Chemical trends of substitutional transition-metal dopants in diamond: Anab initiostudy

Abstract

The electronic and magnetic properties of neutral substitutional transition-metal dopants in diamond are calculated within density functional theory using the generalized gradient approximation to the exchange-correlation potential. Ti and Fe are nonmagnetic, whereas the ground state of V, Cr and Mn are magnetic with a spin entirely localized on the magnetic ion. For Co, Ni, and Cu, the ground state is magnetic with the spin distributed over the transition-metal ion and the nearest-neighbor carbon atoms; furthermore a bound state is found in the gap that originates from the hybridization of the 3d-derived level of the dopant and the 2p-derived dangling bonds of the nearest-neighbor carbons. A p-d hybridization model is developed in order to describe the origin of the magnetic interaction. This model predicts high-spin to low-spin transitions for Ni and Cu under compressive strain.

HPHT growth and characterization of diamond from a copper-carbon system

“…Theoretical calculations suggested that copper would be a likely defect in diamond [21,22]. Furthermore, some interesting phenomena, such as stress-induced high-spin to low-spin transition, were recently predicted for copper paramagnetic defects in diamond [23].…”

Transition-metal dopants in tetrahedrally bonded semiconductors

“…The ratio of ground state on site spectral weight for chromium:nickel is ∼ 2:1 and the same holds for the ratio, manganese:cobalt, the spin 1/2 analog of chromium:nickel. Differing from density functional theory calculations [151], the nearest neighbor carbon local density of states for the chromium ground state is two times larger than the nickel nearest neighbor carbon local density of states. The nearest neighbor local density of states for both chromium and nickel are also significantly lower than the on site local density of states implying both of their states are localized.…”

“…This will illustrate the difficulty in discerning d(t 2 ) from d(e) dopant wavefunctions based on spatial extent of wavefunction alone. To examine which first row transition metal dopants are which symmetry type in either material we consult density functional theory calculations [150,151]. These many body calculations allow tuning of the impurity nonmagnetic and magnetic potential such that the impurity levels are positioned correctly in this tight-binding model.…”

“…These many body calculations allow tuning of the impurity nonmagnetic and magnetic potential such that the impurity levels are positioned correctly in this tight-binding model. [151] and GaAs [150]. The highest occupied level for each impurity in each material is marked with a black arrow.…”

“…The parameters are taken from reference [132], where the calculated diamond band structures are in good agreement with experiments and pseudopotential calculations. The values of the nonmagnetic and magnetic potential are set such that the impurity levels they create fit the impurity levels calculated by density functional theory for transition metal dopants [151] or the measured impurity levels of the NV − center [172]. The spin-orbit potential has been calculate from atomic energies [173] and using the Lande interval rule.…”