Evolution of Microstructure, Magnetic Properties, and Thermal Stabilities of Isotropic Alnico Ribbons

The magnetic properties of alnico alloys are highly dependent on the spinodally decomposed nanostructure. In this article, we report the fabrication of alnico nanoribbons and the effects of various heat treatments on the magnetic properties, spinodal decomposition, microstructure, and temperature stability. It is found that the spinodal decomposition occurs in a wider range of temperatures from 800 °C to 860 °C. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses of the microstructure confirmed that the nanostructure phases develop in a wide temperature range. Aspect ratio of the order of ~20 is obtained by optimizing the heat treatment conditions. Magnetic properties of H
_cj
= 815 Oe, B
_r
= 6.70 kG, and (BH)
_max
= 1.88 MGOe are obtained after simplified heat treatment. The magnetic properties of the alloys are measured at low (10 K) and at high (800 K) temperature, and it is shown by calculating temperature coefficient of remanence (α) and temperature coefficient of coercivity (β) that alnico ribbons possess extraordinary temperature stability at low and high temperatures.