Selective Occupancy of Fe Substitution Enhance the Room-Temperature Ferromagnetism of (Fexni1-X)2p Nanocrystals: Experimental and Theoretical Studies

Abstract

Understanding the selective occupancy of heteroatoms in phosphides is significant to regulate their properties. (FexNi1-x)2P (0 ≤ x ≤ 0.5) nanocrystals were prepared by thermal decomposition. The effects of Fe substitution on structure, morphology and magnetic properties were studied. As the Fe content increases, (FexNi1-x)2P maintain hexagonal structure with the morphologies changing from sphere to irregular sheet. The (FexNi1-x)2P nanocrystals show room-temperature ferromagnetism. The saturation magnetization (Ms) values and magnetocrystalline anisotropy are enhanced by increasing the Fe substitution. The Ms value of (Fe0.5Ni0.5)2P reaches 2.092 emu/g, 19.5 times larger than Ni2P. XPS and Mössbauer spectra show that Fe2+/Fe3+ selectively occupy tetrahedral and pyramidal positions in Ni2P, respectively, due to the difference of ionic radius, resulting in enhanced room-temperature ferromagnetism. First-principles calculations show that Fe substitution can induce ferromagnetic ordering in Ni2P, and Fe substitution in pyramidal positions induces larger magnetic moment, which further confirms the experimental results.

Keywords: (FexNi1-x)2P, Ferromagnetism, Mössbauer spectroscopy, First-principles calculations.