Magnetism in the S= 1 frustrated antiferromagnet GeNi2O4 studied using implanted muons

We present the results of a muon-spin relaxation study of $\mathrm{Ge}{\mathrm{Ni}}_{2}{\mathrm{O}}_{4}$. We provide further clarification of the two transitions to the antiferromagnetic state and measure the magnetic field dependence of the heat capacity up to $14\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. Both oscillatory and relaxing signals are observed below the lower transition (at temperature ${T}_{\mathrm{N}2}$) in the muon-decay positron asymmetry spectra, arising from two distinct types of magnetic environment. A possible explanation is suggested in terms of the separate ordering of two magnetic subsystems, one of which does not order fully down to the lowest measured temperature $(1.8\phantom{\rule{0.3em}{0ex}}\mathrm{K})$.