Structure and magnetic properties of Cr-doped GaN

Abstract

Structure and magnetic properties of the Ga1−xCrxN (x=0.013, 0.063, and 0.101) have been investigated. The lattice constant of the c axis is systematically decreased with increasing Cr content. The local structure around a Cr atom maintains tetrahedral symmetry up to x=0.101 the same as the local symmetry of GaN by x-ray absorption fine structure analysis. The analysis on x=0.013 indicated that the second nearest neighbor around the absorbing Cr atoms consists of only 12Ga atoms. However, for x=0.063, the second nearest neighbor around the absorber consists of Ga and Cr atoms with an unexpectedly high ratio of about Ga:Cr=2:1. In CrK-edge x-ray absorption near edge structure, we observed the oxidation state of Cr ion increases with increasing Cr content. Ferromagnetic behavior was observed in all Ga1−xCrxN films. However, the paramagnetic component also coexists with the ferromagnetic component. Total effective magnetic moment per Cr atom decreased from 3.17μB∕atom for x=0.013 to 1.05 and 0.79μB∕atom for x=0.063 and 0.101, respectively. The decreased magnetic moments of the x=0.063 and 0.101 is possibly caused by antiferromagnetic interaction of Cr–N–Cr networks in the high Cr content samples.

Electronic structure ofGa1−xCrxNand Si-doping effects studied by photoemission and x-ray absorption spectroscopy

“…The Cr 2p spectrum of Cr 2 O 3 (Cr 3+ ) [17] is also shown for comparison. The peak position for GaCrN is close to that for Cr 2 O 3 , indicating that the valence of Cr in GaCrN is close to 3+, that is, the Cr atom is doped into GaN as a neutral impurity if Cr substitutes for Ga, consistent with the earlier reports [6,7,18] ducting GaN samples insulating [7,19]. The amount of the peak shift of each core level relative to that in GaCrN is plotted in panel (e).…”

“…The calculated moments of the Cr-rich clusters with various sizes are 0.06-1.47 µ B /Cr, corresponding well to the observed M S ∼0.25 µ B /Cr. Kim et al [7] have reported that the M S of Ga 1−x Cr x N decreases with increasing Cr concentration, which can be interpreted as due to the size increase of the antiferromagnetic Cr-rich clusters. As for Zn 1−x Co x O, for which even smaller M S has been reported, Dietl et al [25] attributed the origin of the small M S to the uncompensated moments of the Co-rich AFM nanoclusters.…”

“…X-ray absorption and photoemission studies have revealed strong hybridization between the Cr 3d states and the valence p band [4], and the formation of Cr 3d-derived states within the band gap of GaN [5,6], which suggested a high potential as an intrinsic DMS. However, high resistivity [7] and the absence of density of states at Fermi level (E F ) [5,6] have thrown doubt on the DE mechanism of the FM in Ga 1−x Cr x N. On the other hand, the substitutional transition-metal (TM)-rich clusters of nanometer sizes embedded in the host semiconductor have been observed in Zn 1−x Cr x Te [8] and suggested as another origin of ferromagnetism in DMSs [9]. Such TM-rich clusters have also been observed in other III-V-based wide-gap DMSs, Ga 1−x Mn x N [10], In 1−x Cr x N [11], and Ga 1−x Fe x N [12].…”

Correlation between morphology, chemical environment, and ferromagnetism in the intrinsic-vacancy dilute magnetic semiconductor Cr-doped Ga2Se3/Si(001)

“…The absence of a pre-edge peak in Cr K-edge spectrum demonstrates that Cr does not substitute on a tetrahedral Ga or vacancy site, as it does in Cr:GaN 33 or Cr:ZnTe, 18 and the energy of the edge is consistent with a formal valence of Cr 2+ (as in CrSe) and/or Cr 3+ (with Se neighbors screening more efficiently than oxygen). The Cr 2p absorption (Fig.…”

Effect of carbon doping on microstructure, electronic and magnetic properties of Cr:AlN films

“…[13,14], peak A in Fig. 2(a1) was due to the transition from Cr 1s electron to Al 3d-O 4p hybridized states occurring in low symmetry ligand fields such as the tetrahedral ligand field [15,16]. In the N K-edge XANES spectra (Fig.…”