Neighbouring moments in an antiferromagnet are:

Antiparallel and equal, so net magnetization is zero

Parallel, giving large magnetization

Random with no exchange interaction

What is the sign of the exchange interaction in ferro and antiferromagnetic materials?

Positive in ferro, negative in antiferro

Negative in ferro, positive in antiferro

What are the critical temperatures of ferro and antiferromagnetic materials called?

Curie temperature Tc and Néel temperature TN respectively

Néel for ferro, Curie for antiferro

Both are called Curie temperature only

Which pair is correct?

Ferro: Fe, with domains and hysteresis; Antiferro: MnO, with no domains or hysteresis

Both show hysteresis; examples Fe and Co

Ferro: no hysteresis; Antiferro: hysteresis

2076 Chaitra · 4+1 marks

Ferromagnetic versus antiferromagnetic materials

Short answer

Ferromagnetic materials have parallel neighbouring moments, large net magnetization, high susceptibility, and exhibit hysteresis below Curie temperature; example: iron. Antiferromagnetic materials have antiparallel equal moments with zero net magnetization, small susceptibility, and a Néel temperature above which paramagnetic; example: MnO.

Distinguish between ferromagnetic and anti-ferromagnetic materials. Give an example for each class of material.

Point	Ferromagnetic	Antiferromagnetic
Spin arrangement	Neighbouring moments parallel	Neighbouring moments antiparallel, equal
Exchange interaction	Positive	Negative
Net spontaneous magnetization	Large	Zero
Susceptibility $\chi$	Very large ( $10^2$ – $10^5$ )	Small, positive
Critical temperature	Curie temperature $T_C$	Néel temperature $T_N$
Above critical temp.	$\chi = C/(T - T_C)$	$\chi = C/(T + \theta)$
Below critical temp.	$\chi$ very large, falls with $T$	$\chi$ increases with $T$ up to $T_N$
Domains and hysteresis	Present	Absent

 Ferro:      ^  ^  ^  ^  ^
 Antiferro:  ^  v  ^  v  ^

Examples

Ferromagnetic: iron (Fe), also Co, Ni.
Antiferromagnetic: manganese oxide (MnO), also FeO, NiO, Cr.

✓ Answer checked by Claude Opus 5.5 (high effort)

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Ferromagnetic versus antiferromagnetic materials

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