Magnetic Properties Of Ferromagnetic Thin Films On Porous Anodized Alumina

Porous anodized alumina(PAA),not only with simple making process but also with many other advantages,such as uniform distribution,high porous density,without linking between porous,and also with uniform porous direction.We can also control the sizes of the porous and it can be a good choice as a template.In recent years,the PAA template used for synthesizing nano-structure material in one-dimension is concerned.It have been studied in detailed.And this paper shows that the special magnetic properties of Fe film with PAA underlayer.The spontaneous magnetization process of Fe nano-wire is simulated with the software(OOMMF) of micro-magnetic and also the magnetization reversal process in the magnetic field.The first part of this paper is to anodize the aluminum film to form porous structure which is deposited by magnetron sputtering.The Fe films with different thicknesses were deposited on PAA.In order to compare the magnetic properties,Fe film with the same thickness was deposited on aluminum film without being anodized or on glass substrate directly.The magnetic properties of Fe film with different substrate were measured by Vibrating Sample Magnetometer(VSM).And the results were show that the substrate of PAA could enhance the coercivity of Fe film in certain thickness range when magnetic field parallel or perpendicular to the Fe film plane.It is very important in the areas of magnetic record and magnetic storage.It shows that the coercivity increases with the angle(θ) which was between the magnetic field and film plane.Whenθget a certain value,there is a maximum coercivity.After that coerciviy decrease withθincrease.So the PAA underlayer can change the direction of easy magnetic axis. It is because that the Fe film deposited on PAA copied the porous structure,and with different directions of easy magnetic axis in different position(in or out of the holes),in order to keep a minimum total energy, the Fe film get a certain magnetic direction by the magnetostatic interaction of Fe in and out of the holes.Micro-magnetic simulation was used to study the magnetic properties of Fe nanowire in the second part of this paper.The magnetization reversal mechanism was researched by simulation the magnetization process of Fe nano-wire with same length but different diameter.The results are that magnetization reversal mechanism of nano-wires depeded on the diameter intensively.Reversion mode is consistent reversal when with smaller diameter.Reversion mode transition for two different types of nuclear magnetization(the same cross-section of the magnetization of nuclear or nuclear magnetization of the vortex cross-section) of the formation and spreading.The reversal process of nanowires through the multi-domain vortex centers move to achieve when the diameter is bigger.The coercivity of nano-wire with different diameter was calculated,explained the relationship between the coercivity change with the diameter in the view of Magnetization reversal mechanism.