Structure and magnetism of new rare-earth-free intermetallic compounds: Fe3+xCo3−xTi2 (0 ≤ x ≤ 3)

Balamurugan Balasubramanian,Manh Cuong Nguyen,Yaohua Liu,Shah R Valloppilly,Jie Zhang,David J Sellmyer,Xiaoshan Xu,Yunlong Jin,Cai-Zhuang Wang,Kai-Ming Ho,Bhaskar Das,Ashfia Huq,Xiaozhe Zhang

doi:10.1063/1.4968517

Abstract

We report the fabrication of a set of new rare-earth-free magnetic compounds, which form the Fe3Co3Ti2-type hexagonal structure with P-6m2 symmetry. Neutron powder diffraction shows a significant Fe/Co anti-site mixing in the Fe3Co3Ti2 structure, which has a strong effect on the magnetocrystalline anisotropy as revealed by first-principle calculations. Increasing substitution of Fe atoms for Co in the Fe3Co3Ti2 lattice leads to the formation of Fe4Co2Ti2, Fe5CoTi, and Fe6Ti2 with significantly improved permanent-magnet properties. A high magnetic anisotropy (13.0 Mergs/cm3) and saturation magnetic polarization (11.4 kG) are achieved at 10 K by altering the atomic arrangements and decreasing Fe/Co occupancy disorder.

Highlights

One focus is on new Co- and/or Fe-rich transition-metal compounds having non-cubic crystal structures, since they have potential to exhibit high magnetocrystalline anisotropy constant (K1 ≥ 10 Mergs/cm3) and saturation magnetic polarization (Js ≥ 10 kG, Js = 4πMs, Ms = saturation magnetization), both being essential for permanent-magnet applications.[6,7,8,9,10,11]
Experimentally observed values of magnetic polarization and anisotropy are only moderate from the view point of permanent-magnet applications, i.e., Js = 8.6 kG and K1 = 6.0 Mergs/cm3.12 A genetic algorithm (GA) search and subsequent first-principle calculations predict that a Fe/Co disorder has strong effects on the anisotropy of Fe3Co3Ti2
Transmission electron microscopy (TEM) measurements were carried out to investigate the microstructure of the melt-spun samples using a FEI Tecnai Osiris scanning transmission electron microscope

Summary

Introduction

Structure and magnetism of new rare-earth-free intermetallic compounds: Fe3+xCo3−xTi2 (0 ≤ x ≤ 3) We have further modified the atomic arrangements in the structure by gradually replacing Co with Fe to obtain new magnetic compounds Fe4Co2Ti2, Fe5CoTi2, and Fe6Ti2 with more promising permanent-magnet properties.

Results

Conclusion