Lecture

Magnetic Domains and Walls

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

In course

MSE-432: Introduction to magnetic materials in modern technologies

Interactive course addressing bulk and thin-film magnetic materials that provide application-specific functionalities in different modern technologies such as e.g. wind energy harvesting, electric article surveillance, spintronics, sensing, and data storag ...

Description

This lecture covers the concept of magnetic domains and domain walls in ferromagnetic materials, explaining how they result from the interplay of uniaxial anisotropy and demagnetizing fields. The instructor discusses the formation of domain walls, energy considerations, and different domain configurations observed in various materials. The lecture also delves into the magnetostatic energy of single-domain states and the impact of domain walls on energy balance. Additionally, it explores the behavior of closure domains and the transition to bubble domains under varying magnetic fields, providing insights into the domain structure of thin films with perpendicular anisotropy.

Instructor

Dirk Grundler

Official source

Ontological neighbourhood

Physics

Condensed matter physics: Phase transitions

Related concepts (32)

Single domain (magnetic)

In magnetism, single domain refers to the state of a ferromagnet (in the broader meaning of the term that includes ferrimagnetism) in which the magnetization does not vary across the magnet. A magnetic particle that stays in a single domain state for all magnetic fields is called a single domain particle (but other definitions are possible; see below). Such particles are very small (generally below a micrometre in diameter). They are also very important in a lot of applications because they have a high coercivity.

Ferromagnetism

Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagnetic materials are familiar metals that are noticeably attracted to a magnet, a consequence of their substantial magnetic permeability. Magnetic permeability describes the induced magnetization of a material due to the presence of an external magnetic field.

Antiferromagnetism

In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism. The phenomenon of antiferromagnetism was first introduced by Lev Landau in 1933.

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.

Coercivity

Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in oersted or ampere/meter units and is denoted HC. An analogous property in electrical engineering and materials science, electric coercivity, is the ability of a ferroelectric material to withstand an external electric field without becoming depolarized.

Related lectures (64)

Materials Science of Magnetic Materials

Covers the materials science of magnetic materials, focusing on properties, concepts, and optimization for functional applications.

Applications of Hard Magnets

Explores the applications and benefits of hard magnets in modern technologies, emphasizing their compact design advantages.

Magnetic Hysteresis: Behavior and Loops

Covers magnetic hysteresis, coercive fields, and soft magnetic materials, including the history of coercive fields and interpreting hysteresis curves.

Anisotropy and Hard Magnets

Explores anisotropy, hard magnets, BHmax, and rare earth elements in magnetic materials.

Magnetic Domains and Walls: Properties and Characteristics