12 Magnetic Properties of Materials 12.1·Fundamentals Modern technology would be unthinkable without magnetic ma- terials and magnetic phenomena.Magnetic tapes or disks(for computers,video recorders,etc.)motors,generators,telephones, transformers,permanent magnets,electromagnets,loudspeak- ers,and magnetic strips on credit cards are only a few examples of their applications.To a certain degree,magnetism and elec- tric phenomena can be considered to be siblings since many com- mon mechanisms exist such as dipoles,attraction,repulsion, spontaneous or forced alignment of dipoles,field lines,field strengths,etc.Thus,the governing equations often have the same form.Actually,electrical and magnetic phenomena are linked by the famous Maxwell equations,which were mentioned already in Chapter 10. At least five different kinds of magnetic materials exist.They have been termed para-,dia-,ferro-,ferri-,and antiferromagnet- ics.A qualitative as well as a quantitative distinction between these types can be achieved in a relatively simple way by utiliz- ing a method proposed by Faraday.The magnetic material to be investigated is suspended from one of the arms of a sensitive bal- ance and is allowed to reach into an inhomogeneous magnetic field(Figure 12.1).Diamagnetic materials are expelled from this field,whereas para-,ferro-,antiferro-,and ferrimagnetics are at- tracted in different degrees.It has been found empirically that the apparent loss or gain in mass,that is,the force,F,on the sample exerted by the magnetic field,is: FVxH盟 (12.1)12 Modern technology would be unthinkable without magnetic ma￾terials and magnetic phenomena. Magnetic tapes or disks (for computers, video recorders, etc.) motors, generators, telephones, transformers, permanent magnets, electromagnets, loudspeak￾ers, and magnetic strips on credit cards are only a few examples of their applications. To a certain degree, magnetism and elec￾tric phenomena can be considered to be siblings since many com￾mon mechanisms exist such as dipoles, attraction, repulsion, spontaneous or forced alignment of dipoles, field lines, field strengths, etc. Thus, the governing equations often have the same form. Actually, electrical and magnetic phenomena are linked by the famous Maxwell equations, which were mentioned already in Chapter 10. At least five different kinds of magnetic materials exist. They have been termed para-, dia-, ferro-, ferri-, and antiferromagnet￾ics. A qualitative as well as a quantitative distinction between these types can be achieved in a relatively simple way by utiliz￾ing a method proposed by Faraday. The magnetic material to be investigated is suspended from one of the arms of a sensitive bal￾ance and is allowed to reach into an inhomogeneous magnetic field (Figure 12.1). Diamagnetic materials are expelled from this field, whereas para-, ferro-, antiferro-, and ferrimagnetics are at￾tracted in different degrees. It has been found empirically that the apparent loss or gain in mass, that is, the force, F, on the sample exerted by the magnetic field, is: F
V $ 0 H d d H x , (12.1) Magnetic Properties of Materials 12.1 • Fundamentals