Enhancement of isothermal entropy change due to spin fluctuations in itinerant-electron metamagnetic La(Fe0.88Si0.12)13 compound

A large isothermal entropy change in La(Fe0.88Si0.12)13 itinerant-electron metamagnetic (IEM) compound has been investigated by using the Maxwell and Clausius–Clapeyron relations. The entropy change obtained from the Clausius–Clapeyron relation ΔSmCC gradually decreases with increasing temperature, while that from the Maxwell relation ΔSmMx in the magnetic field of 2 T shows a plateau-like behavior in 195–203 K. The difference between ΔSmMx and ΔSmCC is mainly explained by the entropy change in the paramagnetic (P) state below the critical magnetic field of the IEM transition BC. In the P state, the temperature dependence of susceptibility χp is enhanced by spin fluctuations. The thermal variation of ΔSmMx−ΔSmCC is well represented by taking that of χp as well as BC into account. Therefore, the plateau-like behavior of ΔSmMx comes from the enhancement of the entropy change in the P state, which cancels the decrease of ΔSmCC due to the decrease of latent heat of the IEM transition with increasing temperature.