An IM device includes a magnetic core including a base plate, a cover plate, and first, second and third magnetic columns. A straight line defined by positions of the first and second magnetic columns is parallel to a length direction, and the third magnetic column is between the first and second magnetic columns, and extends in a width direction. A first coil is wound around the first magnetic column to generate a closed magnetic flux loop, a second coil wound around the second magnetic column to generate a closed magnetic flux loop. The magnetic core includes a fourth magnetic column between the base plate and the cover plate, and close to a first terminal of the third magnetic column in the width direction. In the length direction, the fourth magnetic column overlaps with at least a portion of the first magnetic column and at least a portion of the second magnetic column.