The Preparation And Magnetic Properties Studies Of Ordered Magnetic Nanowire Aarrays

In this thesis, ordered magnetic nanowire arrays were fabricated and studied. Theoretically, number simulation was conducted to figure out the magnetic properties and the mechanism of magnetization process. The contents were summarized as following:Firstly, ordered porous Anodic Aluminum Oxide (AAO) template was prepared by two-step anodization method. The results from atom force microscope (AFM) and scanning electron microscope indicated that our home-made AAO templates have uniformed diameters and interpore distances. The AAO template was very suitable to fabricate 1 D (one dimension) nanostructure materials.Secondly, ordered magnetic nanowire arrays were deposited into AAO by alternating current electrodeposition (AC electrodeposition). Emphasis was imposed on the relations between coercivities field and different magnetic field orientations as well as nanowire diameters at room temperature. The measured coercivity as a function of angle (θ) between the field and wire axis revealed that the coercivity decreased with increasing the value ofθfor various Cobalt nanowires electrodeposited into AAO template. Although the coercivity decreased with increasing the nanowire diameter, all the Co nanowire displayed evident perpendicular magnetic anisotropy, with its easy axis along the nanowire. The point was ascribed to the natural shape anisotropy of nanowire. In addition, all the Co nanowires shared the characteristics of large coercivities and high squareness ratio, which revealed that the naonwire arrays have potential application on ultrahigh density magnetic recording.Then, with the introduction of ultrasonic vibrating technique into the pretreatment of AAO template, the iron and nickel alloy nanostructure materials were electrolessly plated in AAO templates. Vibrating sample magnetometer (VSM) tests indicated the alloys also displayed evident perpendicular magnetic anisotropy, with its easy axis parallel to the nanowire. What's more, the longer the plating time extended, the more the perpendicular anisotropy was. The independence of coercivities with external field orientation was due to the amorphous structure of as-deposit alloy.At last, based on Monte Carlo simulation, we investigated the magnetization reversal modes of the Co nanowire. The hysteresis loops and, so the angle dependence of coercivity were obtained by three models, e.g. coherent rotation, with and without the consideration of magnetocrystalline anisotropy. Comparing the simulated with the experimental results, it was found that the magnetocrystalline anisotropy played an important role on the magnetic properties of Co nanowires, and the magnetization reversal process in the Co nanowires could not easily be understood by the classical coherent rotation mode. Magnetization reversal configurations revealed that the magnetization reversal in Co nanowires with small angles was nucleation-propagation process, while in large angles it was similar to coherent rotation.