# Einstein-De Hass Effect

#### hershal

I have a research project to be done and I want to know what is Einstein-De Hass Effect. It is magneto-mechanical effect, something happens on suspending iron rod in a ring magnet but i don't have any further information on it . If I can get some links which explains what is Einstien-De Hass Effect. I searched on google, but got no good results

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#### marlon

Hi, it is the Einstein de Haas-effect

If you have a ferromagnet (that is a material in which neigboring atoms tell their closest neigbors to align their spins in the same direction) and you apply an external B field to align the spins, they will add up to produce a change in angular momentum (you know : J = L+S where S is the spin and L is the angular momentum, J is the TOTAL angular momentum), manifested by the rotation of the magnet.

Here is how it goes :

S changes due to the transition from paramagnetic to ferromagnetic (all spins align). But J must remain constant and therefore L must change and this means that the specimen will rotate. You can actually observe this rotation.

The experiment is conducted by hanging some ferromagnetic specimen (that is initially in its paramagnetic state, if you will) on a small string and then applying the external magnetic field B.

regards
marlon

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#### vanesch

Staff Emeritus
Gold Member
marlon said:
Hi, it is the Einstein de Haas-effect
Aka the Einstein - Hare effect ?

#### hershal

Thanks !

marlon said:
Hi, it is the Einstein de Haas-effect

If you have a ferromagnet (that is a material in which neigboring atoms tell their closest neigbors to align their spins in the same direction) and you apply an external B field to align the spins, they will add up to produce a change in angular momentum (you know : J = L+S where S is the spin and L is the angular momentum, J is the TOTAL angular momentum), manifested by the rotation of the magnet.

regards
marlon
Thanks Marlon, If you are aware of any site that offers information about einstiein - de Hass effect or u know any other a-z physics site could you please pass me the URL

#### hershal

Home Experiment

Today, I took a transparent light weight plastic hollow cylinder ( about 3.5 cm in diameter and 15 cm in length and may be 0.5 mm thick) . Tightly coiled a wire ( simple electric wire ) around it . No. of turns are 50 . Suspend an iron rod in between ( so that it does not touch the edges of the cylinder ) with the help of a thinnest thread available at home. Iron rod is about 15.5 cm in length and 0.4 cm in diameter , quiet heavy too, with flat edges , actually its a screw driver without the plastic handle. Passed current through the coil ( 4.5 V ) ........ no effect

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