Question

The energies involved in the process of domain growth are:
A. Exchange energy
B. Anisotropic energy
C. Domain Wall energy
D. Magnetostrictive energy
Choose the correct answer from the options given below:

• A. A, B and C only
• B. A, C and D only
• C. A, B, C and D
• D. B, C and D only

Hint:

Think of domain formation as a competition: Exchange energy wants one big domain. Magnetostatic energy wants to break it into smaller domains to reduce external fields. Anisotropy energy dictates the direction of magnetization in these domains. Domain wall energy is the "cost" of creating boundaries between them. All these factors are interlinked.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ferromagnetic materials below the Curie temperature form small regions called magnetic domains, where the magnetic moments are aligned. The formation, size, shape, and growth of these domains are governed by the minimization of the total free energy of the system, which is a sum of several energy contributions.
Step 2: Detailed Explanation:
A. Exchange energy: This is the quantum mechanical interaction that favors the parallel alignment of adjacent atomic spins. It is the fundamental origin of ferromagnetism and is responsible for the spontaneous magnetization within a domain.
B. Anisotropic energy (or Magnetocrystalline Anisotropy Energy): This energy depends on the direction of magnetization relative to the crystal lattice. Certain directions ("easy axes") are energetically favorable for magnetization. This energy influences the orientation of spins within domains.
C. Domain Wall energy: A domain wall is the transition region between adjacent domains with different magnetization directions. There is an energy cost to forming these walls, which is a combination of exchange energy (since spins are not parallel) and anisotropic energy (since spins may be oriented away from easy axes). The system tries to minimize the total wall area.
D. Magnetostrictive energy: This is the energy associated with the mechanical strain that occurs in a material when it is magnetized. The material changes its shape slightly, and this deformation stores elastic energy.
The process of domain growth, typically under an applied magnetic field, involves the movement of domain walls to expand domains aligned with the field at the expense of others. This process is driven by the minimization of the total energy, which includes all the components listed above (plus the magnetostatic energy and Zeeman energy from the external field).
Step 3: Final Answer:
All four energies—exchange, anisotropic, domain wall, and magnetostrictive—are involved in determining the magnetic domain structure and its dynamics, including domain growth.