Abstrakt
Themetamagnetic transition between the antiferromagnetic and paramagnetic state in UIrGe has been studied at various temperatures bymagnetization, heat capacity, and magnetocaloric-effect measurements on a single crystal in static and pulsed magnetic fields applied along the orthorhombic b axis. A first-order transition is observed at temperatures below13Kand a second-order one at higher temperatures up to the Neel temperature (T-N = 16.5K).
The first-order transition is accompanied by a dramatic increase of the Sommerfeld coefficient. Magnetization measurements extended to the paramagnetic range revealed an anomalous S shape (inflection point at a magnetic field H-m) in magnetization isotherms at temperatures above 13 K and a temperature dependence of susceptibility with a maximum at T-max well above TN.
The lines representing the temperature-induced evolution of Hm and field-induced evolution of T-max, respectively, are bound for the point in the magnetic phase diagram at which the order of metamagnetic transition changes. A tentative scenario explaining these anomalies by antiferromagnetic correlations or short-range order in the paramagnetic state is discussed.