It is a very basic question for magnetic circuit design engineers.
First, the realtive magnetic permeability of materials are as follows;
(1) Bismuth 0.99983
(2) Silver and Lead 0.99993
(3) Copper 0.999991
(4) Air 1.0000004
(5) Aluminium 1.00002
(6
I do not know what do you mean in the figure. Please describe exactly the dimensions of the permanent magnets and the magnetization directions. How strong are the magnets in terms of Br and Hc.