FERROMAGNETISM AND SPIN-GLASS IN AMORPHOUS FE-ZR ALLOYS

Magnetic properties of the amorphous Fe-Zr alloys have been investigat ed on the basis of a finite temperature theory of magnetism for amorph ous alloys with strong local environment effects. The calculated magne tic phase diagram and magnetization vs. concentration curve explain we ll those obtained from experimental data, exhibiting a spin-glass ferr omagnet transition. It is demonstrated that the spin-glass behaviour n ear the amorphous pure Fe is mainly caused by the competition between the short-range ferromagnetic interactions and long-range antiferromag netic interactions via structural disorder, while the formation of fer romagnetism with increasing Zr concentration originates in the band na rrowing at the Fe site, which is caused by a reduction in average coor dination number of Fe atom due to the difference between Fe and Zr ato mic sizes. The re-entrant spin-glass behaviour in Fe-rich amorphous al loys is shown to be realized by the thermal spin fluctuations of ampli tude of local magnetic moment.