Structure and magnetocrystalline anisotropy of Ho-2(Co, Si)(17) compounds

All single crystals and polycrystals of Ho2Co17-xSix compounds with Si conc entration up to x = 4 were prepared by three-are Czochralski and vacuum are melting. The structure and magnetic properties of these compounds were stu died by means of X-ray diffraction and magnetic measurements. The crystal s tructure corresponds to the hexagonal Th2Ni17 type for x = 0 and to the rho mbohedral Th2Zn17 type for 0.5 less than or equal to x less than or equal t o 3. The sample with x = 4 could not be prepared in single-phase form. The compounds with x less than or equal to 2 have their easy magnetization dire ction perpendicular to the c-axis at room temperature. The Curie temperatur e and the Co moment are strongly decreased with increasing Si concentration . The magnetic phase diagram has been constructed from the spin-reorientati on transition temperature and the Curie temperature. Based on the temperatu re dependence of the magnetization, the compensation temperatures have been determined. In the Ho2Co17 compound, the spin-reorientation transition occ urs at 1005 K, which was never reported before.