Effects of dilution and disorder on magnetism in diluted spin systems

Abstract

The influence of configurational disorder on the magnetic properties of diluted Heisenberg spin systems is studied with regard to the ferromagnetic stability of diluted magnetic semiconductors. The equation of motion of the magnon Green's function is decoupled by Tyablikov approximation. With supercell approach, the concentrations of magnetic ions are determined by the size of the supercell in which there is only one magnetic ion per supercell in our method. In order to distinguish the influence of dilution and disorder, there are two kinds of supercells being used: the \textit{diluted and ordered} case and the \textit{diluted and disordered} case. The configurational averaging of magnon Green function due to disorder is treated in the augmented space formalism. The random exchange integrals between two supercells are treated as a matrix. The obtained magnon spectral densities are used to calculate the temperature dependence of magnetization and Curie temperature. The results are shown as following: (i) dilution leads to increasing the averaged distance of two magnetic ions, further decreases the effective exchange integrals and is main reason to reduce Curie temperature; (ii) spatial position disorder of magnetic ions results in the dispersions of the exchange integrals between two supercells and slightly changes ferromagnetic transition temperature; (iii) the exponential damping of distance dependence obviously reduces Curie temperature and should be set carefully in any phenomenological model.

8 pages, 3 figures, accepted by physica status solidi (b); added references and the corresponding remarks

References in corpus (5)

• Boundary effects in the critical scaling of entanglement entropy in 1D systems
• Why RKKY exchange integrals are inappropriate to describe ferromagnetism in diluted magnetic semiconductors
• Disorder in Diluted Spin Systems
• Positional Disorder, Spin-Orbit Coupling and Frustration in GaMnAs
• Exchange anisotropy, disorder and frustration in diluted, predominantly ferromagnetic, Heisenberg spin systems

Cited by in corpus (5)

• Magnetic phases in the correlated Kondo-lattice model
• Theory of spin waves in ferromagnetic (Ga,Mn)As
• The influence of structural short-range order on the phase diagrams of diluted FCC magnet with arbitrary spin and modified RKKY interaction
• Kosterlitz-Thouless transition in disordered two-dimensional topological insulators
• Spin-wave theory in a randomly disordered lattice: A Heisenberg ferromagnet