Is this also mu-metal ?

[Externet]

Hi all.

Magnets inside hard drives are bracketed by mu metal.  Is the outside plate seen in some hard drive covers also mu metal ?   Like the greyish portion on the cover below:

The covers without an attached 'plate', are they usually made of mu metal ?

 

 

Cover alone :

[Frank]

Maybe a cheaper ferrite based on the colour/cost/mass - the darker parts?

https://en.wikipedia.org/wiki/Ferrite_core

This website forum says aluminium (aluminum) cover.

https://hardforum.com/threads/what-metal-is-a-hard-drive-made-of.787462/

 

Looks like the darker parts are probably plastic, not ferrite.

 

[swansont]

Not sure what the point of a mumetal cover would be.

[Externet]

Mu metal cover/on the cover for 'deflecting' external magnetism from entering the enclosure or affecting data ?

Some hard drives have the metal plate underneath, aligned to the platters :

 

On top cover :

 

[swansont]

7 hours ago, Externet said:

Mu metal cover/on the cover for 'deflecting' external magnetism from entering the enclosure or affecting data ?

The earth's field is paltry compared to the magnets inside. 

[Externet]

Thanks.  Fully agreed;  those  strong magnets with mu metal are permeating their own flux properly away from the platter to avoid data loss. 

I suspect any lining on the covers as pictured is more to prevent nearby speakers, other hard drives and external strong fields from harmful effects.  That is the doubt that triggers this thread;  could that material be also mu metal ?.

How to test ?  Visually, they never rust, as the mu metal behaves, and same sheen.  When applied a magnet to some covers, they are not magnetic; other covers that have a liner are magnetic only on those areas.  Could be non-magnetic stainless.

Made a clumsy video, drive at left has a metal attached to top lid (eggy contour) and attracts a magnet.  Drive at right shows no attraction.

----> https://www.dropbox.com/home?preview=P1010716.MOV

[John Cuthber]

If the question is mu-metal vs aluminium then (perhaps ironically)  you can tell them apart with a magnet

[Externet]

Metals found on many probed covers are

- aluminium and

- other metal,

The 'other' there is magnetic and non-magnetic.  (Shown on video)  The question is if the 'other' magnetic is mu metal.

Better link? ----> https://www.dropbox.com/s/rk3kiwycwbkcppn/P1010716.MOV?dl=0

 

Edited January 7, 2018 by Externet
Bad? link

[Frank]

If you slide your magnet along aluminium, you will feel slight resistance and lift from the opposing magnetic field induced.