1. 4/30/2019 5:17:52 PM ferromagnetism by ibrar ahmad bs physics awkum 4/28/2019 2:27:54 AM.

2. 4/30/2019 5:17:52 PM Ferromagnetism ferromagnetism: Ferromagnetic materials have following properties: 1.In ferromagnetic materials, the magnetic lines of forces due to the applied magnetic field are strongly attracted towards the material. 2.All ferromagnetic materials become paramagnetic above a temperature called Curie temperature Tc Curie temperature Tc for iron is 707c above this temperture the iron is paramagnetic. 3.Permeability is greater than 1. comes from the term ‘ferrous’ meaning iron, the first type of metal discovered to exhibit attraction to magnetic fields.it is occure in materials in which the atoms have permenentmagnetic diapoles moments like paramagnetism. main difference : but the main difference is ferromagnetic material there is a strong interaction between nieghborin atoms thats keeps their diapole moments aligned when the external magnetic field is removed. Paramagnetism refers to materials like aluminum or platinum which become magnetized in a magnetic field but their magnetism disappears when the field is removed.

3. 4/30/2019 5:17:52 PM cont.... 4.Magnetic susceptibility is large and positive. susceptibility is already define in diamagnetism. 5.Magnetic susceptibility decreases with the rise in temperature according to Curie's law. 6.The source of ferromagnetism is the spin of the electrons. 7.Ferromagnetic materials like Fe, Co, Ni, have incomplete inner shells. These shells can be completed by using Hund’s rule. 8.Ferromagnetism is the property of a material to be strongly attracted to a magnetic field and to become a powerful magnet. Explanation: The ferromagnetic materials have a permanent dipole moment. So they act as strong magnets. graph between temperture T and susceptibility X.

4. 4/30/2019 5:17:52 PM Example: Nickel (Ni) has 28 electrons. Draw the Electron Configuration Notation. Follow Hund’s rule in the 3d sublevel so each orbital gets one electron before one orbital has 2 electrons.   1s 2s 3s 4s 2p 3p 3d  

5. 4/30/2019 5:17:52 PM questions and answer Q1: When does a ferromagnetic material become paramagnetic material? Explanation: Curie temperature is the temperature at which the magnetic properties of a material change. When the temperature is greater than curie temperature, ferromagnetic material becomes paramagnetic material. Q2:Which of the following materials have a permanent magnetic moment? Explanation: In ferromagnetic material, there will be a large number of unequal electron spins and hence there exists an enormous amount of permanent magnetic moment. Q3:Which of the following exhibits spontaneous magnetisation? Explanation: The ferromagnetic materials exhibit magnetisation even in the absence of an external field. This property is called spontaneous magnetisation. Hence ferromagnets exhibit spontaneous magnetisation. Q4:define magnetic domain and magnetic domain wall? magnetic domain:A region in which the magnetic fields of all atoms are lined up in the same direction. or A region where tiny atomic magnets (magnetic diapole moments) reside.

6. 4/30/2019 5:17:52 PM cont.... magnetic domain wall:the boundry or an interface which separating magnetic domains when T>Tc then ferro become paramagnetic. when T<Tc then ferromagnetic. T=Tc then start from ferromagnetic to paramagnetic. spin magnetic moment and orbital magnetic moment in the presence of Bext. spin magnetic moment:can not change. orbital magnetic moment: can change by applaying external magnetic field Bext in case of ferromagnetic materials align in the direction of Bext. ibrar ahmad bs physics awkum (ahmadibrar267@gmail.com)