Difficulties:The Weiss model of a ferromagnet 3.Contents 5.1 Ferromagnetism 5.1.1 The Weiss model of a ferromagnet 5.1.2 Magnetic susceptibility 5.1.3 The effect of a magnetic field 5.1.4 Origin of the molecular field 5.2 Antiferromagnetism 5.2.1 Weiss model of an antiferromagnet 5.2.2 Magnetic susceptibility 5.2.3 The effect of a strong magnetic field 5.2.4 Types of antiferromagnetic order 5.3 Ferrimagnetism 5.4 Helical order 5.5 Spin glasses 5.6 Nuclear ordering 5.7 Measurement of magnetic order 5.7.1 Magnetization and magnetic susceptibility 5.7.2 Neutron scattering 5.7.30ther techniques 4.Teaching method Teaching:Group Discussion:Autodidacticism under the guidance of the teacher 5.Comments Carefully prepare lessons,prepare students and make preparations before class:In the teaching process,we pay attention to cultivating students'creative thinking,take students as the main body and enhance students'sense of participation:Corresponding exercises and supplementary exercises after class (5.1)Estimate the size of the molecular field,Bmf in iron in units of Tesla. Compare this with uOM,the contribution to the S-field due to the magnetization.Difficulties: The Weiss model of a ferromagnet 3. Contents 5.1 Ferromagnetism 5.1.1 The Weiss model of a ferromagnet 5.1.2 Magnetic susceptibility 5.1.3 The effect of a magnetic field 5.1.4 Origin of the molecular field 5.2 Antiferromagnetism 5.2.1 Weiss model of an antiferromagnet 5.2.2 Magnetic susceptibility 5.2.3 The effect of a strong magnetic field 5.2.4 Types of antiferromagnetic order 5.3 Ferrimagnetism 5.4 Helical order 5.5 Spin glasses 5.6 Nuclear ordering 5.7 Measurement of magnetic order 5.7.1 Magnetization and magnetic susceptibility 5.7.2 Neutron scattering 5.7.3 Other techniques 4. Teaching method Teaching; Group Discussion; Autodidacticism under the guidance of the teacher 5. Comments Carefully prepare lessons, prepare students and make preparations before class; In the teaching process, we pay attention to cultivating students' creative thinking, take students as the main body and enhance students' sense of participation; Corresponding exercises and supplementary exercises after class. Problems： (5.1) Estimate the size of the molecular field, Bmf in iron in units of Tesla. Compare this with u0M, the contribution to the S-field due to the magnetization