Magnetic moment developed per unit volume of a material when placed in a magnetising field is known as ________ .
Answers
Explanation:
The magnetic moment is associated with the spin and orbital motion of the electron. The net (vector sum) magnetic moment of electrons in an atom/ion gives rise to the magnetic moment of the atom/ion. Quantum effects and band structure plays an important role in determining the moment of an atom or ion in a solid. This moment is measured in units of emu (erg/Oe) in cgs system, and in A.m2 in SI system. The magnetic moment due to spin only of an electron is 1 Bohr Magneton = 9.27x10-21emu =9.27x10-24 A.m2. The orbital moment in most transition metals (except Co) is quenched, and the net moment is due to electron spin. The magnetic moment of an Fe atom in metallic iron is 2.2 Bohr magnetons. To convert this into magnetization, which is the magnetic moment per gram (or magnetic moment per unit volume) we find the magnetic moment per cubic cell ( which contains 2 Fe atoms in bcc Fe metal) and divide this moment by the cell volume to obtain the magnetization in units of emu/cm3. The specific magnetization (emu/g) is obtained by dividing the above magnetization by the metal density. Fe example:
M = 2x2.2x9.27x10-21/(2.87x10-24)3 = 1725 emu/cm3
sigma = 1725/7.87 = 219 emu/g which is the specific magnetization for metallic Fe.
Fe3+ in iron oxide crystal has a moment of 5 Bohr magnetons at zero temperature (which is the sum of the moments of 5 electrons in the 3d-band) for example. The same procedure above can be used to calculate the magnetization of a collinear magnetic structure in an iron oxide or any other other magnetic material.
intensity of magnetization.........