The magnetic and electronic properties of Ho6Fe23−xCox (x = 0, 1, 2, 3)

Abstract

Magnetic and electronic properties of Ho6Fe23−xCox (x = 0, 1, 2, 3) compounds were investigated for the first time by experimental measurements on their polycrystalline samples combining with first-principles calculation. The samples of Ho6Fe23−xCox were successful prepared by a vacuum arc furnace. The XRD analysis and Rietveld refinement results show that Ho6Fe23−xCox crystallize in a face-centered cubic Th6Mn23-type structure with space group Fm3¯m (No.225), and their lattice parameters decrease with the increasing Co content. The M−T curves indicates that AFM-FM transition occurred at Neél temperature TN, the FM-PM transition occurred at Currie temperature TC for Ho6Fe23−xCox and the FM-PM transition belongs to a second-order transition. The Currie temperature and magnetic compensation temperature for all the samples increases with the increase of the content of Co. The maximum magnetic entropy change (-ΔSM) for the Ho6Fe23−xCox compounds under an applied magnetic field of 15 k Oe are 0.594, 1.023, 0.726 and 0.48 J kg−1 K−1 around their Currie temperature (TC = 542, 580, 622 and 654 K), respectively. This relatively large -ΔSM of Ho6Fe23−xCox occurred in a relatively high temperature region and under low applied magnetic field, pointing to the potential application as magnetic refrigeration materials using at higher temperature. The experimental results show that Co doping can regulate the magneto-thermal properties of the materials, so as to improve the magnetic entropy change of the existing magnetic refrigeration materials. The electronic properties of Ho6Fe23−xCox was studied by using the first-principle calculation. The band structures and density of states indicate that Ho6Fe23−xCox are good conductor.