Hence explain why the concept of exchange is necessary to explain the ferromagnetism of iron.The density of Fe is 7873 kg m-3,the relative atomic mass is 55.847,the Curie temperature TC is 1043 K and each atom carries a ment of approximately 2.2uB (5.2)Generalize the Weiss model for spins S>2.Show that the magnetization M Just below TIC is given by M (10s+02(c-2 3[(S+1)2+S2]Tc and that there is a discontinuity in the heat capacity at TC equal to (25+1)2-1 ac=mk2+12+ You will need the relation Bs(y)= 「2s+1)2-11y (292 (25+1)4-11y3 (2S4 +005y1 (5 3)MnF has the body-centred position in the unit cell.Below 70 K the spins of the Mn ions become antiferromagnetically aligned along the c axis with the spins of an ion at the centre of the unit cell aligned opposite to those at the corners.The neutron scattering from a powdered sample of MnF:is measured using an incident neutron wavelength of 0.3 nm and an angle of scattering between 0 ind 90 Sketch the results you would expect to observe at (a)100 K and (b)10 K.You can neglect the scattering from the F ions. Chapter Six:Order and broken symmetry 1.Teaching aims Know the different types of magnetic ground state which can be produced by these interactions 2.Keypoints and Difficulties Keypoints:Broken symmetry:Phase transitions:Domains Difficulties:Broken symmetry:Domains 3.Contents 6.1 Broken symmetry 6.2 Models 6.2.1 Landau theory of ferromagnetism Hence explain why the concept of exchange is necessary to explain the ferromagnetism of iron. The density of Fe is 7873 kg m-3, the relative atomic mass is 55.847, the Curie temperature TC is 1043 K and each atom carries a moment of approximately 2.2uB . (5.2) Generalize the Weiss model for spins S > 2. Show that the magnetization M just below TC is given by and that there is a discontinuity in the heat capacity at TC equal to You will need the relation (5.3) MnF2 has a tetragonal crystal structure in which the Mn ions are situated at the corners of the tetragonal unit cell a = b =0.5 nm and c =0.3 nm, and at the body-centred position in the unit cell. Below 70 K the spins of the Mn ions become antiferromagnetically aligned along the c axis with the spins of an ion at the centre of the unit cell aligned opposite to those at the corners. The neutron scattering from a powdered sample of MnF2 is measured using an incident neutron wavelength of 0.3 nm and an angle of scattering between 0° and 90°. Sketch the results you would expect to observe at (a) 100 K and (b) 10 K. You can neglect the scattering from the F ions. Chapter Six: Order and broken symmetry 1. Teaching aims Know the different types of magnetic ground state which can be produced by these interactions 2. Keypoints and Difficulties Keypoints: Broken symmetry; Phase transitions; Domains Difficulties: Broken symmetry; Domains 3. Contents 6.1 Broken symmetry 6.2 Models 6.2.1 Landau theory of ferromagnetism