If you place a neodymium magnet on one side of a 1/8-inch thick steel sheet, will the other side of the steel sheet attract metal?

What is happening when the magnet touches steel?

When you put a strong neodymium magnet against a steel sheet, the steel becomes part of the magnetic circuit. Steel has high magnetic permeability, so it provides an easy path for magnetic flux. That flux magnetizes the steel, creating a north and south polarity pattern in the sheet.

Why the other side can become magnetic

Magnetization in a ferromagnetic material is not confined to the surface. Domains inside the steel align with the applied magnetic field, so the sheet develops a magnetic field that reaches the far face. An object placed on the far face can be attracted because it completes the flux path.

Why the attraction is weaker through 1/8 inch

The field outside a magnet drops quickly with distance. With a thickness of $1/8\text{ in} \approx 3.2\text{ mm}$, the far side is effectively “3.2 mm away,” plus any air gap from paint, scale, or imperfect contact. Also, a large steel sheet can carry much of the flux within itself, which reduces how much “leaks out” into the air on the far side to grab another object.

What changes the result in practice

• Magnet strength and size: larger/thicker neodymium magnets send more flux through the sheet.
• Steel type and thickness: mild low-carbon steel magnetizes well; thicker steel generally reduces the far-side field.
• Saturation: if the steel near the magnet approaches saturation (around $1\text{ to }2\ \text{T}$ depending on alloy), it cannot carry much more flux, which limits gains.
• Air gaps: even a small gap greatly reduces pull on the far side.

Quick rule of thumb

You should expect some attraction on the opposite face for ferromagnetic items, but do not expect it to feel like the magnet itself unless the magnet is large and the sheet is thin and in tight contact.