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

S. KURIAN, S. BHATTACHARYYA, J. DESIMONI, E. L. PELTZER Y BLANCÁ, A. V. GIL REBAZA, AND N. S. GAJBHIYE

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Año: 2010 vol. 114 p. 17542 - 17549

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 materials consisting of 30-40 nm particles of ƒÁŒ-Fe4N Fe4-xGaxN phases in a GaN and Fe-doped GaN phase matrix. The ƒÁŒ-Fe4N, Fe4-xGaxN, and GaN phases were confirmed by the Rietveld analysis of the X-ray diffraction patterns, and the Fe-doped GaN phase was confirmed from MoNssbauer 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 ƒÁŒ-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 to 55 K. MoNssbauer spectroscopic analysis showed a hyperfine magnetic field distribution that the ab initio calculations duly supported. Ab initio calculations of the equilibrium lattice and MoNssbauer hyperfine parameters were also performed.-40 nm particles of ƒÁŒ-Fe4N Fe4-xGaxN phases in a GaN and Fe-doped GaN phase matrix. The ƒÁŒ-Fe4N, Fe4-xGaxN, and GaN phases were confirmed by the Rietveld analysis of the X-ray diffraction patterns, and the Fe-doped GaN phase was confirmed from MoNssbauer 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 ƒÁŒ-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 to 55 K. MoNssbauer spectroscopic analysis showed a hyperfine magnetic field distribution that the ab initio calculations duly supported. Ab initio calculations of the equilibrium lattice and MoNssbauer hyperfine parameters were also performed.4-xGaxN phases in a GaN and Fe-doped GaN phase matrix. The ƒÁŒ-Fe4N, Fe4-xGaxN, and GaN phases were confirmed by the Rietveld analysis of the X-ray diffraction patterns, and the Fe-doped GaN phase was confirmed from MoNssbauer 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 ƒÁŒ-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 to 55 K. MoNssbauer spectroscopic analysis showed a hyperfine magnetic field distribution that the ab initio calculations duly supported. Ab initio calculations of the equilibrium lattice and MoNssbauer hyperfine parameters were also performed.4-xGaxN and the ferromagnetic ƒÁŒ-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 to 55 K. MoNssbauer spectroscopic analysis showed a hyperfine magnetic field distribution that the ab initio calculations duly supported. Ab initio calculations of the equilibrium lattice and MoNssbauer hyperfine parameters were also performed. Introduction ƒÁŒ-Fe4N is a well-known soft ferromagneticŒ-Fe4N is a well-known soft ferromagnetic