`Fe_(3)O_(4)` is ferrimagnetic at room temperature but at 850K it becomes::

Options

A. diamagnetic
B. ferromagnetic
C. non-magnetic
D. paramagnetic

Answer

To solve the question regarding the magnetic properties of \( \text{Fe}_3\text{O}_4 \) at different temperatures, we can follow these steps:

### Step 1: Understand the Magnetic Properties
- **Ferrimagnetism**: This is a type of magnetism where magnetic moments of atoms on different sublattices are opposed but unequal, resulting in a net magnetic moment. \( \text{Fe}_3\text{O}_4 \) exhibits ferrimagnetism at room temperature (around 298 K).

### Step 2: Identify the Temperature Change
- The question states that \( \text{Fe}_3\text{O}_4 \) is ferrimagnetic at room temperature but asks what happens at 850 K.

### Step 3: Analyze the Effect of Temperature on Magnetic Properties
- As temperature increases, thermal energy can disrupt the alignment of magnetic domains. For ferrimagnetic materials, when heated to a sufficiently high temperature, they lose their ferrimagnetic properties.

### Step 4: Determine the New Magnetic Property
- At high temperatures (such as 850 K), ferrimagnetic materials typically transition to a paramagnetic state. In the paramagnetic state, the magnetic moments are randomly oriented due to thermal agitation, and thus the material does not exhibit a net magnetic moment.

### Conclusion
- Therefore, at 850 K, \( \text{Fe}_3\text{O}_4 \) becomes **paramagnetic**.

### Final Answer
- The answer is **D) Paramagnetic**.

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