Folks:
I’ve been trying out Kadee magnets. They work well on my cars that are properly adjusted and graphite-lubed. Most of mine are not.
I heard of the rare-earth magnet method, using 2 1/8" dia x 3/8" magnets, axially magnetized, and tried it. It worked, but it seemed a little temperamental. Too high, and the hoses snagged. Too low, and they worked great on my cars that worked well with the Kadee magnets, but not on the others.
So, since I was experimenting with NdFeB magnets on old motors (WORKED GRRRRREAT!) I also ordered some flat bar magnets, 1/8" wide x 1/16" thick x 1" long, and some that were 1/2" long, all magnetized through the 1/16" dimension. I then super glued these, flat, to the ties, in pairs, one magnet against one set of chunky Atlas spikes, the other against the opposite set. One magnet had the N pole up, the other S. The biggest challenge was keeping the magnets from grabbing each other until the glue set. Do one at a time. 
The result- fantastic! The paired magnets work just like Kadees, but with a stronger field. The .060 height is well below the railhead. They could probably be buried under the track and work fine. The only problem: I have a pair of scratchbuilt flatcars that aren’t weighted at all, except for metal wheelsets, and the magnets grab these by an air hose and lift the other end off the track. So cars will need to be weighted at least somewhat, and N scalers may experience problems.
The 1" long paired bars actually activate the delayed feature on many of my couplers, and are much less sensitive to balky couplers and above all, air hose height, than the Kadee magnets. The 1/2" long ones uncouple a car and actually hold it in place by its air hose, but don’t seem to activate the delay. THe “hold” feature could be really useful on a non-level track.
Appearance: a pair of shiny 1/8" bars. But you could add some stripwood and paint the whole mess like a pedestrian crossing or handcar turning board