Which of the following statements is not ture ?

Options

A. Paramagnetic substances are weakly attracted by magnetic field
B. Ferromagnetic substances cannot be magnetised permanently
C. The domains in antiferromagnetic substances are oppositely oriented with respect to each other
D. Pairing of electrons cancels their magnetic moment in the diamagnetic substances.

Explanation

To solve the question "Which of the following statements is not true?" we will analyze each option provided in the question regarding magnetic properties of substances.

### Step-by-Step Solution:

1. **Understanding Paramagnetic Substances**:
- **Statement**: Paramagnetic substances are weakly attracted by a magnetic field.
- **Analysis**: This statement is true. Paramagnetic materials have unpaired electrons and are attracted to magnetic fields, albeit weakly.

2. **Understanding Ferromagnetic Substances**:
- **Statement**: Ferromagnetic substances cannot be magnetized permanently.
- **Analysis**: This statement is false. Ferromagnetic materials can be magnetized permanently due to the alignment of magnetic domains. Once magnetized, they retain their magnetic properties even after the external magnetic field is removed.

3. **Understanding Antiferromagnetic Substances**:
- **Statement**: The domains of antiferromagnetic substances are oppositely oriented with respect to each other.
- **Analysis**: This statement is true. In antiferromagnetic materials, the magnetic moments of adjacent atoms or ions are aligned in opposite directions, resulting in no net magnetization.

4. **Understanding Diamagnetic Substances**:
- **Statement**: Pairing of the electrons cancels their magnetic moments in diamagnetic substances.
- **Analysis**: This statement is true. In diamagnetic materials, all electrons are paired, and their magnetic moments cancel each other out, resulting in no net magnetic moment.

### Conclusion:
After analyzing all the statements, we find that the statement regarding ferromagnetic substances is not true. Therefore, the answer to the question is:

**Answer: The second statement is not true.**