A tunnel magnetic resistance element includes the following, a fixed magnetic layer with a fixed direction of magnetization, a free magnetic layer in which the direction of magnetization changes, and an insulating layer which is positioned between the fixed magnetic layer and the free magnetic layer. The fixed magnetic layer, the free magnetic layer, and the insulating layer form a magnetic tunnel junction. A resistance of the insulating layer changes by a tunnel effect according to a difference in an angle between the direction of magnetization of the fixed magnetic layer and the direction of magnetization of the free magnetic layer. The free magnetic layer includes a ferromagnetic layer, a soft magnetic layer, and a magnetic bonding layer placed in between. Material of the magnetic bonding layer include Ru or Ta, and a layer thickness is 1.0 nm to 1.3 nm.

A magnetic film includes iron and copper distributed between opposing first and second major surfaces of the magnetic film. The copper has a first atomic concentration C1 at a first depth d1 from the first major surface and a peak second atomic concentration C2 at a second depth d2 from the first major surface, d2>d1, C2/C15.

A perforating gun includes a charge tube having shaped charges affixed thereto. Each shaped charge includes a radially outward pointing post adapted to receive a detonator cord. A retention member installed on the post provides a compressive force that energetically couples the detonator cord to the post. The radially outermost portion of the retention member is radially flush with or radially recessed relative to the radially outermost portion of each post. In one embodiment, the retention member has a rounded medial portion, a central opening and a pair of locking tabs that point radially inward to the central opening. Each post may include a slot for receiving the detonator cord and a circumferential groove that is adapted to receive the locking tabs.

A magnetic film includes iron and copper distributed between opposing first and second major surfaces of the magnetic film. The copper has a first atomic concentration C1 at a first depth d1 from the first major surface and a peak second atomic concentration C2 at a second depth d2 from the first major surface, d2>d1, C2/C15.