Can we use the Halbach array configuration in an electromagnet?
Halbach array is an alternative to backiron. Backiron closes the loop leaving tiny field on the back side. Halbach closes the loop by force.
Is backiron a problem for you?
Halbach is more complicated than backiron, i.e. more expensive. In the permanent magnet case it may be created by magnetisation field shape in a single part hence it can be a useful method (refrigerator magnet). With discrete permanent magnets it is a choice between backiron and twice as many magnets. With electromagnets you are talking about twice as much copper. Take your pick. One way or the other the advantage is likely to be small.