Quenching of long-range magnetic order by random interactions in amorphous alloys

Abstract

Small angle neutron scattering data on magnetically concentrated amorphous alloys have shown that the occurrence of ferromagnetic order can be suppressed by random exchange and anisotropy interactions. Two different regimes are discussed for which long-range magnetism is destroyed by random interactions: (1) alloys with large iron concentration such as Fe 91 Zr 9 and Fe 98 Tb 2 which show evidence of competing ferromagnetic and antiferromagnetic interactions which truncate the divergence of the spin correlation length, ξ . In the second class (2) are alloys for which large single-ion random anisotropy interactions destroy long range order as found in Tb 75 Fe 25 and TbFe 2 . For this case, ξ shows a cusp at T c followed by a decrease to a value near 50 Å as T→0, consistent with a dependence on the thermal averaged random anisotropy as has been developed in recent theoretical calculations.