Is there a place where I can download some good XANES standards for these samples? I know that this has been a problem for some time and I have found in the literature recent articles which show different XANES spectra for the "same" iron oxide, so I was wondering about this.

The only one I have managed to find is hematite: 
http://cars9.uchicago.edu/~ravel/software/doc/Standards/fe.html 

Thanks in advance,

Javier