Influence of Gd Ion Substitution on the Structure and Magnetic Properties of Pulsed Laser–Deposited SrM Hexaferrite Films

ABSTRACT

In this work, the influence of gadolinium (Gd) doping on the magnetic and structural properties of strontium M‐type hexaferrite films fabricated using pulsed laser deposition (PLD) was systematically investigated. High crystal quality films of ∼820 nm thickness, with x  = 0–0.3, were grown on c ‐plane sapphire (0 0 0 1) substrates using an excimer laser with a KrF working gas that provided intense monochromatic 248 nm laser pulses. The fluence of the laser was tailored in pursuit of improving magnetic properties, such as remanence magnetization , saturation magnetization and coercivity ) of the resulting films. X‐ray diffraction confirmed high phase purity and a high degree of c ‐axis alignment normal to the film surface for compositions x  = 0, 0.1, and 0.2. Hysteresis loops, as M – H curves, showed that as the Gd concentration increased, values initially increased from 2789 G ( x  = 0) to 4246 G ( x  = 0.1), which is attributed to the presence of a secondary phase, then subsequently decreased to 1387 G ( x  = 0.3), attributed to a decrease in the M‐type phase and the corresponding increase in an secondary phase, which is antiferromagnetic at room temperature. Additionally, transmission electron microscopy (TEM) showed that at a higher concentration of Gd ( x  = 0.3), a deterioration of long‐range ordering of the M‐type crystalline phase was replaced by a short‐range order structure, either nanostructured or amorphous in nature. Values of increased from 892 G at x  = 0, to a maximum at 2029 G at x  = 0.1. A maximum value of 29 Oe was obtained at x  = 0.2. These studies were motivated by the growing need for W‐band passive control devices, that is, circulators/isolators, to meet the growing demands of both military and commercial sectors in communications and sensing and seeking. The results presented here define a path forward for the development of self‐biased miniaturized transmit/receive components required to meet these needs.