A very long piece of magnetic recording tape has a length L, a width ω << L, and a thickness t << ω. The tape has a magnetization M(x) = x̂ M cos k_x.

(a) Solve Laplace’s equation for the magnetic scalar potential and calculate B(x, y, z) just above the surface of the tape. For this purpose, it is legitimate to treat the tape as both infinitely wide and infinitely long.
(b) Plot the field lines of B(r).
(c) Sketch the trajectory of a neutral atom that approaches the tape from above (but not exactly straight down). Assume that the atom’s magnetic moment m remains permanently aligned anti-parallel to B.

Transcribed Image Text:

t Z y -1- X n