An example of a ferromagnetic oxide is

Options

A. `CrO_2`
B. `TiO_2`
C. `Fe_3O_4`
D. `Mn_2O_7`

Answer

To solve the question regarding an example of a ferromagnetic oxide, we can follow these steps:

### Step 1: Understand Ferromagnetic Oxides
Ferromagnetic oxides are materials that exhibit ferromagnetism, meaning they can be magnetized and retain their magnetic properties even after the external magnetic field is removed.

### Step 2: Identify Common Ferromagnetic Oxides
Some common examples of ferromagnetic oxides include:
- Magnetite (Fe3O4)
- Hematite (Fe2O3)
- Chromium dioxide (CrO2)

### Step 3: Focus on the Given Options
In the context of the question, we need to identify which of the mentioned oxides is a ferromagnetic oxide. The video transcript specifically mentions CrO2 as a ferromagnetic oxide.

### Step 4: Confirm the Properties of CrO2
- **Chemical Formula**: CrO2
- **Structure**: CrO2 crystallizes in a rutile structure.
- **Curie Temperature**: The Curie temperature of CrO2 is approximately 392 K, which is the temperature above which it loses its ferromagnetic properties.

### Step 5: Final Answer
Based on the information provided, the example of a ferromagnetic oxide is **CrO2**.