Magnetism and Molecules

[acsinuk]

The atomic tables indicates that nearly all elements/isotopes have a magnetic moment. But can a standard magnetometer register this?? or only permanent or changing magnetism?

[Enthalpy]

Hi acsinuk,

 

many magnetometer types measure permanent fields.

 

The field of atoms is routinely observed and used. A magnetometer won't observe the field of one atom, but of many atoms, yes. At paramagnetic and diamagnetic substances, the atoms orient their fields randomly to an other so the global effect is small, but an external field orients the atoms with a small preference for one direction, and the resulting net field created by the many atoms is measured. It is the cause of the magnetic "susceptibility", perfectly accessible to our instruments. When some very sensitive experiments are made, the response to some para- and diamagnetic materials to the geomagntic field shall even be minimized.

 

Then you have ferri- and ferromagnetic materials, were the atoms orient firmly to an other within a small "Weiss" domain. The result is very strong, either as permanent magnets or as magnetic cores, and reaches 2.2T. No subtle magnetometer is necessary to observe it, since this rotates electric motors.

 

The magnetic field of a single atom is observed, but by less direct means as far as I know. It creates the 21cm radiation of neutral H atoms, the fine and hyperfine structure in atomic light spectra, and so on.

 

Wait... With a Squid we measure less than one field quantum, so we can observe the field of one single unpaired electron at the right place. Direct measure of one atom.

[swansont]

A standard technique of measuring a magnetic moment would be NMR. You can measure the precession frequency, and if you know the strength of the external field, that should tell you the magnetic moment.