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[...]... 2.1 SPIN AND ORBITAL STATES OF ELECTRONS In the following, it is assumed that the reader has some elementary knowledge of quantum mechanics In this section, the vector model of magnetic atoms will be briefly reviewed which may serve as reference for the more detailed description of the magnetic behavior of localized moment systems described further on Our main interest in the vector model of magnetic. .. limited 4.2 FERROMAGNETISM The total field experienced by the magnetic moments comprises the applied field H and the molecular field or Weiss field We will first investigate the effect of the presence of the Weiss field on the magnetic behavior of a ferromagnetic material above In this case, the magnetic moments are no longer ferromagnetically ordered and the system is paramagnetic Therefore, we may... here on those fundamental aspects of magnetism of the solid state that form the basis for the various applications mentioned and from which the most salient of their properties can be understood It will be clear that all these matters cannot be properly treated without a discussion of some basic features of magnetism In the first part a brief survey will therefore be given of the origin of magnetic moments,... structures have also been included in Table 4.1.1 The shortest Fe–Fe distances, for which antiferromagnetic couplings are predicted to occur according to Fig 4.1.1, are seen to adopt a wide gamut of values on either side of the Fe–Fe distance in Fe metal 22 CHAPTER 4 THE MAGNETICALLY ORDERED STATE This does not lend credence to the notion that short Fe–Fe distances favor antiferromagnetic interactions Equally... external flux density of in an external field more details about units will be discussed 14 CHAPTER 3 PARAMAGNETISM OF FREE IONS in Chapter 8) For one has J = 9/2 and g = 8/11 (see Table 2.2.1) Furthermore, we make use of the following values and At room temperature (298 K) , one derives for y in Eq (3.1.11): Since we now have shown that under the above conditions, it is justified to use only the first... direction of the field For practical reason, we will drop the subscript J and write simply m to indicate the magnetic quantum number associated with the total angular momentum This page intentionally left blank 3 Paramagnetism of Free Ions 3.1 THE BRILLOUIN FUNCTION Once we have applied the vector model and Hund’s rules to find the quantum numbers J, L, and S of the ground-state multiplet of a given type of. .. value of the magnetic moment is and its projection along the direction of the applied field is The situation is different for the spin angular momentum In this case, the associated magnetic moment is SECTION 2.2 THE VECTOR MODEL OF ATOMS 5 where is the spectroscopic splitting factor (or the g-factor for the free electron) The component in the field direction is The energy of a magnetic moment in a magnetic. .. given J the variation of the reduced magnetization M(T)/M(0) with the reduced temperature depends SECTION 4.2 FERROMAGNETISM 25 exclusively on the form of the Brillouin function It is independent of parameters that the number of partic vary from one material to the other such as the atomic moment In fact, the variation of the reduced ipating magnetic atoms N and the actual value of magnetization with... temperature dependence of each of the two sublattice moments can be obtained by means of Eq (3.1.9): with A similar expression holds for In analogy with Eq (4.2.3), it is relatively easy to derive expressions for the sublattice moments in the high-temperature limit: where The two coupled equations for and will lead to spontaneous sublattice moments for H = 0) if the determinant of the coefficients of and vanishes:... INTRODUCTION information technology without having any knowledge of the materials used for data stor age in these systems and the physical principles behind the writing and the reading of the data Special attention is therefore devoted to these subjects Although the topic Magnetic Materials is of a highly interdisciplinary nature and com bines features of crystal chemistry, metallurgy, and solid state physics, . Physics of Magnetism and Magnetic Materials This page intentionally left blank Physics of Magnetism and Magnetic Materials K. H. J. Buschow Van der. Model 156 14.4. Dependence of Soft -Magnetic Properties on Grain Size 158 14.5. Head Materials and Their Applications 159 14.5.1 High-Density Magnetic- Induction