The thermal expansion and specific heat measurements under ambient pressure and the thermomagnetization measurement under applied pressure for new Lu 6 (Mn 1-x Fe x ) 23 compounds have been carried out in order to discuss the relationship between the thermal expansion anomaly and the spin fluctuations. The thermal expansion coefficient α significantly increases above the Curie temperature T C . The electronic specific heat coefficient increases with increasing x, accompanied by the decrease of the spin fluctuation spectral width. The value of the pressure dependence of T C , ∂T C /∂ P, is large at about -50 K GPa -1 . The anti-invar effect and the pressure effect of T C are closely related to a significant thermal variation of the amplitude of spin fluctuations.
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