Magnetic properties and crystallization behavior of Fe28.75Co28.75Ni17.5X8B17 (X=Si, Ge) metallic glasses

The development of Fe- and Co- based amorphous soft magnetic materials with low critical cooling rate for glass formation with a wide supercooled liquid region before crystallization has become an important topic for fundamental as technological reasons. We have synthesized new alloys with composition Fe28.75Co28.75Ni17.5X8B17 (X=Si or Ge) and we have studied the evolution of their magnetic and crystallographic properties when heated from room temperature to 900°C. The techniques used to measure their evolution are in situ powder neutron diffraction and Faraday magnetic torque. As synthesized, the alloys are vitreous with a supercooled liquid region of 48°C for the Si and Ge alloys, they are ferromagnetic with ordering temperatures of 420°C and 430°C for the Si and Ge alloys, respectively. There is a phase stability competition between the cs, BCC (α) or ccp (γ) forms as a function of the substitution scheme of the 3d transition metals (Fe, Co, Ni).