Key properties of a diamagnetic material

For a diamagnetic substance:

• Magnetization is opposite to the applied field.
• Hence magnetic susceptibility is negative and very small.
• The relation is $M = \chi H$ with $\chi < 0.$
• Also, for diamagnetic substances, susceptibility is almost independent of temperature.

Identify the correct $M$ vs $H$ graph

Since $M = \chi H,$ and for diamagnetic material $\chi < 0,$ the graph of $M$ vs $H$ must be a straight line through origin with negative slope.

Among the given plots, this corresponds to graph (a).

Identify the correct $\chi$ vs $T$ graph

For diamagnetic material, susceptibility is:

• negative, and
• nearly constant with temperature.

So the $\chi$ vs $T$ graph should be a horizontal line below the temperature axis. This corresponds to graph (c).

Match with the options

Thus the correct combination for a diamagnetic material is: $\boxed{(a), (c)}$

This is Option A.

Comparison with stored answer

Stored correct answer = A.

Our derived answer also = A.

Hence, the answers agree.