Coexistence of Mn²⁺and Mn³⁺in ferromagnetic GaMnN

Abstract

Considerable efforts have been devoted recently to synthesizing diluted magnetic semiconductors having ferromagnetic properties at room temperature because of their technological impacts for spintronic devices. In 2001 successful growth of GaMnN films showing room temperature ferromagnetism and p-type conductivity was reported. The estimated Curie temperature was 940 K at 5.7% of Mn, which is the highest among diluted magnetic semiconductors ever reported. However, the electronic mechanism behind the ferromagnetic behaviour has still been controversial. Here we show experimental evidence using ferromagnetic samples that Mn atoms are substitutionally dissolved into the GaN lattice and they exhibit mixed valences of +2 (majority) and +3. The p-type carrier density decreases significantly at very low temperatures. At the same time, magnetization dramatically decreases. The results imply that the ferromagnetic coupling between Mn atoms is mediated by holes in the mid-gap Mn band.

Effect of vacancies on ferromagnetism inGaN:Mndilute magnetic semiconductors from first-principles

“…The N states remain spin unpolarized, so the total moment from the system comes only from Mn. The experimental measurement of the coexistence of an observed dominant Mn 2+ ͑d 5 ͒ and a smaller Mn 3+ ͑d 4 ͒ component in GaN: Mn has been attributed to N vacancies, 43 unlike what would be expected for simple Mn substitution for Ga.…”

The electronic structure of homogeneous ferromagnetic (Ga, Mn)N epitaxial films

“…The electronic structure of homogeneous ferromagnetic (Ga, Mn)N epitaxial films E. Piskorska-Hommel, 1,2,a) M. J. Winiarski, 1 G. Kunert, 2 I. N. Demchenko, 3 O. D. Roshchupkina, 4 J. Grenzer, 4 J. Falta, 2 D. Hommel, 2,5,6 and V. Hol y 7 1 …”

Magnetic and magnetooptical properties of ferromagnetic semiconductor GaN : Cr

“…The mag nitude of the magnetic moment changed insignifi cantly as a result of annealing, which indicates the absence of the contribution of structural defects to magnetization. The room temperature magnetization of this material reaches a considerable value of 25 G. It should be noted that such a value exceeds most of cur rently known results for GaN doped with other ele ments [3,4,[18][19][20][21], although it is not maximal [16].…”