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

The structural and magnetic properties of Ho2Co17-xMnx (r = 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 Th2Zn17-type structure while the compounds with x = 0.2 are a mixture of rhombohedral Th2Zn17-type phase and a trace of the hexagonal Th2Ni17-type phase. The substitution of Mn for Co leads to a linear increase in lattice constants a, c and unit cell volume a. The Curie temperature T-C decreases linearly with increasing Mn substitution. The saturation moment firstly increases with increasing Mn substitution for x less than or equal to 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 corves 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. It, increases with increasing Mn content and K-2 is comparable to K-1 in amplitude. The magnetocrystalline anisotropy field mu H-0(A) is found first to increase and then decrease with increasing Mn concentration, attaining a maximum value of 3.7T at x = 3. (C) 2000 Elsevier Science B.V. All rights reserved.