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For understanding the behaviour of different elements the micro magnetic modelling is used. There are two types of simulators. Among them one is OOMMF method. OOMMF method is developed by mike Donahue. The values of OOMMF are observed in both 2-dimensional and 3-dimensional field. But in this problem only 2-dimensional is used because in convenient according to length in nanometers and for understanding the magnetic configuration of nanoelements.In below we had given a brief detail about iron and permalloy.we have mentioned about the working principle of OOMMF method and we have also given a detail about the samples taken. The results obtained are showed below for different path geometry.
1.1) Iron: Iron is a metallic element that can be rust in air and combines with some igneous rocks and biologically it is used in human body for transporting the oxygen inside the body. Iron is denoted as 'Fe'.It is the tenth abundant element in the universe. This element is discovered by Egyptians in 4000Bc and it is derived from Latin word 'Ferrum'.In the periodic table iron is located in groups 3-12.Atomic number of iron is 26 and the mass can be up to 7.86g/cm3. Iron is used in human body as haemoglobin molecule. Iron is less expensive, easily available metal in universe then among all elements it is useful metal. In universe iron is an abundant element because in sun and in many of stars it is available. In the earth's crust iron is a most available metal almost fourth place. The important iron ore is hematite it is obtained by reduction of carbon from the metal iron. In iron domains are formed due to the magnetization energy and these domains will be closure and iron can specify now to have the domain structure. Iron can form two, three or four domains depending upon the length of the material. In each domain there will be vertices point due to this point all domains are in equal distance. The main property of iron is crystalline anisotropy changes due to magnetisation in it. Anisotropy in iron is to be cubical sometimes due to the applied field on it. If more domains are formed in iron ore means the demagnetisation energy field will be reduced. The magnetization occurs in iron in all directions. Shape anisotropy of Iron metal would be low.
1.2) Permalloy: Permalloy is an element formed by blend of about 80% Nickel and 20% and has high magnetic permeability. Depending upon the direction of applied magnetic field and strength of the element the electrical resistivity varies. Mainly Permalloy is used to wrap around the copper wires that used in tele-communication purpose and also used in recording sensors and also in transformer laminations. It is also used in production of electrical transformers and inductors. In 1940 the bell laboratory has invented this Permalloy element by heat treatment and proposed it has more permeability than silicon. Molybdenum Permalloy is the composition of Permalloy. Permalloy have no anisotropy energy but it dependent on both exchange and demagnetization energy. As similar in iron as Bloch walls appears here Neel walls can be formed. Permalloy is obtained in various forms like permalloy thin films.Permalloy is used as Ac transformers and sensitive relays because it has large saturation induction. If there is change in electrical resistance then it leads to structural transformations when condensates are interfered. In Permalloy the resonance frequency and permeability depends up on the length of the material. When Permalloy is heated and if it consists of 5% of molybdenum in hydrogen element then supermalloy also will have high permeability.
1.3) OOMMF Model: OOMMF means object oriented micro magnet frame work. Basically micro magnetic modelling is used for observing different properties of materials.OOMMF is a functional micro magnetic code. This is a flexible program because every individual can create their own code. When a new code is written for this oommf by user then this new code can be replace with old code by individual itself that means easily the old code can be swiped with new code. The major goal of OOMMF is to develop portable software so that can any user can move it from one place to another place and this software must be used freely by any user. The aim is also to provide a micro modelling program with association tools.
The OOMMF is launched by clicking icon on screen then it opens from mm launch 220.127.116.11 window and it consists of mm Archive, mm graph, mm datatable, mm Disp, mm probed and mm solve 2d.In the mmprobed it consists of options like material parameters there we must give the sample details whether it as iron or permalloy.When we click on part geometry option there we can see part height, part thickness, part widthness and cell size these should be changed according to user usage. Then mmdisp will shows the iterations that take place for a sample. The mmdatatable will shows the values for the sample when iteration is going on they are total energy, demagnetization energy,iterations,Max angle, exchange energy, Anisotropy energy, Zeeman energy. Then mmgraph will show the graph that can be opened according to user usage. They can open two to three or many graphs can be opened according to user's usage.
2) Details of sample:
Samples using here are iron and permalloy.The values are given below
In this OOMMF the material parameters must be taken either Permalloy or iron.For these elements the part geometry will be changed. The part height, part width, thickness and cell size must be keep change until the final stable result is observed.
3) Results and discussions:
a) For Permalloy
1. For the dimensions part width (m)-40e-9, part height - 40e-9, thickness-4e-9, cell size-2e-9
From the above figure we can conclude that entire region is in diagonal so that's it is square in shape. As it is square shape the longest side will lies on the diagonal. As external field is not applied means the dipoles will be in longer axis. Then easy axis lies towards the plane.
The demagnetisation energy from the graph will starts decreases up to a point and after a certain point it starts saturating.Then exchange energy increases constantly and the anisotropy here is zero since all dipoles are rotating towards the same direction only then total energy remains constant. The exchange energy dominates here the demagnetisation energy. The total iterations taken place here is 4063.
2. for the dimensions partwidth-44e-9, part height-40e-9, thickness-4e-9, cellsize-2e-9
For the above values the easy axis lies on plane due to the sample values. As the sample obtain here is rectangular the dipoles rotates towards the longer side of the rectangle. Then dipoles are not facing diagonally as in case of square. The dipole tries to rotate to longer side of the rectangle from the diagonal. The anisotropy value is zero because the dipoles are rotating here towards the same direction. The demagnetisation energy reduces and then saturates after a certain point. Here the exchange energy dominates the demagnetisation energy. We can also conclude that the total energy here increases gradually. There is no Zeeman Effect exit because there is no external electric field is applied. Number of iterations takes here is 6183.
3. for the dimensions partwidth-46e-9, part height-40e-9, thickness-4e-9, cellsize-2e-9
The dipole here tries to rotate towards the longer side of the rectangular sample, which is the length of the sample. In the iteration figure we can observe that dipoles are pointing towards longer axis but the edges of dipoles are diverting. This could be possible when the dipoles moves from North Pole to South Pole and also it can be observed that dipoles are also diverting at certain edge of the rectangle. Zeeman Effect does not exist here because as there is no external electrical field is applied to it. The demagnetisation energy in graph goes decreasing and after a certain point it starts saturates this implies after a certain point the Permalloy cannot be demagnetized further. The anisotropy energy remains zero. Then total energy and exchange energy remains to be constant. Then exchange energy dominates the demagnetisation energy.
4. for the dimensions partwidth-56e-9, part height-40e-9, thickness-4e-9, cellsize-2e-9
From the above figures it can be conclude that the easy axis lies on the plane. The dipoles are towards the longer axis that is length of the sample. The anisotropy energy is zero but shape anisotropy acts on it because the sample depends on the shape. The total number iterations takes place here is 5646.The total energy here remains constant and exchange energy increases gradually. The demagnetized field starts reducing and after certain time it starts saturates. The Zeeman Energy does not exist here because as there is no external field is applied on it. The exchange energy dominates here the demagnetisation energy. In this sample the anisotropy is zero because here uniaxial anisotropy is constant.
5. for the dimensions partwidth-70e-9, part height-40e-9, thickness-4e-9, cellsize-2e-9
Here also the dipoles are moving towards to the longer side that is the length of the sample. And the dipoles starts diverting to the edge of the rectangle it could be possible because the dipoles move towards from North Pole to South Pole in a magnet. The easy axis here also lied on the plane of sample. The Zeeman energy is zero because as there is no external field is applied to it. Then total energy remains to be constant and the demagnetisation energy gradually reduces after a certain point and then it starts to saturate. Then exchange energy gradually increases and the anisotropy energy is zero. Then shape anisotropy acts on the sample and anisotropy is zero because uniaxial anisotropy is constant. The number of iterations takes place here is 3031.The Bloch walls plays an important role in Permalloy than Neels walls.
6. for the dimensions partwidth-94e-9, part height-40e-9, thickness-4e-9, cellsize-2e-9
Here in the above graphs we can conclude that Zeeman energy is zero because there is no external field is applied to it. Then dipoles starts moving towards to its axis which is gives the length of the sample. The Zeeman Energy does not exist because as there is no external electrical field is not applied on it. Number of iterations takes place here is 2836.The anisotropy is zero but also the shape anisotropy starts acting on the sample. Neels walls play an important role in Permalloy then Bloch walls. The demagnetisation energy reduces gradually then it starts to be in saturation and the exchange energy increases gradually. Then total energy remains constant. Then here exchange energy here dominates here the demagnetisation energy.
b) For iron
1. for the dimensions partwidth-420e-9, part height-420e-9, thickness-60e-9, cellsize-5e-9
From the above graphs we can see the formation of single vortex. Then demagnetisation energy dominates here the exchange energy. The exchange makes here the dipoles to align homogenously but the demagnetisation energy dominates here the exchange energy and forms the domain wall. The anisotropy energy is not zero as in case of permalloy.Here cubic anisotropy acts on it. Then net magnetisation energy is zero here at the centre of the domain wall. Total energy increases here gradually. Here also Zeeman energy will not exist because as there is no external field is applied to it. The total iteration takes place here is 3736.
2. for the dimensions partwidth-480e-9, part height-240e-9, thickness-60e-9, cellsize-5e-9
Here we can observe a formation of two domain walls with two vortexes this is due to formation of Bloch walls. Bloch walls are observed in this sample because to the thickness of the sample. If there is increase in thickness of sample there is a chance of formation of Neels walls rather than Bloch walls. The demagnetisation energy dominates the exchange energy. Number of iterations takes place here is 2027.The Cubic anisotropy acts on it. Zeeman Effect here is zero because as there is no electrical field is applied to it.
3. for the dimensions partwidth-540e-9, part height-240e-9, thickness-60e-9, cellsize-5e-9
We can see the different number of vortex formation in the domain structure. Demagnetisation energy here is minimum here as compared to the exchange energy. Since the length of sample increases this causes formation of two domain walls. The net magnetisation energy at the centre of two domain walls is zero. Cubic anisotropy acts on it. Total number of iteration exits here is 2568.And the Zeeman energy is zero and the total energy increases gradually.
4. for the dimensions partwidth-660e-9, part height-240e-9, thickness-60e-9, cellsize-5e-9
Here the demagnetisation energy is very high then compared to the exchange energy. Since the exchange energy makes dipoles to be aligned homogenously and the demagnetisation energy dominates the exchange energy and leads to form domain walls. Increase in the dimension of the sample tends to give us three closure domains vortices. In this structure we obtain high demagnetisation energy. Total energy increases gradually and the net magnetisation formed at the centre of domain walls is zero. The number of iterations takes place here is 6359.
5. for the dimensions partwidth-800e-9, part height-240e-9, thickness-60e-9, cellsize-5e-9
From above figures we can conclude that sample as high demagnetisation energy as compared to the exchange energy. The centre formed in this sample may be because of high exchange energy compared than to the demagnetisation energy which aligns the dipoles in a homogenous path. The net demagnetisation energy formed at the second domain wall is zero. But possible the net magnetisation at the centre of first domain wall may be a non-zero value. Cubic anisotropy acts on it. Zeeman Energy here is zero because as no electric field is applied to it.
6. for the dimensions partwidth-300e-9, part height-240e-9, thickness-60e-9, cellsize-5e-9
The number of iterations takes place here is 1741.A single vortex formed and one domain wall exist here. The dipoles makes to align by exchange energy to be homogenously but here demagnetisation energy dominates here exchange energy and leads to form domain walls.net magnetisation at the centre of domain wall may be leads to zero. As there if increase in thickness value takes place then Bloch walls are formed.
The above study was made on the magnetic properties of iron and Permalloy using the OOMMF software. As iron is a hard magnetic material and Permalloy is a soft magnetic material, the net magnetisation obtained for this samples are different. Here we had investigated on some many energies like Demagnetisation energy, Zeeman energy, and Anisotropy energy and about total energy as the results displayed in the above. In the absence of any applied magnetic field the total energy is sum of the all individual energies. The Zeeman Effect is Zero because as there is no external field is applied. Here we have observed that as there is an increase in thickness of material it can leads to from the Neels wall or Bloch wall. Hence Neels walls are found when we observe lower thickness and large wall is formed at higher thickness. The dimension of the sample plays an important role for domain wall formation in iron and dipoles rotation in both the samples. This all where illustrated in the case of iron and Permalloy shown above.