( ' 0.8 ± o.1) were also obtained

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