Annealing Effect in Amorphous Fe-Co-B-Si-Nb According to Fe/Co Ratio

Abstract

These days, electric motor qualities and energy-saving problems are significant to our society. The critical component of these problems is related to magnetic materials. In this respect, here, we investigated the (FexCo1−x)72B19.2Si4.8Nb4 (0 ≤ x ≤ 1, at 0.1 intervals) ribbon alloys’ structural, thermal, and magnetic properties. Replacing Co with Fe turned out to increase saturation magnetization up to 127.7 emu/g and improve thermal stability. Also, we conducted heat treatment at 843, 893, and 943 K for 10 mins, and the annealing effect in the amorphous (FexCo1−x)72B19.2Si4.8Nb4 (0.4 ≤ x ≤ 0.9, at 0.1 intervals) ribbons on structural and magnetic properties are analyzed. The saturated magnetization (Ms) value has increased by about 20 to 30 emu/g by the heat treatment and tends to increase as the annealing temperature increases until the annealing temperature approaches 893 K. After annealing at 943 K for 10 mins, the highest saturation magnetization of 156.8 emu/g was achieved. In addition, all four samples show the same coercivity trend. The coercivity decreases when the initial heat treatment at 843 K is applied to the ribbons. However, after annealing at this high temperature, such as 893, 943 K, the Fe3B, and (Fe, Co)23B6 phases are also generated and cancel out the good soft magnetic properties of α-(Fe, Co) phase.

Microstructure Features and Mechanical Properties of Casted CoFeB Alloy Target

“…However, the basic storage unit of STT-MRAM is the magnetic tunnel junction (MTJ), which consists of a free layer, a tunnel gate, and a fixed layer [15]. CoFeB films exhibit excellent magnetic and electrical properties due to their amorphous structure and high spin polarization, and are widely used as free and pinned layers in STT-MRAM [16][17][18][19][20]. Currently, physical vapor deposition, especially magnetron sputtering, is commonly used to prepare MTJ thin film structures by setting a strong magnetic field on the backside of the CoFeB alloy target and increasing argon ionization to continuously bombard the target atoms to deposit thin films.…”