What are magnetic keepers? Name its material.

Magnetic keepers, also known as magnetic retainers or magnetic shunts, are devices used to maintain or preserve the magnetism of permanent magnets. They are typically made of a soft magnetic material that has high permeability and low coercivity. The most commonly used material for magnetic keepers is a type of soft iron or low-carbon steel. These materials are easily magnetized and demagnetized, allowing them to serve as temporary pathways for magnetic flux and prevent the permanent magnet from losing its magnetism over time.

When a magnetic keeper is placed across the poles of a permanent magnet, it forms a closed loop that allows the magnetic field lines to circulate through the keeper. This helps to reduce the magnetic leakage and prevents the magnet from self-demagnetizing or losing its magnetic strength. The keeper essentially provides a path of low reluctance for the magnetic field, minimizing the loss of magnetic flux.

It's worth noting that magnetic keepers are mainly used in situations where it is crucial to maintain the strength of permanent magnets, such as in the storage and transportation of magnets or in magnetic assemblies where precise magnetism is required.