The unit cell of a magnetic structure is determined by the propagation vector. In my opinion, a propagation vector of (001) should give the same result of (000). But I find some reports mentioned that the propagation vector for their structures are (001) or (010) or (100). What is the difference between (000) and (001)?
That depends on the crystal structure.
For example, in a simple cubic (SC) crystal (000) and (001) are identical. Along the (00L0 direction the Brillouin zone boundary is at (00 1/2).
In a body-centered cubic (BCC) crystal (001) is "forbidden" because the conventional (cubic) unit cell contains two primitive unit cells. The Brillouin zone boundary is at (001), and the next Brillouin zone center is at (002). In that case a (001) magnetic structure is an antiferromagnet where the body center point in the opposite direction to the corner of the conventional unit cell.
This is also true for the I4/mmm structure of the ThCr2Si2 structure type you mentioned in another question - my simple picture applies to the Th site.
In diffraction experiments you see (00 2n+1) peaks arising in the magnetically ordered phase, but not in the paramagnetic phase.
(100) and (010) are the same as (001) in this case, as (101) is a reciprocal lattice vector.
Hi Detlefs, can you explain some more on "In a body-centered cubic (BCC) crystal (001) is "forbidden" because the conventional (cubic) unit cell contains two primitive unit cells."
How is about face-centered cubic (FCC) crystall?
