A magnetic material has the following values of parameters: \( -1\le\chi\lt 0;\ 0\le\mu_{r}\lt 1 \), (where the symbols have their usual meanings)
The material is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Diamagnetic
The sign and size of the magnetic susceptibility \( \chi \) (with \( \mu_r = 1+\chi \)) identify the class of a material.
\( \text{Diamagnetic: } -1\le\chi\lt 0,\ \ 0\le\mu_r\lt 1 \)
\( \text{Paramagnetic: } 0\lt\chi\lt\varepsilon \text{ (small, positive)},\ \ 1\lt\mu_r\lt 1+\varepsilon \)
\( \text{Ferromagnetic: } \chi\gg 1,\ \ \mu_r\gg 1 \)
A negative susceptibility and \( \mu_r \) less than 1 mean that the material is magnetised opposite to the applied field and is weakly repelled by a magnet. This is diamagnetic behaviour.
Soft and hard ferromagnetic materials both have very large positive \( \chi \) (they differ only in how easily they lose their magnetisation), and paramagnetic materials have small positive \( \chi \).
NCERT (2026-27):
Magnetic Properties of Materials –
