Two useful observations about magnetic fields for you:

1. Magnetic attraction, for permanent dipoles and for induced dipoles in polarizable materials, is based on the gradient of strength of the magnetic field, rather than the field's overall strength.

2. Magnetic fields can be essentially confined within highly permeable materials. For example, configurations like the "magnetic circuit" below can be used to generate a magnetic field using an electric coil (pink) in a convenient location and have nearly all of that field energy available in the gap in the iron yoke (yellow) at some other location, with minimal field leakage outside of the yoke.

[MovGP0, CC BY-SA 2.0 de, Link]

This is a rare case where reality is more flexible than a proposal by a fiction author :-)

Two useful observations about magnetic fields for you:

1. Magnetic attraction, for permanent dipoles and for induced dipoles in polarizable materials, is based on the gradient of strength of the magnetic field, rather than the field's overall strength.

2. Magnetic fields can be essentially confined within highly permeable materials. For example, configurations like the "magnetic circuit" below can be used to generate a magnetic field using an electric coil (pink) in a convenient location and have nearly all of that field energy available in the gap in the iron yoke (yellow) at some other location, with minimal field leakage outside of the yoke.

[MovGP0, CC BY-SA 2.0 de, Link]

This is a rare case where reality is more flexible than a proposal by a fiction author :-)