# Langevin curve fitting

1. Jun 24, 2008

### mhill

hi, there my question is let's suppose we have the magnetization (M) versus the applied field (H) as

$$M(H,T)= \sum _{n=1}^{N} W(x_i ) (x_i ) Lang (H.A.x_{i}/T)$$

here 'A' is a constant 'T' is the temperature of system Lang(x) is the Langevin function coth(x)-1/x ,

My problem is how to use a curve fitting algorithm to solve the problem ,i am working under the assumption that $$W(x_i)$$ i=1,2,3,....,N is a log normal distribution depending only on the value x_i

my curve fitting program is just 'Origin 7' i need the algorithm to curve-fitting to a certain given distribution W(x) thanks.

P.D in case you see this post in another forum, sorry i made a mistake erase this post and keep only the one made in the 'programming' forum.