Magnetic structure and coercivity mechanism of AlNiCo magnets studied by electron holography

Micromagnetic structure and coercivity were systematically investigated by electron holography and micromagnetic simulation. The experimental data show that the distribution of magnetic flux lines of FeCo-rich (α1) phase is different from that of AlNi-rich (α2) phase. Quantitative analysis based on the measurement of electron holography show that the magnetizations and coercivities of α1 phases for 36Co and 40Co are calculated to be 11.0 kG and 8.5 kG, 1848 Oe and 3029 Oe, respectively. Further micromagnetic simulations reveal that the decrease of α1 phase diameters and the weakened exchange coupling (increased distance) between adjacent phases are critical factors to increase the coercivities of AlNiCO magnets, well matching with the measured results from electron holography.