The unusual width of the (101) and (102) magnetic reflections of antiferromagnetic K2NiF4 shows the existence of stacking faults in the piling up of the antiferromagnetic sheets. The probabilities of such faults at various temperatures are determined and show an increase with temperature. It is then shown that lowering of the free energy is obtained by considering exchange striction from a slight orthorhombic distortion; ungrouped stacking faults lead to an additional lowering of the free energy.

Topics
Free energy, Crystallographic defects, Neutron scattering
1.
E.
Legrand
 and
R.
Plumier
,
Physica Status Solidi
2
,
317
(
1962
).
Google Scholar
Crossref
Search ADS
 
2.
R.
Plumier
 and
E.
Legrand
,
J. Phys. Radium
23
,
474
(
1962
).
Google Scholar
Crossref
Search ADS
 
3.
R.
Plumier
,
J. Phys. Radium
24
,
741
(
1963
).
Google Scholar
Crossref
Search ADS
 
4.
A. J.
Wilson
,
Proc. Roy. Soc. (London)
A180
,
277
(
1942
).
Google Scholar
 
5.
As a result of Eq. (3), the (100) reflection is not affected by stacking faults. However, as may be seen from Fig. 2, it has the expected4 saw‐tooth shape.
6.
Such a deformation could not be found by x‐ray diffraction experiments performed at 85 °K. We assumed for the upper limit of the deformation dx/(a/2) = −dy/(a/2) = exx = eyy = 0.5×10−4.
This content is only available via PDF.
© 1964 The American Institute of Physics.
1964
The American Institute of Physics
You do not currently have access to this content.