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|Type:||Artigo de periódico|
|Title:||Magnetic Properties Of Gan Mnx Ga1-x N Digital Heterostructures: First-principles And Monte Carlo Calculations|
|Abstract:||The energetic and magnetic properties of wurtzite GaN Mnx Ga1-x N digital heterostructures are investigated by first-principles total energy calculations, within the spin density-functional theory, and Monte Carlo simulations. In a wurtzite GaN model sample, periodic in the c axis, we replace a GaN monolayer (a plane) by a plane with composition Mnx Ga1-x N, and study its properties for varying the GaN spacer layer thickness and Mn concentration x. The 100% MnN monolayer possesses an antiferromagnetic (AFM) ground state when, in the periodic sample, it is isolated from the other MnN monolayers by more than four GaN spacer layers. The case of submonolayers (x<1) is studied by Monte Carlo simulations based on an Ising Hamiltonian, whose parameters are obtained from ab initio calculations on five configurations. At 700°C, up to the concentration of 8% Mn, the two-dimensional (2D) alloy is stable. However, above this concentration, there is a strong tendency to the formation of MnN clusters with an AFM ground state defined by ferromagnetic Mn rows coupled antiferromagnetically with other Mn rows. The behavior of the magnetization with the temperature is completely different in these two concentration regimes, with the 2D MnN cluster being very stable, whereas the 2D alloy presents low magnetic transition temperatures. © 2006 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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