Specific heat CeNiSn

Izawa et al. (1996) explained the field dependence of specific heat with the help of a modified pseudo-gap to rxdiich a residual flat DOS at had been added (see fig. 107). This model also nrakes possible an explanation of the resistivity data for CeNiSn materials of different impurity content (Ikeda and Miyake 1996). It was foimd that the DOS inside the gap at Ef increases with imprrrity content. Furthermore, gap anisotropy could be derived from the Ifc-dependence of the (ce- f)-hybridization matrix element. 

The formation of the dielectric gap leads to a sharp increase of resistivity below 10 K and to a decrease of the specific heat coefficient below 5 K. The value of y for CeNiSn is much bigger than that of LaNiSn (265 and 25 mJ/(K mol), respectively, at 5 K) (Aliev et al. 1988b). 

To clarify the origin of maximum in x> the specific heat C has been measured imder pressure up to 0.37 GPa. The temperature dependencies of C of CeNiSn at several pressures parallel to the a-, b-, and c-axes are shown in Figure 132. For P//a-axis, the value of C decreases slightly with pressure in the temperature range of the measurements. By contrast, for P//b-axis and P//c-axis, C increases with pressure and shows a maximum around 3.7 K at 0.25 and 0.13 GPa, respectively. With further increase in pressure, another peak appears around 3 K. 

FIGURE 132 Specific heat C of CeNiSn as a function of T under uniaxial pressure (Umeo et al 1999). 

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