Sunday, August 24, 2008
Sunday, August 17, 2008
What does "Grade N42" mean ?
The grade number of a Neodymium Supermagnet indicates how
powerfully the individual magnet is magnetized.
The units of measure of a magnet's strength are named after
Carl Friedrich Gauss, and Hans Christian Ørsted. They were
Scientists who studied magnets in the 1700's.
Ørsted's name is re-spelled Oersted because English does not
commonly use the Danish "Ø", so to make the same sound,
English uses "Oe".
The theoretical maximum for Neodymium is Grade N64
meaning 64,000,000 Gauss-Oersteds.
"Mega" is the scientific prefix for million.
So, Grade N42 would be 42 MegaGauss-Oersteds.
This is often abbreviated as "42MGOe" .
Neodymium Supermagnets cannot obtain this full strength
at normal temperatures, but can approach it at near absolute
zero temperature.
As the alloying mixtures and manufacturing processes improve,
Neodymium Supermagnets will become available in higher grades.
I have read that grade N58 has been reached in the laboratory,
and Grade N45 is available at some magnet suppliers.
Some Neodymium magnets may be graded as low as N28.
Grades above N45 are very expensive and are not commonly available.
These higher grades are more sensitive to de-magnetizing
forces and temperatures, and are often kept super-cold from the
moment of magnetizing until the customer receives it.
Some are even shipped non-magnetized, and the customer
magnetizes them in their own facility.
Neodymium magnets are always "charged to the maximum" and
cannot be "pumped up" higher, but if they were subjected to
reverse fields, mechanical shocks, or high temperatures,
they can be recharged if the right equipment is available.
The buyer should pay attention to the Grade Rating of any magnet
they want to buy. Low cost magnets may not have the same "pull"
as more expensive magnets of the same size.
powerfully the individual magnet is magnetized.
The units of measure of a magnet's strength are named after
Carl Friedrich Gauss, and Hans Christian Ørsted. They were
Scientists who studied magnets in the 1700's.
Ørsted's name is re-spelled Oersted because English does not
commonly use the Danish "Ø", so to make the same sound,
English uses "Oe".
The theoretical maximum for Neodymium is Grade N64
meaning 64,000,000 Gauss-Oersteds.
"Mega" is the scientific prefix for million.
So, Grade N42 would be 42 MegaGauss-Oersteds.
This is often abbreviated as "42MGOe" .
Neodymium Supermagnets cannot obtain this full strength
at normal temperatures, but can approach it at near absolute
zero temperature.
As the alloying mixtures and manufacturing processes improve,
Neodymium Supermagnets will become available in higher grades.
I have read that grade N58 has been reached in the laboratory,
and Grade N45 is available at some magnet suppliers.
Some Neodymium magnets may be graded as low as N28.
Grades above N45 are very expensive and are not commonly available.
These higher grades are more sensitive to de-magnetizing
forces and temperatures, and are often kept super-cold from the
moment of magnetizing until the customer receives it.
Some are even shipped non-magnetized, and the customer
magnetizes them in their own facility.
Neodymium magnets are always "charged to the maximum" and
cannot be "pumped up" higher, but if they were subjected to
reverse fields, mechanical shocks, or high temperatures,
they can be recharged if the right equipment is available.
The buyer should pay attention to the Grade Rating of any magnet
they want to buy. Low cost magnets may not have the same "pull"
as more expensive magnets of the same size.
Where is a good place to buy magnets ?
Magnets4less
This site has lots of images and takes a while to load.
They also sell in small quantities, and offer good deals.
Another good place is
K&J Magnetics
This last place sells ... umm ... well ... just about everything the mad scientist could need, including the biggest Neodymium magnets around.
United Nuclear
This site has lots of images and takes a while to load.
They also sell in small quantities, and offer good deals.
Another good place is
K&J Magnetics
This last place sells ... umm ... well ... just about everything the mad scientist could need, including the biggest Neodymium magnets around.
United Nuclear
Thursday, August 14, 2008
Where can I see a magnet float ?
There is a video available here.
In this video is a very good float setup because the height of the lifting magnet and the distance between diamagnetic faces are both adjustable. It also looks quite expensive. It uses thick sheets of Pyrolytic Graphite. Less expensive setups are available from K&J Magnetics.
It would be a good challange to build your own frame, a kit containing magnets and Bismuth are available. The frame could be made from wood or plastic, or even non-magnetic metals. Many designs stack things like pennies to make the spacing between the faces, and use long screws to suspend the lifter magnet above the diamagnetic gap containing the floating magnet. The lifting magnet could even be a stack of ceramic magnets,which could be added or removed as needed, but the screw is still necessary for fine adjustment.
Here is a photo of a frame I made from scrap plastic in just a couple of days.
Here it is again with the Ceramic lifting magnets, the Bismuth Diagmagnetic pole pieces, and the floater magnet in place. I am using plastic spacers that are glued to the lower Bismuth Diamagnetic face.
I purchased the Bismuth castings and a number of Neodymiun magnets as a kit from a company called United Nuclear.
A company called K&J Magnetics sells a well made wooden frame with Pyrolytic Graphite faces and several small Neodymium magnets for the lifting and the floating magnets.
The K&J Magnetics frame has an adjusting screw for the lifter magnet, and adjustment for the gap between the diamagnetic Pyrolytic Graphite faces.
In this video is a very good float setup because the height of the lifting magnet and the distance between diamagnetic faces are both adjustable. It also looks quite expensive. It uses thick sheets of Pyrolytic Graphite. Less expensive setups are available from K&J Magnetics.
It would be a good challange to build your own frame, a kit containing magnets and Bismuth are available. The frame could be made from wood or plastic, or even non-magnetic metals. Many designs stack things like pennies to make the spacing between the faces, and use long screws to suspend the lifter magnet above the diamagnetic gap containing the floating magnet. The lifting magnet could even be a stack of ceramic magnets,which could be added or removed as needed, but the screw is still necessary for fine adjustment.
Here is a photo of a frame I made from scrap plastic in just a couple of days.
Here it is again with the Ceramic lifting magnets, the Bismuth Diagmagnetic pole pieces, and the floater magnet in place. I am using plastic spacers that are glued to the lower Bismuth Diamagnetic face.
I purchased the Bismuth castings and a number of Neodymiun magnets as a kit from a company called United Nuclear.
A company called K&J Magnetics sells a well made wooden frame with Pyrolytic Graphite faces and several small Neodymium magnets for the lifting and the floating magnets.
The K&J Magnetics frame has an adjusting screw for the lifter magnet, and adjustment for the gap between the diamagnetic Pyrolytic Graphite faces.
Tuesday, August 12, 2008
Are there Anti-Magnets ?
An anti-magnet would be something that is always repelled by a magnet.
This property is known as "Diamagnetism" and it is found in several substances.
A form of the element Carbon, called Graphite, is repelled by a magnet.
The metal Bismuth is also strongly diamagnetic.
A very thin wafer of pure graphite will float above a strong magnetic field.
Neodymium Supermagnets are powerful enough to make the graphite float.
A specially prepared type of graphite called "Pyrolytic Graphite" will float twice as high as regular pure graphite.
The strongest field is produced when four magnets are brought together on a flat piece of steel, and they are arranged
NS
SN
where N is the North face up and S is the South face up.
This is a stable arrangement of the magnets,and they will attract each other into this arrangement. The attractive forces will be very strong so it is best to slide the magnets across the metal plate towards their final position with great care.
I have found that pieces of graphite 50 thousandths of an inch thick become "weightless" and below 20 thousandths of an inch thick float well.
( this is about the thickness of the cardboard of a cerial box )
Pyrolytic graphite is expensive, but an equally thick wafer floats higher.
Bismuth is more diamagnetic than graphite, but it is a brittle metal and is much more dense than graphite. If a thin wafer could be made, it would still be too heavy to float.
It is better to float the Neodymium Supermagnet above the Bismuth, blocks of graphite can be used this way as well.
The usual arrangement is to use two blocks of the diamagnetic material and two magnets. The blocks of diamagnetic material should have flat faces. The flat faces are arranged facing each other, one above and one below the magnet to be floated, with about one tenth of an inch clearance above and below the floating magnet.
The other magnet is above the upper block and it's height is adjustable. This is often around two inches above the floating magnet. The "lifter" magnet is usually larger than the "floater" magnet and needs careful adjustment.
The "lifter" magnet attracts the "floater" magnet but as it approaches the Bismuth or Graphite upper face, it is repelled down. If the "floater" magnet drops too low it is repelled back up by the lower face. The "floater" magnet is free to bob and spin freely between the diamagnetic faces.
This property is known as "Diamagnetism" and it is found in several substances.
A form of the element Carbon, called Graphite, is repelled by a magnet.
The metal Bismuth is also strongly diamagnetic.
A very thin wafer of pure graphite will float above a strong magnetic field.
Neodymium Supermagnets are powerful enough to make the graphite float.
A specially prepared type of graphite called "Pyrolytic Graphite" will float twice as high as regular pure graphite.
The strongest field is produced when four magnets are brought together on a flat piece of steel, and they are arranged
NS
SN
where N is the North face up and S is the South face up.
This is a stable arrangement of the magnets,and they will attract each other into this arrangement. The attractive forces will be very strong so it is best to slide the magnets across the metal plate towards their final position with great care.
I have found that pieces of graphite 50 thousandths of an inch thick become "weightless" and below 20 thousandths of an inch thick float well.
( this is about the thickness of the cardboard of a cerial box )
Pyrolytic graphite is expensive, but an equally thick wafer floats higher.
Bismuth is more diamagnetic than graphite, but it is a brittle metal and is much more dense than graphite. If a thin wafer could be made, it would still be too heavy to float.
It is better to float the Neodymium Supermagnet above the Bismuth, blocks of graphite can be used this way as well.
The usual arrangement is to use two blocks of the diamagnetic material and two magnets. The blocks of diamagnetic material should have flat faces. The flat faces are arranged facing each other, one above and one below the magnet to be floated, with about one tenth of an inch clearance above and below the floating magnet.
The other magnet is above the upper block and it's height is adjustable. This is often around two inches above the floating magnet. The "lifter" magnet is usually larger than the "floater" magnet and needs careful adjustment.
The "lifter" magnet attracts the "floater" magnet but as it approaches the Bismuth or Graphite upper face, it is repelled down. If the "floater" magnet drops too low it is repelled back up by the lower face. The "floater" magnet is free to bob and spin freely between the diamagnetic faces.
What is a Ceramic Magnet ?
A ceramic is a powdery substance that has been bonded to make a solid object.
The powders are usually metal Oxides, and often require a very high temperature to make them solid.
Most ceramics are very hard, so they are pressed in molds to their desired shape before being bonded.
About sixty years ago it was found thst some magnetic powders could be bonded to make magnets that were very powerful. The best of these mixtures used either Barium or Stronium compounds mixed with Iron.
These ceramic magnets stayed magnetized at high temperatures and other stressful conditions. They were good for making small but powerful electric motors.
Ceramic powders were also used to make magnetic recording tape, credit cards, and "refrigerator magnets"
Refrigerator magnets are thin flexible magnets that stick to refrigerators and other appliances, and also stick to most automobiles.
The very best ceramic msgnets are about half as strong as Neodymium magnets.
Neodymium supermagnets are used where ceramic magnets will be too large, or not strong enough, as in modern computer disk drives. and in small earphones.
Monday, August 11, 2008
What is a Magnet ?
The simple answer is "A thing that attracts only Iron and other magnetic materials"
Iron is not the only metal attracted to a magnet, Cobalt, and Nickel, and several other metals exibit this strange attraction in varying degrees, but Iron is the most strongly attracted. Many compounds containing these elements are also magnetic, an example is Iron rust.
Magnetic means that it will be attracted to a magnet, Scientists call this property "Ferromagnetism"
The first magnets known occurred naturally in a substance that was called Magnetite, due to it's being discovered on the Greek island of Magnesia thousands of years ago.
Magnetite is a type of stone that is a very high grade of Iron ore.
Magnetite will be attracted to a magnet, but will not always attract Iron.
It is thought that it needs to have been struck by lightening before it
becomes "Magnetized". Magnetized means that it has become a magnet, and it will now attract Iron.
Lumps of magnetite that were naturally magnetized were called "Lodestones".
It was learned that if a lodestone was allowed to turn freely, it would always try to point North.
Lodestones were the first permanent magnets, they had the ability to attract Iron and they retained this ability for a long time.
It was also learned that certain hardened pieces of Iron, if repeatedly stroked by a lodestone, would become magnetized, and would stay magnetized for a long time.
These were the first man-made magnets, and they also had the ability to point North, and to magnetize other pieces of hardened Iron.
Iron and other magnetic materials can also become temporary magnets. These items will act like a magnet when another magnet is brought nearby. But as soon as the magnet is moved away, the temporary magnetic power is lost.
Electromagnets are also temoprary magnets.
Electromagnets are an Iron core surrounded by a coil of wire.
As long as electricity flows through the wire, the Iron will be a magnet, but as soon as the electricity stops, the magnetic power is lost.
Electromagnets can be made very strong and are used to magnetize Neodymium Super Magnets.
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