Lecture

Magnetic Anisotropy: Engineering and Quantum Effects

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Description

This lecture explores the atomic-scale engineering of magnetic anisotropy in nanostructures through interfaces and interlines, discussing the effect of crystal structure on recording media, coherent vs. incoherent reversal, and the impact of particle shape. It delves into classic vs. quantum magnetic anisotropy, quantum tunneling of magnetization, level splitting induced by crystal field, phonon, and electron scattering, and quantum tunneling of magnetization in Mn12-acetate. The lecture also covers the superlattice of single atom magnets and provides an overview of mesoscopic physics, from macroscopic to nanoscopic scales, including the behavior of magnetic moments in different domains.

Official source

Ontological neighbourhood

Physics

Condensed matter physics: Phase transitions

Related concepts (26)

Magnetic domain

A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. When cooled below a temperature called the Curie temperature, the magnetization of a piece of ferromagnetic material spontaneously divides into many small regions called magnetic domains. The magnetization within each domain points in a uniform direction, but the magnetization of different domains may point in different directions.

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.

Magnetic anisotropy

In condensed matter physics, magnetic anisotropy describes how an object's magnetic properties can be different depending on direction. In the simplest case, there is no preferential direction for an object's magnetic moment. It will respond to an applied magnetic field in the same way, regardless of which direction the field is applied. This is known as magnetic isotropy. In contrast, magnetically anisotropic materials will be easier or harder to magnetize depending on which way the object is rotated.

Magnetic moment

In electromagnetism, the magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include loops of electric current (such as electromagnets), permanent magnets, elementary particles (such as electrons), composite particles (such as protons and neutrons), various molecules, and many astronomical objects (such as many planets, some moons, stars, etc).

Magnetocrystalline anisotropy

In physics, a ferromagnetic material is said to have magnetocrystalline anisotropy if it takes more energy to magnetize it in certain directions than in others. These directions are usually related to the principal axes of its crystal lattice. It is a special case of magnetic anisotropy. In other words, the excess energy required to magnetize a specimen in a particular direction over that required to magnetize it along the easy direction is called crystalline anisotropy energy.

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