Magnetovolume anomalies in Ce2Fe17-xMnx

The small nonmonotonic changes of the lattice parameters upon the substitut ion of Mn for Fe in Ce2Fe17 lead to significant changes of the magnetic pro perties. In order to determine the role of the volume, we made ac susceptib ility and thermal expansion measurements on the polycrystalline compounds C e2Fe16.65Mn0.35 and Ce2Fe16Mn1 under hydrostatic pressure up to 10 kbar in the temperature range 10-300 K. The substitution of Mn for Fe leads to sign ificant narrowing of the range of stability of the low-temperature ferromag netic phase characterized by Theta (T)=48 K (x=0.35) in comparison with bin ary Ce2Fe17, where Theta (T)=94 K. Applying a relatively small pressure of 1.5 kbar leads to suppression of both the ferromagnetic order and large pos itive spontaneous volume magnetostriction in Ce2Fe16.5Mn0.35. The pressure effect on Theta (T) is significant, d Theta (T)/dp=-30 K/kbar. The effect o f pressure on the Neel temperature is moderate and increases slightly, with increasing Mn content (dT(N)/dp=-2.2 K/kbar for Ce2Fe16.65Mn0.35). No ferr omagnetic order was observed in Ce2Fe16Mn1 at ambient pressure, but an unex pected reentrant increase of the ac susceptibility was detected at pressure s higher than 1.5 kbar below 50 K. It indicates the existence of a pressure -induced ferromagnetic phase at low temperature. The results show not only a strong correlation between the magnetic properties and the lattice volume but also a significant role of the Mn content. (C) 2001 American Institute of Physics.