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Evolution of Magnetic and Chemical Order on Nano- Scale in Hf-Fe Metallic Glasses

Static and dynamic magnetic behaviour of Hf100−xFex (20 ≤ x ≤ 90) metallic glasses in the temperature range 1.5–300 K and magnetic fields up to 5.5 T reveal some important conclusions about the chemical order. For 25 ≤ x ≤ 43 the magnetic susceptibility increases rapidly with x due to the onset of magnetic correlations in the vicinity of the transition into the ferromagnetic state, xc~50. However, for 35 ≤ x ≤ 43 the alloys consist of self-assembled magnetic nanoclusters embedded within a paramagnetic matrix. This was concluded after study of the slow dynamics of magnetization and characteristic behaviour of ac- susceptibility, which were explained with the thermal activation of magnetic moments of the nano-clusters over the anisotropy barriers. These clusters grow rapidly with increasing x. In this way, magnetic method showed as very convenient in indicating the evolution of chemical order on nanometer scale. Altogether, Hf–Fe glassy alloys evolve from the superconducting and paramagnetic through the superparamagnetic to the ferromagnetic state with increasing iron content. This might be of relevance for other systems with the non-trivial magnetic behaviour.

alloys; metallic glasses; magnetization; nanometre sized clusters; thermal activation of magentic moments

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