Magnetic phase diagram of the ferromagnetic Kondo-lattice compoundCeAgSb2up to 80 kbar

Electrical resistivity and ac-calorimetric measurements reveal a complex magnetic phase diagram for single crystals of the ferromagnetic Kondo-lattice compound ${\mathrm{CeAgSb}}_2$ at high pressures up to 80 kbar. The ferromagnetic order at $T_C=9.6\mathrm{}\hspace{0.5em}\mathrm{K}$ at ambient pressure is completely suppressed at a critical pressure $P_C=35\mathrm{}\mathrm{kbar}.$ Another magnetic transition, possibly antiferromagnetic, found above 27 kbar, attains a maximum value $T_N\sim 6\mathrm{K}$ at 44 kbar and then appears to be completely suppressed by $\sim 50\mathrm{kbar}.$ Thermodynamic and transport measurements in the ferromagnetic state indicate an energy gap $\Delta \sim 30\mathrm{K}$ in the spin-wave excitation spectrum at ambient pressure which decreases to $\Delta \sim 10\mathrm{K}$ at $P=30\mathrm{}\mathrm{kbar}.$ No superconductivity is observed at ambient pressure above $T\sim 0.1\mathrm{K},$ under applied pressure in the ferromagnetic state $(P=28.5\mathrm{}\mathrm{kbar}),$ nor in the antiferromagnetic state $(P=33\mathrm{}-46\mathrm{kbar})$ above $0.3\mathrm{K}.$