Lecture

Magnetic Properties Overview

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In course

MSE-431: Physical chemistry of polymeric materials

The student has a basic understanding of the physical and physicochemical principles which result from the chainlike structure of synthetic macromolecules. The student can predict major characteristics of a polymer from its chemical structure and molecular ...

Description

This lecture covers the fundamental concepts of magnetization, magnetic moments, and magnetic properties of materials. It explains the induction of magnetic fields in materials, the creation of magnetic dipoles, and the distinction between diamagnetism, paramagnetism, and ferromagnetism. The instructor discusses the behavior of materials in external magnetic fields, the concept of magnetic susceptibility, and the Curie temperature effect on ferromagnetic materials.

Official source

Ontological neighbourhood

Physics

Condensed matter physics: Phase transitions

Related concepts (31)

Magnetic dipole

In electromagnetism, a magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the size of the source is reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but the analogy is not perfect. In particular, a true magnetic monopole, the magnetic analogue of an electric charge, has never been observed in nature. However, magnetic monopole quasiparticles have been observed as emergent properties of certain condensed matter systems.

Permeability (electromagnetism)

In electromagnetism, permeability is the measure of magnetization produced in a material in response to an applied magnetic field. Permeability is typically represented by the (italicized) Greek letter μ. It is the ratio of the magnetic induction to the magnetizing field as a function of the field in a material. The term was coined by William Thomson, 1st Baron Kelvin in 1872, and used alongside permittivity by Oliver Heaviside in 1885. The reciprocal of permeability is magnetic reluctivity.

Curie's law

For many paramagnetic materials, the magnetization of the material is directly proportional to an applied magnetic field, for sufficiently high temperatures and small fields. However, if the material is heated, this proportionality is reduced. For a fixed value of the field, the magnetic susceptibility is inversely proportional to temperature, that is where is the (volume) magnetic susceptibility, is the magnitude of the resulting magnetization (A/m), is the magnitude of the applied magnetic field (A/m), is absolute temperature (K), is a material-specific Curie constant (K).

Magnetic susceptibility

In electromagnetism, the magnetic susceptibility (; denoted χ, chi) is a measure of how much a material will become magnetized in an applied magnetic field. It is the ratio of magnetization M (magnetic moment per unit volume) to the applied magnetizing field intensity H. This allows a simple classification, into two categories, of most materials' responses to an applied magnetic field: an alignment with the magnetic field, χ > 0, called paramagnetism, or an alignment against the field, χ < 0, called diamagnetism.

Superdiamagnetism

Superdiamagnetism (or perfect diamagnetism) is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of magnetic permeability (i.e. a volume magnetic susceptibility = −1) and the exclusion of the interior magnetic field. Superdiamagnetism established that the superconductivity of a material was a stage of phase transition. Superconducting magnetic levitation is due to superdiamagnetism, which repels a permanent magnet which approaches the superconductor, and flux pinning, which prevents the magnet floating away.

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