How do the hysteresis loops of soft and hard materials compare?

Soft: narrow and steep; hard: wide and fat

Typical coercivity values:

Soft: below about 10^3 A/m; hard: above about 10^4 A/m

Soft: above 10^4; hard: below 10^3

Why is it hard to demagnetize hard materials?

Domain walls are pinned by defects and fine particles

Which pairing is right?

Soft: transformer cores and relays; hard: permanent magnets and loudspeakers

2069 Chaitra · 6 marks

Hard vs soft magnetic materials by hysteresis

Short answer

Soft materials have a narrow, steep loop with low Hc and Br, easy magnetization and demagnetization, used in AC cores. Hard materials have a wide, nearly rectangular loop with high Hc and Br, retaining magnetism, used for permanent magnets.

Differentiate soft and hard magnetic material taking help of hysteresis loop.

Magnetic materials are divided into soft and hard according to the shape of their hysteresis loop.

        B   soft                   B   hard
        ^   ___                    ^   _______
        |  / Bs                    |  /      /
     Br |-/  /                 Br  |-/      /
   -----+/--/----> H       -------+/------/----> H
       /|  / Hc small       -Hc   /|     /  Hc large
      / | /                      / |    /
     /__|/                      /__|___/
   narrow, tall loop          wide, fat loop

Point	Soft magnetic material	Hard magnetic material
Loop shape	Narrow and steep	Wide and nearly rectangular
Loop area (hysteresis loss)	Small	Large
Coercivity $H_c$	Low (< $10^3$ A/m)	High (> $10^4$ A/m)
Retentivity $B_r$	Low (remanence is easily removed)	High and stable
Permeability	High	Low
Saturation	Reached at small H	Needs large H
$(BH)_{max}$	Very small	Large
Domain wall movement	Easy (pure, annealed, large grains)	Difficult (walls pinned by defects, fine particles)
Magnetization / demagnetization	Easy	Difficult
Eddy loss	Kept low by laminations / ferrites	Not important
Examples	Soft iron, Si-steel, permalloy, soft ferrite	Alnico, NdFeB, SmCo, hard ferrite, carbon steel
Applications	Transformer, motor and generator cores, relays, electromagnets	Permanent magnets, loudspeakers, meters, PMDC motors, magnetic storage

Summary: a soft material follows the field with little loss, so it suits alternating fields; a hard material holds its magnetism, so it suits permanent magnets.

✓ Answer checked by Claude Opus 5.5 (high effort)

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