AW: [Wien] Unit for the HFF

[Gerhard Fecher]

Thanks, this I know, however, if something is given in Gauss its rather unclear to what physical quantity it belongs, thus the problem pertains, is mu_0 included or not ?

Maybe A/m is rarely used, it is the correct unit for the field strength in SI unit.
That it was not used a lot in the past millenium does not prevent me to teach it correctly to my students, even I am agewise probably supposed to use big birds. 

Thanks again
Ciao
Gerhard


-----Ursprüngliche Nachricht-----
Von: wien-bounces at zeus.theochem.tuwien.ac.at im Auftrag von thomas.mazet
Gesendet: Sa 04.02.2006 13:43
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] Unit for the HFF
 

Dear Gerhard,

I'm just a user ...and units in magnetism are "complicated"

- In cgs-emu units :
B (magnetic induction) is in gauss (G)
H (magnetic field) is in Oersted (Oe)
and in cgs-emu B = H (+ 4pi.M) [M is the magnetization in ... emu !]
B and H have the same dimension but different units
and 1 G = 1 Oe

- In Si units :
B is in T [= N/(A.m)]
H is in A/m
here B and H have different dimensions and different units

B = muO.H (+ mu0.M) [- M is the magnetization in A/m
                     - mu0 is the permeability of vacuum
                     - mu0 = 4pi 10^-7 H/m (or N/A^2)] 

Conversion between SI and cgs-emu :
 1 T = 10^4 G (= 10^4 Oe)
 1 A/m = 4pi/10^3 Oe (= 4pi/10^3 G)

To summarize :
The output HFF (HyperFine Field) in Wien is given in kGauss (B in cgs-emu 
units but is equivalent to H in kOe)
if you want to convert in SI units you divide by 10
and you obtain B or mu0.H  in T
if you want H in A/m you divide this later value by mu0=4pi.10^-7....

To my knowledge, A/m is rarely used to express HFF at the nucleus and 
often peoples are 
not very rigourous about the terminology (magnetic field H/magnetic 
induction B) and about the units (G, Oe, T).

I'm sure it is not quite clear ... but, nevertheless, I hope it helps.

Thomas 



> I was wondering about the unit used for the hyperfine field (HFF values). 
Unfortunately, the values are given in multiples of big birds (emu). 
I wonder why it is Gauss for the flux density (B) 
and not Oerstett for the magnetic field strength (H). 
Seems it would be better to use SI units (A/m).
> 
> Anyway, I wonder if the values given include a factor of 4Pi 
or not as field strength and flux density and their units are 
usually muddled up in emu. 
So is the last F for Hyperfine Flux or Hyperfine Field 
and how to transform the unit correctly to SI ?
> 
> Thanks a lot for enlightenments
> Ciao
> Gerhard
> 

-- 
Thomas MAZET
Laboratoire de Chimie du Solide Minéral (UMR 7555)
Université Henri Poincaré-Nancy I
BP 239 54506 Vandoeuvre les Nancy Cedex
FRANCE
Tel.: +33-(0)3-83-68-46-77
Fax : +33-(0)3-83-68-46-11


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