Magnetic Properties of Fe 2GeMo 3N; An Experimental and Computational Study
A polycrystalline sample of Fe 2GeMo 3N has been synthesized by the reductive nitridation of a mixture of binary oxides in a flow of 10% dihydrogen in dinitrogen. The reaction product has been studied by magnetometry, neutron diffraction and Mössbauer spectroscopy over the temperature range 1.8 ≤ T/K ≤ 700. The electronic structure and magnetic coupling have been modelled by Density Functional Theory (DFT) and Monte Carlo methods. Fe 2GeMo 3N adopts the cubic η-carbide structure with a = 11.1630(1) Å at 300 K. The electrical resistivity was found to be ~0.9 mΩ cm over the temperature range 80 ≤ T/K ≤ 300. On cooling below 455 K the compound undergoes a transition from a paramagnetic to an antiferromagnetic state. The magnetic unit cell contains an antiferromagnetic arrangement of eight ferromagnetic Fe 4 tetrahedra; the ordered atomic magnetic moments, 1.90(4) B per Fe atom at 1.8 K, align along a <111> direction. DFT predicts an ordered moment of 1.831 B per Fe. A random phase approximation to the DFT parameterised Heisenberg model yields a Néel temperature of 549 K, whereas the value of 431 K is obtained in the classical limit for spin. Monte Carlo calculations confirm that the experimentally determined magnetic structure is the lowest-energy antiferromagnetic structure, but with a lower Néel temperature of 412 K. These results emphasise the potential of these computational methods in the search for new magnetic materials.
P. D. Battle et al., "Magnetic Properties of Fe 2GeMo 3N; An Experimental and Computational Study," Journal of Materials Chemistry, vol. 22, no. 31, pp. 15606-15613, Royal Society of Chemistry, Aug 2012.
The definitive version is available at http://dx.doi.org/10.1039/c2jm32574h
Keywords and Phrases
Antiferromagnetic State; Antiferromagnetic Structures; Antiferromagnetics; Atomic Magnetic Moment; Binary Oxides; Carbide Structure; Classical Limits; Computational Studies; Density Functional Theories (DFT); Dihydrogen; Dinitrogen; Electrical Resistivity; Fe Atoms; Heisenberg Models; Monte Carlo Calculation; Ordered Moments; Polycrystalline Samples; Random Phase Approximations; Reductive Nitridation; Ssbauer Spectroscopies; Temperature Range; Unit Cells; Antiferromagnetic Materials; Antiferromagnetism; Approximation Algorithms; Carbides; Density Functional Theory; Electric Conductivity; Electronic Structure; Magnetic Couplings; Magnetic Moments; Magnetic Properties; Molybdenum; Monte Carlo Methods; Neutron Diffraction; Paramagnetism; Neon
International Standard Serial Number (ISSN)
Article - Journal
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