Macroscopic magnetic properties

A.P. Malozemoff, "Macroscopic Magnetic Properties of High Temperature Superconductors", in Physical Properties of High Temperature Superconductors /, ed. by D. M. Ginsberg, World Scientific, Singapore, Ch. 3, and references therein (1989). 

In the following sections, our first-principles bottom-up methodology will be described from a physical perspective (a full description on mathematical terms can be found in Ref. [7]). Then, the use of this methodology will be illustrated on the a-2-hydro nitronyl nitroxide [8] (hereafter called a-HNN), the simplest member of the nitronyl nitroxide family (R = H in Figure 1). The macroscopic magnetic properties and crystal structure of this compound are well known (its crystal structure is stored in the Cambridge Crystallographic Database [9] with refcode name TOLKEK). 

The macroscopic properties depend on the temperature (for instance, above a temperature called critical temperature all ferromagnets become paramagnets, but more complex phenomena are also possible). The dependence of the macroscopic magnetic properties with the temperature can help define the dominant magnetic character of the crystal. Consequently, one of the first objectives of any computational procedure is to study the dependence of the common macroscopic magnetic properties against temperature. 

The present book first recapitulates all the necessary mathematical background (Chapter 1). An overview of macroscopic magnetic properties is then presented (Chapter 2). Formulation of magnetic parameters and methods of their calculation are given in Chapters 3-6. A brief summary of magnetic behaviour is presented (Chapter 7). The core of the book deals with the temperature dependence of magnetic susceptibility for mononuclear complexes, dimers and exchange-coupled clusters (Chapters 8-11). 

The Danish physicist Hans Christian Oersted discovered that an electric current (i.e., moving electrons) gives rise to a magnetic force. In an atom, there are two possible sources of electron motion that can create a magnetic dipole and produce the resultant macroscopic magnetic properties of a material. Mag-... 

We shall see that the magnetic properties of a lanthanide or actinide ion in a crystal matrix can be very different from those of the free ion. The crystalline electric field, isotropic and anisotropic exchange forces and hybridization of the f electrons with itinerant electrons are the main factors which are determining the observed macroscopic magnetic properties. 

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