# Thermodynamics - Work done on a paramagnetic material

1. ### Cantique

5
What is the work done on a paramagnetic? I have seen both of the following:

$\hat{d}$w = -MdB
$\hat{d}$w = -BdM

Where B is magnetic field and M is magnetisation

Am I missing something here or are these two completely opposite? My text book says that -MdB is the work done but I am sure I have seen articles where they use HdM as the work done. Could somebody clear this up for me?

2. ### macdonal

1
See the paper The Form of Magnetic Work in a Fundamental Thermodynamic Equation for a Paramagnet
Am. J. Phys. 67, 613 (1999).

A copy can also be obtained at http://faculty.luther.edu/~macdonal/ .

3. ### 256bits

Do you know the relationship between B and H?

4. ### DrDu

4,102
One of the best discussions is given in Landau, Lifshitz, Vol. V, Section 31 and 32.