Magnetic characteristics of nanocrystalline GaMnN films deposited by reactive sputtering

The magnetic characteristics of Ga1-xMnxN nanocrystalline films (x = 0.08 and x = 0.18), grown by reactive sputtering onto amorphous silica substrates (a-SiO2), are shown. Further than the dominant paramagnetic-like behaviour, both field- and temperature-dependent magnetization curves presented some particular features indicating the presence of secondary magnetic phases. A simple and qualitative analysis based on the Brillouin function assisted the interpretation of these secondary magnetic contributions, which were tentatively attributed to antiferromagnetic and ferromagnetic phases. © 2012 Elsevier Masson SAS. All rights reserved.

Propriedades estruturais, ópticas e magnéticas de filmes de GaMnN

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Raman scattering study on vibrational modes in Ga1-xMnxN prepared by Mn-ion implantation

Raman scattering measurements have been carried out on ferromagnetic semiconductor Ga1-xMnxN prepared by Mn-ion implantation and post annealing. The Raman results obtained from the annealed and un-annealed Ga1-xMnxN demonstrate that crystalline quality has been improved in Ga1-xMnxN after annealing. Some new vibrational modes in addition to GaN-like modes are found in the Raman spectra measured from the Ga1-xMnxN where the GaN-like modes are found to be shifted in the higher frequency side than those measured from the bulk GaN. A new vibrational mode observed is assigned to MnN-like mode. Other new phonon modes observed are assigned to disorder-activated modes and Mn-related vibrational modes caused by Mn-ion implantation and post-annealing. (c) 2006 Elsevier Ltd. All rights reserved.

Magnetism and luminescence evolution due to nitrogen doping in manganese-gallium oxide nanowires

We report a new method for large-scale production of GaMnN nanowires, by annealing manganese-gallium oxide nanowires in flowing ammonia at high temperature. Microstructure analysis indicates that the GaMnN nanowires have wurtzite GaN structure without Mn precipitates or Mn-related second phases. Magnetism evolution due to nitrogen doping in manganese-gallium oxide nanowires was evaluated by magnetic measurements. Magnetic measurement reveals that the magnetization increases with the increase of nitrogen concentration. Ferromagnetic ordering exists in the GaMnN nanowires, whose Curie temperature is above room temperature. Luminescence evolution was investigated by the cathodoluminesence measurement for a single nanowire and photoluminescence measurement in a temperature range between 10 and 300 K. Experimental results indicate that optical properties can be modulated by nitrogen doping in manganese-gallium oxide nanowires. (c) 2005 Elsevier B.V. All rights reserved.

The optical absorption edge of nanocrystalline Ga(1-x)Mn(x)N films deposited by reactive sputtering

We have focused on the optical absorption edge of nanocrystalline Ga(1-x)Mn(x)N (0.00 <= x <= 0.18) films deposited by reactive RF magnetron sputtering. The films obtained are nanocrystalline with grain sizes of about 25 nm, having wurtzite structure and strong orientation texture in the c-axis direction. The optical characterizations of the absorption edges were obtained in the 190-2600 nm spectral range. The increase of the Mn content causes an increase of the absorption coefficient which can be clearly noticed at low energies, and a quasi-linear decrease of the optical gap. Broad absorption bands observed around similar to 1.3 and similar to 2.2 eV were associated with transitions between the Mn acceptor level and the valence and conduction bands, respectively. The observed changes in the optical properties due to the Mn incorporation observed in these nanocrystalline films are similar to those reported for ferromagnetic GaMnN single-crystal films.

Thermodynamic and electronic study of Ga-1 _ xMnxN films. A theoretical study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos da adição de átomos de Mn na rede do GaN via métodos de estrutura eletrônica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanocrystalline Ga1-xMnxN films grown by reactive sputtering

The growth of nanocrystalline Ga1-zMnxN (0.00 <= x <= 0.18) films grown by reactive RF-magnetron sputtering is focused here for the first time. The films were grown in a N-2 atmosphere by co-sputtering technique using a Ga target covered with small pieces of Mn onto c-GaAs (10 0), c-Si (10 0) and amorphous SiO2 substrates maintained at 500 K. Scanning electron microscopy and X-ray diffraction (XRD) experiments did not show any evidence for Mn segregation within the studied composition range. EDX measurements show that the Mn concentration is increased monotonically with the fraction of the target area covered by Mn. The XRD characterization show that the films are nanocrystalline, the crystallites having mean grain sizes in the 15-19 nm range and wurtzite structure with preferential growth orientation along the c-axis direction. The lattice parameters of alpha-GaN (a and c) increase practically linearly with the increase of Mn incorporation. The changes in the structural properties of our films due to the Mn incorporation are similar to those that occur in ferromagnetic GaMnN single-crystal films. (c) 2006 Elsevier B.V. All rights reserved.