Thermal expansion and compressibility of monogermanides of 3d-metals

Synchrotron diffraction as a function of temperature and pressure, specific heat, magnetic susceptibility and small-angle neutron scattering experiments have revealed an anomalous response of MnGe. Similar but less pronounced behavior has also been observed in Mn$_{1-x}$Co$_x$Ge and Mn$_{1-x}$Fe$_x$Ge solid solutions. Spin density fluctuations and Mn spin state instability are discussed as possible candidates for the observed effects.