Magnetic properties of HoCoMn compounds with the 2:17-type structure

Abstract

The structural and magnetic properties of Ho 2Co 17− x Mn x ( x=0–4) compounds have been investigated by means of X-ray diffraction (XRD) and magnetic measurements. Powder XRD patterns show that the compounds with x=1, 3, 4 are single phase with rhombohedral Th 2Zn 17-type structure while the compounds with x=0, 2 are a mixture of rhombohedral Th 2Zn 17-type phase and a trace of the hexagonal Th 2Ni 17-type phase. The substitution of Mn for Co leads to a linear increase in lattice constants a, c and unit cell volume v. The Curie temperature T C decreases linearly with increasing Mn substitution. The saturation moment firstly increases with increasing Mn substitution for x⩽2, and then decreases. XRD measurement on magnetically aligned samples demonstrates that x=1 exhibits an easy-cone type of anisotropy at room temperature, x=2–4 exhibit an easy-axis type of anisotropy at room temperature. The spin-reorientation transitions are found in the M– T curves for all samples. The magnetic phase diagram is given. The magnetocrystalline anisotropy constants K 1 and K 2 are deduced from fitting the reversible recoil curve in the hard direction by a modified Sucksmith–Thompson plot. K 1 increases with increasing Mn content and K 2 is comparable to K 1 in amplitude. The magnetocrystalline anisotropy field μ 0 H A is found first to increase and then decrease with increasing Mn concentration, attaining a maximum value of 3.7 T at x=3.