First-order magnetic transition

Lelievre-Bema, E., Rouchy, J. and Ballou, R. (1994) Field induced first order magnetic transition and associated volume effect in TbMn2, J. Mag. Mag. Mar., 137, L6-L10. 

Electrical resistivity measurements on CeSb and CeBi single crystals are displayed in fig. 123 (Suzuki et al. 1981). For CeSb a sharp decrease of p versus T is observed at Tn (16.5 K), indicating a first-order magnetic transition. A shallow minimum follows around 80 K. Subtracting Pph(T), determined from the isostructural LaSb compound, reveals that p g is proportional to — In T, which is typical for a Kondo lattice (Kasuya et al. 1982). The magnetic-field dependence of the electrical resistivity of CeSb at various temperatures is given in fig. 124. 

The indicated transition pressure of 15 GPa is in agreement with the published data with shock-wave structure measurements on a 3% silicon-iron alloy, the nominal composition of Silectron. A mixed phase region from 15 to 22.5 GPa appears quite reasonable based on shock pressure-volume data. Thus, the direct measure of magnetization appears to offer a sensitive measure of characteristics of shock-induced, first-order phase transitions involving a change in magnetization. 

In equilibrium, this describes the coexistence of two different phases (solid and liquid), just as in the case of the Ising model ( hising) with the up and down magnetization phases. When h 0, one of these two phases has a priority. Therefore, a sign change of h -h induces a first-order phase transition. (Note that for modeling reasons h(T) may be assumed to depend on temperature.)... 

Fig. 5 Magnetic phase diagram of [Mn(Cp )2][Pt(tds)2] M(T) (filled diamonds) M(H) (//] (filled triangles), H (filled inverted triangles), x (T) (open circles) x (H) (open squares) Tt is the tricritical temperature I denotes the first-order MM transition II denotes a second-order transition (AF-PM phase houndary) and III denotes a higher order transitions (from a PM to a FM like state). From [45]...

Figure 2.9 The B-Tphase diagram of MnP [13] with the magnetic field along the b-axis. Three different magnetically ordered phases - ferro, fan and screw - are separated by first-order phase transitions. The transitions to the disordered paramagnetic state are of second order and given by a dashed line.

Figure 13.2 Heat capacities of (a), Hg near the melting temperature of 234.314 K showing the abrupt nature of the change in heat capacity for this first-order phase transition at this temperature [from R. H. Busey and W. F. Giauque, J. Am. Chem. Soc., 75, 61-64 (1953)] and (b), MnO showing the continuous magnetic transition (note inset). (Data obtained from Professor Brian Woodfield and co-workers at Brigham Young University.) The dashed line is an estimate of the lattice heat capacity of MnO.

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