Transition of fluctuation-modifying to bond-modifying Invar effect in amorphous alloys

The Invar effect, characteristic to Fe65Ni35 ordered fcc solid solution, was observed also in the case of ferromagnetic bulk metallic glasses (BMGs). While its origin is still a matter of debate, existing explanations for crystalline materials are built on the fcc lattice. However, this approach cannot be used to describe the Invar effect observed in BMGs, because they lack the crystalline structure. There are two types of Invar effects in BMGs. They are distinguished macroscopically by the range over which the magnetic interactions reduce the CTE but there is no understanding about the underlying physics. By studying the disordered atomic arrangements at multiple absorption edges the structure can be modeled. The proposed experiment will put into evidence which atomic arrangements drive the anomalous thermal expansion and improve on the understanding of magnetic phenomena in amorphous materials.