I saw on the net another magnetic arrangement using a 2x2 bar magnet 6 inches long. 1/3 of the way in (2") and 1 inch from the edge on both sides (all 4 surfaces) tapered holes were drilled. Cone shaped coils with a small iron point attached were fitted into the holes. The holes were drilled to 1/8" from center so there was a 1/4" gap between opposing cones. A air core torroid was in the middle of the bar. A small trickle charge distorted the field. The good news about this arrangement is after drilling the holes, simply fill the holes with iron filelings and magnetise the bar. Works on exactly the same principal, I don't have a link for you will go find one. It may take a while to find it again.