Magnetovolume anomalies in Ce2 Fe17-x Mn x

Анотація

The small nonmonotonic changes of the lattice parameters upon the substitution of Mn for Fe in Ce₂Fe₁₇ lead to significant changes of the magnetic properties. In order to determine the role of the volume, we made ac susceptibility and thermal expansion measurements on the polycrystalline compounds Ce₂Fe_16.65Mn_0.35 and Ce₂Fe₁₆Mn₁ under hydrostatic pressure up to 10 kbar in the temperature range 10-300 K. The substitution of Mn for Fe leads to significant narrowing of the range of stability of the low-temperature ferromagnetic phase characterized by Q _T =48 K (x=0.35) in comparison with binary Ce₂Fe₁7, where Q _T =94 K. Applying a relatively small pressure of 1.5 kbar leads to suppression of both the ferromagnetic order and large positive spontaneous volume magnetostriction in Ce₂Fe_16.5Mn_0.35. The pressure effect on Q _T is significant, dQ _T / dp=-30 K/kbar. The effect of pressure on the Néel temperature is moderate and slightly increases with increasing Mn content (dT _N / dp= -2.2 K/kbar for Ce₂Fe_16.65 Mn_0.35). No ferromagnetic order was observed in Ce₂Fe₁₆Mn₁ at ambient pressure, but an unexpected reentering increase of the ac susceptibility was detected at pressures 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.