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Abstract:
In both spinel compounds GeCo2O4 and GeNi2O4 which order
antiferromagnetically (at T-N=23.5 K and T-N1=12.13 K/T-N2=11.46 K)
with different Curie-Weiss temperatures (T-CW=80.5 K and -15 K), the
usual magnetic frustration criterion f=parallel to T-CW parallel to/T-N
> 1 is not fulfilled. Using neutron powder diffraction and
magnetization measurements up to 55 T, both compounds are found with a
close magnetic ground state at low temperature and a similar magnetic
behavior (but with a different energy scale), even though spin
anisotropy and first neighbor exchange interactions are quite
different. This magnetic behavior can be understood when considering
the main four magnetic exchange interactions. Frustration mechanisms
are then enlightened.
