How to calculate saturation magnetisation in GMR effect?

1. Jun 10, 2015

majas

1. The problem statement, all variables and given/known data
Hello everyone. This is my first post.
I'm working now on my laboratory report from GMR effect. I have to calculate the antiferromagnetic coupling for my multilayers. I have only resistance versus magnetic field graphs.

2. Relevant equations
I want to use the equation:
$J_{AF}=-\frac{\mu_0 M_S t}{4}H_S$
It's easy to find $H_S$, $\mu_0$ and t is given, and I need $M_S$.

3. The attempt at a solution
I have found equation $$H_S=\frac{K}{M_S},$$ but there is next unknown K, which is the anisotropy constant, and I'm not sure how it is for permalloy which the multilayers were made.

2. Jun 10, 2015