Study On The Magnetic Properties Of Ferrite Nano-wires (Tubes) Prepared By Template Synthesis Method

In this paper, Co ferrite nanowires(nanotubes)/Ba ferrite nanowires were prepared by sol-gel method using porous anodic alumina oxide(AAO) membrane as template. The factors ofpreparation of the AAO,ferrite nanowires/tubes and magnetic properties were studyied by XRD,SEM,VSM methods.The factors of preparation of the AAO show:voltage on the nano-pores have a significant effect,with the oxidation voltage is increased,the pore size is even greater, nano-holes arranged more orderly,but the voltage is too high oxidation reaction would be too intense,is not conducive to the formation of nano-pore.The hole markedly improved,pore spacing significantly decreases,and the hole is more regular hexagon by two steps oxidation compared to an anodic oxidation;The oxalic acid electrolyte concentration has little effect on the anodic oxidation process in the context of a certain concentration;Appropriate opening temperature and time can be increased to extend the bore hole;With the extension of oxidation time,the membrane thickness showed"rapid growth in the first,then slowly increasing,and then smooth"changes in trends;The corrosive effec of nano-holes and barriers was intensified in high temperature,it is not conducive to the formation of AAO.The results of preparation of Co ferrite nanowires(nanotubes)showed that: deposition time and frequency that primarily affects the pore filling degree of ferrite precursor in the AAO template, thereby affecting nanowire length or formation of wires, tubes shape.Sol pH need to improve in oder to preparate longer nanowires.Co ferrite nanowire crystallinity degree increased by extension of calcining time;Higher calcination temperature not only make the cobalt ferrite nanowire crystallinity significantly increased,and part of the Al³⁺ replaces Fe³⁺,thus makes the cobalt ferrite lattice parameters decrease. Cobalt ferrite nanowires/tubes magnetic properties results show that:With the increasing of aspect ratio,cobalt ferrite nanowires saturation magnetization,residual magnetization,coercivity,squareness ratio were increased;The same diameter of cobalt ferrite magnetic properties of nanotubes is superior to a considerable diameter nanowires;calcination time and calcination temperature have significant effect on the Ms, Mr, Hc,and P of cobalt ferrite nanowires.To extend the calcining time caused by Ms,Mr, Hc,and P have increased,and higher calcination temperature makes Ms,Mr,Hc,and P both increased significantly.This is mainly due to extended time or improve the calcination temperature calcination of cobalt ferrite nanowires leading to the degree of crystallinity increased or significantly increased,and the increase of calcination temperature to make part of the Fe³⁺ has been replaced by Al³⁺,thereby increasing the ferrite magnetic properties of nanowires.The results suggest that,when the magnetic anisotropy fixed at a certain degree,the shape anisotropy of the magnetic properties of cobalt ferrite can not be ignored;Moreover,based on of Co ferrite nanowires magnetic properties have internal relations with aspect ratio,wires or tubes,morphology and crystallinity degree,we can control the magnetic properties of Co ferrite nano-wires by change the conditions of preparation of Co ferrite nano-wires.