---
title: "Para, ferro, antiferro and ferrimagnetism"
subject: "Electrical Engineering Material"
chapter: 4
key: "semester_3/electrical_engineering_material:para-ferro-antiferro-ferri"
source: https://www.bctengineer.com/q/semester_3/electrical_engineering_material/para-ferro-antiferro-ferri
site: BCT Engineering
---

# Para, ferro, antiferro and ferrimagnetism

Electrical Engineering Material · Chapter 4: Magnetic Materials

- Asked in: 2071 Shrawan, 4 marks; 2069 Asar, 6 marks (asked 2 times)
- Video: [Ferro Magnetic | Ferri Magnetic | Anti Ferro Magnetic | Para & Dia Magnetic Properties solids(L-17)](https://www.youtube.com/watch?v=5ejySlvdDfM) — VEDANTU NEET MADE EJEE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/electrical_engineering_material/para-ferro-antiferro-ferri
- Whole chapter: https://www.bctengineer.com/md/semester_3/electrical_engineering_material/chapter-4

## Question

Based on magnetization, explain about the paramagnetism, ferromagnetism, antiferromagnetism and ferrimagnetism.

## Short answer

Paramagnetism: random moments, small positive χ. Ferromagnetism: parallel moments, large χ, domains. Antiferromagnetism: antiparallel equal moments, net zero. Ferrimagnetism: antiparallel unequal moments, net magnetization, high resistivity.

## Answer

These four classes all have atoms with permanent magnetic moments (unpaired electron spins); they differ in how the neighbouring moments interact and line up.

```text
 Paramagnetic      Ferromagnetic
  ^  /  ->  \       ^  ^  ^  ^
  v  <-  /  ^       ^  ^  ^  ^
 (random)          (parallel)

 Antiferromagnetic Ferrimagnetic
  ^  v  ^  v        ^  v  ^  v
  v  ^  v  ^        (big up, small down)
 (equal, opposite) (unequal, opposite)
```

#### Paramagnetism
- Moments do not interact, so thermal agitation keeps them random; $M = 0$ without a field.
- A field partly aligns them, giving small positive $\chi$ ($10^{-5}$–$10^{-3}$), $\mu_r$ slightly above 1.
- Curie law: $\chi = C/T$. Examples: Al, Pt, O₂, CuSO₄.

#### Ferromagnetism
- Strong positive exchange interaction makes neighbouring moments **parallel**; spontaneous magnetization in **domains**.
- Very large $\chi$ ($10^2$–$10^5$), hysteresis, saturation.
- Above Curie temperature it becomes paramagnetic: $\chi = C/(T - T_C)$. Examples: Fe, Co, Ni.

#### Antiferromagnetism
- Negative exchange interaction makes neighbouring moments **antiparallel and equal**, so net $M = 0$.
- Small positive $\chi$, which increases with $T$ up to the **Néel temperature** $T_N$, then falls: $\chi = C/(T + \theta)$ above $T_N$.
- Examples: MnO, FeO, NiO, Cr.

#### Ferrimagnetism
- Two sublattices with **antiparallel but unequal** moments; the difference gives a net spontaneous magnetization.
- Large $\chi$, domains and hysteresis like ferromagnets, but very high resistivity (ceramic), so low eddy-current loss.
- Examples: Fe₃O₄ (magnetite), MnZn and NiZn ferrites, YIG.

| Property | Para | Ferro | Antiferro | Ferri |
|---|---|---|---|---|
| Spin alignment | Random | Parallel | Antiparallel, equal | Antiparallel, unequal |
| $\chi$ | Small +ve | Very large | Small +ve | Large |
| Critical temp. | None | Curie $T_C$ | Néel $T_N$ | Curie/Néel $T_N$ |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. All four classes share:
   A. Atoms with permanent moments differing in interaction
   B. No atomic moments
   C. Negative χ
   D. Zero resistivity
   Answer: A. They differ in how moments interact. (Key point: Common feature)

2. Paramagnet susceptibility:
   A. C/(T+θ)
   B. Independent of T
   C. C/T
   D. C/(T - Tc)
   Answer: D. Moments don't interact. (Key point: Curie law)

3. In antiferromagnets χ:
   A. Rises with T up to TN then falls
   B. Falls then rises
   C. Is negative
   D. Is very large
   Answer: C. Above TN it behaves paramagnetically. (Key point: Néel temperature)

4. Net magnetization in ferrimagnets arises from:
   A. Antiparallel but unequal sublattice moments
   B. Parallel moments
   C. Random moments
   D. Equal opposing moments
   Answer: A. The difference remains. (Key point: Ferrimagnet)

## Related in Electrical Engineering Material

- [Ferro, ferri and antiferromagnetism](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Aferro-ferri-antiferro) — Electrical Engineering Material, chapter 4
- [Diamagnetism, ferromagnetism and ferrimagnetism](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Adia-ferro-ferri-magnetization) — Electrical Engineering Material, chapter 4
- [Ferromagnetism, paramagnetism and diamagnetism](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Adefine-ferro-para-dia) — Electrical Engineering Material, chapter 4
- [Hard magnets; dia, para and ferromagnetism](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Ahard-magnet-dia-para-ferro) — Electrical Engineering Material, chapter 4
- [Classification of magnetic materials by magnetization](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Aclassify-magnetic-materials) — Electrical Engineering Material, chapter 4, asked 6×