Is manganese-doped diamond a ferromagnetic semiconductor?

TL;DR

This study uses density-functional theory to evaluate the magnetic properties of Mn-doped diamond, challenging previous predictions of high-temperature ferromagnetism and finding it unlikely due to energetic and electronic factors.

Contribution

It provides a detailed theoretical analysis showing that Mn-doped diamond is unlikely to be a ferromagnetic semiconductor at high temperatures, contradicting earlier mean-field predictions.

Findings

Substitutional Mn in diamond has a low-spin S=1/2 ground state.

Mn prefers divacancy sites over substitutional sites.

Heisenberg couplings between Mn in divacancy sites are very weak.

Abstract

We use density-functional theoretical methods to examine the recent prediction, based on a mean-field solution of the Zener model, that diamond doped by Mn (with spin S=5/2) would be a dilute magnetic semiconductor that remains ferromagnetic well above room temperature. Our findings suggest this to be unlikely, for four reasons: (1) substitutional Mn in diamond has a low-spin S=1/2 ground state; (2) the substitutional site is energetically unfavorable relative to the much larger "divacancy" site; 3) Mn in the divacancy site is an acceptor, but with only hyperdeep levels, and hence the holes are likely to remain localized; (4) the calculated Heisenberg couplings between Mn in nearby divacancy sites are two orders of magnitude smaller than for substitutional Mn in germanium.