What material can block a magnet's pull between two magnets?

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Discussion Overview

The discussion revolves around the question of whether there exists a material that can block or redirect the magnetic pull between two magnets, particularly in the context of practical applications such as shipping and motor design. Participants explore the properties of various materials, including mu-metal and superconductors, and their effects on magnetic fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that high permeability metals, like mu-metal, can block or redirect magnetic fields.
  • Others clarify that mu-metal does not attract magnets but instead traps and guides magnetic field lines.
  • A participant proposes that superconductors might be more effective, as they repel magnetic fields entirely due to the Meissner effect.
  • There is a repeated inquiry about the specific applications of mu-metal in hard drives and its interaction with magnets.
  • One participant expresses a desire to find a material that would not attract one magnet while simultaneously preventing another magnet from attracting or repelling it through a certain thickness.
  • Concerns are raised about the feasibility of finding such a material, with references to the challenges faced in designing motors that operate solely on magnetic forces without external energy sources.

Areas of Agreement / Disagreement

Participants generally agree that there is no material that can completely block magnetic fields; however, there are competing views on the effectiveness of different materials in redirecting or influencing magnetic interactions. The discussion remains unresolved regarding the existence of a material that meets the specific criteria outlined by some participants.

Contextual Notes

Participants mention limitations in the understanding of how materials interact with magnetic fields, particularly regarding the definitions of "blocking" versus "redirecting" magnetic forces. There is also uncertainty about the specific properties required for a material to meet the outlined conditions.

OrionVTOL
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Many of you have done this in your past. Two magnets, one under a table, another on top of the table, and moving the one under will cause the one on top to move.

Is there a material that, given the same thickness, will block this magnetic pull/repelling between the two magnets?

Thanks.
 
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Perhaps a more appropriate term instead of "blocking" is "re-direction"
 
So, this mu metal isn't something that magnets will attach to then. It talks about hard drives. Which part of a hard drive is this mu metal?
 
Magnets don't attach to anything that isn't magnetic (ie not iron, cobalt, nickel)
What mu-metal (and other high P materials) do is to trap and guide magnetic field lines.

It is probably used to shield the arm stepper motor from the disk surface and read head.
 
OrionVTOL said:
So, this mu metal isn't something that magnets will attach to then. It talks about hard drives. Which part of a hard drive is this mu metal?

They'll attach to it quite nicely, but (assuming the mu metal is thick enough for the magnet) little of the field will emerge from the far side, it will mostly remain inside the mu metal.

Superconductors might be more what you're thinking of. They actually do the opposite, excluding magnetic fields from their interior and repelling magnets:

http://en.wikipedia.org/wiki/Meissner_effect
 
What I would like to find is a material [material A] that a magnet [magnet A] would not be attracted to and a magnet [magnet B], on the other side of a certain thickness [no more than a cm] of this material A, would not attract or repell magnet A.
 
OrionVTOL said:
What I would like to find is a material [material A] that a magnet [magnet A] would not be attracted to and a magnet [magnet B], on the other side of a certain thickness [no more than a cm] of this material A, would not attract or repell magnet A.

The FAA has strict rules for the shipping of magnets on commercial carriers. Companies all know the have to package them with alternating polarity to cancel out the fields. pallidin is correct, there is really no material that "blocks" the fields, only redirects them.

People have been searching for such a material in their desire to produce a 'motor' using only magnets without introducing an outside energy source.
 
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