Investigation of gamma-Fe4N-GaN Nanocomposites: Structural and Magnetic Characterization, Mössbauer Spectroscopy and Ab-initio Calculations

SAJITH KURIAN; SAYAN BHATTACHARYYA; JUDITH DESIMONI; EITEL L. PELTZER Y BLANCÁ; ARLES V. GIL REBAZA; N.S. GAJBHIYE

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Año: 2010 vol. 114 p. 17542 - 17548

1932-7447

A controlled one step ammonolysis method with three different Fe:Ga ratios(70:30, 50:50 and 30:70) was used to synthesize functional nanocomposite materialconsisting of 30-40 nm particles of γ´-Fe4N, Fe4-xGaxN phases in a GaN and Fe-dopedGaN phase matrix. The γ´-Fe4N, Fe4-xGaxN, GaN phases were confirmed by the Rietveldanalysis of the X-ray diffraction patterns, while Fe-doped GaN phase was confirmed from Mössbauer spectroscopy and magnetization measurements. The magnetization of the superparamagnetic nanoparticles was expectedly reduced with the Ga incorporation in the samples. The coexistence of antiferromagnetic Fe4-xGaxN and the ferromagnetic γ´-Fe4N phases resulted in an exchange bias effect (hysteresis loop shift of 28 Oe at 5 K), and a gradual magnetic phase transition from 250 K down to 55 K. Mössbauer spectroscopic showed a hyperfine magnetic field distribution that, the Ab-initio calculations duly supported. Ab-initio calculations of the equilibrium lattice and hyperfine Mössbauer parameters were also performed.