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Single phase GaGdN and GaGdN:Si thin films were grown by gas source molecular beam epitaxy using solid Gd, Ga, and Si sources along with a RF nitrogen plasma. SQUID magnetometry indicated room temperature ferromagnetism in both materials. Defects played a large role in the magnetic ordering of the material, as seen in a drastic reduction of magnetic signal with degrading crystallinity. Highly resistive films became conductive with the addition of Si. Magnetization of the co-doped film increased with Si content, reaching levels higher than that of the singly-doped material.

It was found that oxygen co-doping at a concentration of 10 atom % in GaMnN films grown by gas-source molecular beam epitaxy under previously determined optimal growth conditions of 3 atom % manganese and a growth temperature of 700°C, did not have an effect on the magnetic properties. Oxygen doping did, however, improve the magnetic properties of films grown under nonoptimal conditions, in accordance with the prediction of Kulatov et al. [Phys. Rev. B, 66, 45203 (2002)]. For all growth conditions examined, oxygen doping greatly decreased the electrical resistivity from highly resistive to ∼2.5 × 10 - 2 Ω-cm. Oxygen co-doping was also found to produce substantial improvement in the thermal stability of the GaMnN, allowing for retention of the room temperature ferromagnetic ordering even after annealing at temperatures up to 600°C.

Ion implantation of Cr at concentrations of 3 and 5 atom % was performed in Al x Ga 1 - x P:C (x = 0,0.24,0.38) epi layers grown by gas source molecular beam epitaxy. No second phases were detected by both X-ray diffractionand transmission electron microscopy. Ferromagnetic ordering to 300 K was observed in superconducting quantum interference device (SQUID) measurements, comparable to similar samples using Mn as the dopant. As well, calculated saturation moments are found to lower for Cr-implanted materials than Mn-implanted materials. As the Al fraction in the ternary starting material is increased, the saturation moments are found to decrease. Based upon this evidence, Cr does not appear to be an advantageous choice compared to Mn for high-temperature ferromagnetism in AlGaP.

(Ga, Mn)N layers were grown by radio-frequency plasma-assisted molecular beam epitaxy with Mn concentrations of ~5 or 50 atom %. In the material doped with 5 atom % Mn, the growth conditions were adjusted to produce second phases in one case, detectable by X-ray diffraction. Under our conditions, the dominant second phases are -related and not All three types of material (single-phase or GaMn second phases at different concentrations) exhibit 300 K hysteresis in magnetic moment vs. field (M-H) plots, but the temperature dependence of the field-cooled (FC) and zero-field cooled (ZFC) magnetization is quite different in each case. A clear difference in FC-ZFC magnetization at 300 K in the single-phase material is observed. © 2003 The Electrochemical Society. All rights reserved.

Carbon-doped (p ∼ 10 1 9 cm - 3 ) GaMnP with ∼5 atom % Mn grown by gas-source molecular beam epitaxy showed ferromagnetism to

GaMnN layers grown by molecular beam epitaxy were characterized by current-voltage, temperature-dependent resistivity, and optical absorption measurements. Transitions from the Mn acceptors to the conduction band were observed in optical absorption spectra, corresponding to an energy level of E C - 1.9 eV. Electrical measurements showed the material to be high resistivity (3.2 X 10 7 Ω cm) n-type for the 3 atom % Mn concentration, with the Fermi level controlled by defects or impurities with an activation energy of 0.1 eV. Under these conditions, the GaMnN showed the highest degree of ordering per Mn atom in magnetometry measurements.