Origin of magnetic hysteresis Magnetic hysteresis in ferromagnets is primarily explained by which mechanism(s)?

Introduction / Context:
Hysteresis loops reflect memory of prior magnetization. Understanding the microphysical origin helps engineers tailor cores for transformers, motors, and magnetic storage with desired coercivity and losses.

Given Data / Assumptions:

• Polycrystalline ferromagnets with magnetic domains.
• Presence of defects, dislocations, and grain boundaries.
• Quasi-static magnetization cycles.

Concept / Approach:

Ferromagnets divide into domains to minimize energy. Under applied H, magnetization changes via two processes: (i) domain wall motion (walls move as favorable domains grow) and (ii) rotation of magnetization within domains toward the field when walls are pinned. Energy barriers at pinning sites lead to irreversible jumps (Barkhausen effect), generating hysteresis.

Step-by-Step Solution:

Verification / Alternative check:

Barkhausen noise measurements and magneto-optical imaging confirm discrete wall jumps and rotations, matching the two-mechanism picture.

Why Other Options Are Wrong:

A or C alone is incomplete; D contradicts established micromagnetics; E misattributes the effect to a single microscopic interaction.

Common Pitfalls:

Assuming only rotation or only wall motion; ignoring the role of defects and anisotropy in pinning and coercivity.

Final Answer:

motion of domain walls and domain rotation