Carmine Vittoria, Northewestern University, DMR 0400676

1. Deposition of hexagonal ferrites by the ATLAD technique - gateway to new and exotic ferrite materials Carmine Vittoria, Northewestern University, DMR 0400676 Hexagonal ferrites are a technologically important member of the ferromagnetic oxides family that finds applications in electronic devices, computers and data storage systems, medical and non-destructive evaluation sensors, satellite and wireless communication systems, etc. With the emphasis on device miniaturization in modern technologies much effort has been dedicated in recent years to the growth of high quality hexagonal ferrites in epitaxial thin film form. Laser ablation deposition has emerged as one of the most effective ferrite growth technique due to its ability to produce thin films with structural, magnetic, and microwave properties approaching those of single crystal ferrite materials. The electric and magnetic properties of hexagonal ferrites that make these materials vital in numerous applications are highly dependent on the distribution of various ions within the crystal structure. Therefore, the ability to control the ionic distribution within the crystal structure provides unique opportunities to optimize the properties of these materials towards specific applications and develop new materials that may impact future technologies. To this end, a novel and highly versatile technique has been developed by Prof. Carmine Vittoria and doctoral students Anton Geiler and Yongxue He to allow control over the ionic distribution of high quality hexagonal ferrite thin films. The technique, titled Alternating Target Laser Ablation Deposition or ATLAD, utilizes multiple ablation targets of different chemical compositions in the process of film growth. By varying the number of laser shots from each target and the order in which they occur, the crystal structure of the deposited material is grown at the atomic scale. As a result, by separating the sources of different species of ions, the technique allows control over the placement of these ions within the unit cell of the hexagonal crystal structure. Other epitaxial thin film growth techniques in use today do not possess such ability.

2. Deposition of hexagonal ferrites by the ATLAD technique - gateway to new and exotic ferrite materials Carmine Vittoria, Northewestern University, DMR 0400676 A simplified system diagram of the ATLAD technique is depicted in figure 1. Iron oxide (Fe2O3) and barium monoferrite (BaFe2O4) targets were utilized in this case to grow high quality hexagonal M-type barium ferrite (BaFe12O19) thin films on sapphire (Al2O3) substrates. Resulting films were found to possess crystallographic, magnetic and microwave properties very similar to those of single crystal M-type barium ferrite produced by other much more costly techniques. Similar films could one day be utilized in high frequency radar, global positioning, or satellite communications systems. The versatility of the ATLAD technique allowed various substitution ions, such as manganese or indium, to be introduced into the hexagonal crystal structure in a controlled fashion. Such substitutions were previously shown to affect the magnetic properties of hexagonal ferrites, such as the saturation magnetization and uniaxial anisotropy field, thereby expanding the range of possible applications. Considering the impact ferrite materials have had on numerous modern day technologies it is expected that the new generation of hexagonal ferrites made possible by the cost effective ATLAD technique will be important in future research and development efforts since these materials will possess electric, magnetic, and microwave properties different from those of present day materials.

3. Deposition of hexagonal ferrites by the ATLAD technique - gateway to new and exotic ferrite materials Carmine Vittoria, Northewestern University, DMR 0400676